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66
.gitignore
vendored
66
.gitignore
vendored
@ -1,34 +1,34 @@
|
||||
# Compiled Object files, Static and Dynamic libs (Shared Objects)
|
||||
*.o
|
||||
*.a
|
||||
*.so
|
||||
|
||||
# Folders
|
||||
_obj
|
||||
_test
|
||||
|
||||
# Architecture specific extensions/prefixes
|
||||
*.[568vq]
|
||||
[568vq].out
|
||||
|
||||
*.cgo1.go
|
||||
*.cgo2.c
|
||||
_cgo_defun.c
|
||||
_cgo_gotypes.go
|
||||
_cgo_export.*
|
||||
|
||||
_testmain.go
|
||||
|
||||
*.prof
|
||||
# Test binary, build with `go test -c`
|
||||
*.test
|
||||
# Binaries for programs and plugins
|
||||
*.exe
|
||||
*.dll
|
||||
*.dylib
|
||||
|
||||
# JetBrains project files
|
||||
.idea/
|
||||
|
||||
# Output of the go coverage tool, specifically when used with LiteIDE
|
||||
# Compiled Object files, Static and Dynamic libs (Shared Objects)
|
||||
*.o
|
||||
*.a
|
||||
*.so
|
||||
|
||||
# Folders
|
||||
_obj
|
||||
_test
|
||||
|
||||
# Architecture specific extensions/prefixes
|
||||
*.[568vq]
|
||||
[568vq].out
|
||||
|
||||
*.cgo1.go
|
||||
*.cgo2.c
|
||||
_cgo_defun.c
|
||||
_cgo_gotypes.go
|
||||
_cgo_export.*
|
||||
|
||||
_testmain.go
|
||||
|
||||
*.prof
|
||||
# Test binary, build with `go test -c`
|
||||
*.test
|
||||
# Binaries for programs and plugins
|
||||
*.exe
|
||||
*.dll
|
||||
*.dylib
|
||||
|
||||
# JetBrains project files
|
||||
.idea/
|
||||
|
||||
# Output of the go coverage tool, specifically when used with LiteIDE
|
||||
*.out
|
||||
50
.travis.yml
50
.travis.yml
@ -1,25 +1,25 @@
|
||||
language: node_js
|
||||
|
||||
env:
|
||||
global:
|
||||
- GH_REPO="github.com/tmrts/go-patterns"
|
||||
- secure: 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
|
||||
|
||||
install:
|
||||
- npm install gitbook-cli
|
||||
- gitbook install
|
||||
|
||||
script:
|
||||
- gitbook build . out
|
||||
|
||||
after_success:
|
||||
- echo -e "Deploying updates to GitHub..."
|
||||
- MSG=$(git log -1 --oneline)
|
||||
- cd out
|
||||
- git config --global user.email "contact@tmrts.com"
|
||||
- git config --global user.name "Tamer Tas"
|
||||
- git init
|
||||
- git checkout -b gh-pages
|
||||
- git add -A :/
|
||||
- git commit -m "Travis CI | ${MSG}"
|
||||
- git push "https://${GH_TOKEN}@${GH_REPO}" gh-pages -f
|
||||
language: node_js
|
||||
|
||||
env:
|
||||
global:
|
||||
- GH_REPO="github.com/tmrts/go-patterns"
|
||||
- secure: 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
|
||||
|
||||
install:
|
||||
- npm install gitbook-cli
|
||||
- gitbook install
|
||||
|
||||
script:
|
||||
- gitbook build . out
|
||||
|
||||
after_success:
|
||||
- echo -e "Deploying updates to GitHub..."
|
||||
- MSG=$(git log -1 --oneline)
|
||||
- cd out
|
||||
- git config --global user.email "contact@tmrts.com"
|
||||
- git config --global user.name "Tamer Tas"
|
||||
- git init
|
||||
- git checkout -b gh-pages
|
||||
- git add -A :/
|
||||
- git commit -m "Travis CI | ${MSG}"
|
||||
- git push "https://${GH_TOKEN}@${GH_REPO}" gh-pages -f
|
||||
|
||||
@ -1,31 +1,31 @@
|
||||
# Contribution Guidelines
|
||||
|
||||
Please ensure your pull request adheres to the following guidelines:
|
||||
|
||||
- Make an individual pull request for each suggestion.
|
||||
- Choose the corresponding patterns section for your suggestion.
|
||||
- List, after your addition, should be in lexicographical order.
|
||||
|
||||
## Commit Messages Guidelines
|
||||
|
||||
- The message should be in imperative form and uncapitalized.
|
||||
- If possible, please include an explanation in the commit message body
|
||||
- Use the form `<pattern-section>/<pattern-name>: <message>` (e.g. `creational/singleton: refactor singleton constructor`)
|
||||
|
||||
## Pattern Template
|
||||
|
||||
Each pattern should have a single markdown file containing the important part of the implementation, the usage and the explanations for it. This is to ensure that the reader doesn't have to read bunch of boilerplate to understand what's going on and the code is as simple as possible and not simpler.
|
||||
|
||||
Please use the following template for adding new patterns:
|
||||
|
||||
```markdown
|
||||
# <Pattern-Name>
|
||||
<Pattern description>
|
||||
|
||||
## Implementation
|
||||
|
||||
## Usage
|
||||
|
||||
// Optional
|
||||
## Rules of Thumb
|
||||
```
|
||||
# Contribution Guidelines
|
||||
|
||||
Please ensure your pull request adheres to the following guidelines:
|
||||
|
||||
- Make an individual pull request for each suggestion.
|
||||
- Choose the corresponding patterns section for your suggestion.
|
||||
- List, after your addition, should be in lexicographical order.
|
||||
|
||||
## Commit Messages Guidelines
|
||||
|
||||
- The message should be in imperative form and uncapitalized.
|
||||
- If possible, please include an explanation in the commit message body
|
||||
- Use the form `<pattern-section>/<pattern-name>: <message>` (e.g. `creational/singleton: refactor singleton constructor`)
|
||||
|
||||
## Pattern Template
|
||||
|
||||
Each pattern should have a single markdown file containing the important part of the implementation, the usage and the explanations for it. This is to ensure that the reader doesn't have to read bunch of boilerplate to understand what's going on and the code is as simple as possible and not simpler.
|
||||
|
||||
Please use the following template for adding new patterns:
|
||||
|
||||
```markdown
|
||||
# <Pattern-Name>
|
||||
<Pattern description>
|
||||
|
||||
## Implementation
|
||||
|
||||
## Usage
|
||||
|
||||
// Optional
|
||||
## Rules of Thumb
|
||||
```
|
||||
|
||||
352
LICENSE
352
LICENSE
@ -1,176 +1,176 @@
|
||||
Apache License
|
||||
Version 2.0, January 2004
|
||||
http://www.apache.org/licenses/
|
||||
|
||||
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
|
||||
|
||||
1. Definitions.
|
||||
|
||||
"License" shall mean the terms and conditions for use, reproduction,
|
||||
and distribution as defined by Sections 1 through 9 of this document.
|
||||
|
||||
"Licensor" shall mean the copyright owner or entity authorized by
|
||||
the copyright owner that is granting the License.
|
||||
|
||||
"Legal Entity" shall mean the union of the acting entity and all
|
||||
other entities that control, are controlled by, or are under common
|
||||
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|
||||
"control" means (i) the power, direct or indirect, to cause the
|
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direction or management of such entity, whether by contract or
|
||||
otherwise, or (ii) ownership of fifty percent (50%) or more of the
|
||||
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|
||||
|
||||
"You" (or "Your") shall mean an individual or Legal Entity
|
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|
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|
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"Source" form shall mean the preferred form for making modifications,
|
||||
including but not limited to software source code, documentation
|
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source, and configuration files.
|
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|
||||
"Object" form shall mean any form resulting from mechanical
|
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transformation or translation of a Source form, including but
|
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not limited to compiled object code, generated documentation,
|
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and conversions to other media types.
|
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|
||||
"Work" shall mean the work of authorship, whether in Source or
|
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Object form, made available under the License, as indicated by a
|
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copyright notice that is included in or attached to the work
|
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|
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|
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"Derivative Works" shall mean any work, whether in Source or Object
|
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|
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editorial revisions, annotations, elaborations, or other modifications
|
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|
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|
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separable from, or merely link (or bind by name) to the interfaces of,
|
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the Work and Derivative Works thereof.
|
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"Contribution" shall mean any work of authorship, including
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the original version of the Work and any modifications or additions
|
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|
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submitted to Licensor for inclusion in the Work by the copyright owner
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|
||||
END OF TERMS AND CONDITIONS
|
||||
Apache License
|
||||
Version 2.0, January 2004
|
||||
http://www.apache.org/licenses/
|
||||
|
||||
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
|
||||
|
||||
1. Definitions.
|
||||
|
||||
"License" shall mean the terms and conditions for use, reproduction,
|
||||
and distribution as defined by Sections 1 through 9 of this document.
|
||||
|
||||
"Licensor" shall mean the copyright owner or entity authorized by
|
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the copyright owner that is granting the License.
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||||
|
||||
"Legal Entity" shall mean the union of the acting entity and all
|
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other entities that control, are controlled by, or are under common
|
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control with that entity. For the purposes of this definition,
|
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"control" means (i) the power, direct or indirect, to cause the
|
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direction or management of such entity, whether by contract or
|
||||
otherwise, or (ii) ownership of fifty percent (50%) or more of the
|
||||
outstanding shares, or (iii) beneficial ownership of such entity.
|
||||
|
||||
"You" (or "Your") shall mean an individual or Legal Entity
|
||||
exercising permissions granted by this License.
|
||||
|
||||
"Source" form shall mean the preferred form for making modifications,
|
||||
including but not limited to software source code, documentation
|
||||
source, and configuration files.
|
||||
|
||||
"Object" form shall mean any form resulting from mechanical
|
||||
transformation or translation of a Source form, including but
|
||||
not limited to compiled object code, generated documentation,
|
||||
and conversions to other media types.
|
||||
|
||||
"Work" shall mean the work of authorship, whether in Source or
|
||||
Object form, made available under the License, as indicated by a
|
||||
copyright notice that is included in or attached to the work
|
||||
(an example is provided in the Appendix below).
|
||||
|
||||
"Derivative Works" shall mean any work, whether in Source or Object
|
||||
form, that is based on (or derived from) the Work and for which the
|
||||
editorial revisions, annotations, elaborations, or other modifications
|
||||
represent, as a whole, an original work of authorship. For the purposes
|
||||
of this License, Derivative Works shall not include works that remain
|
||||
separable from, or merely link (or bind by name) to the interfaces of,
|
||||
the Work and Derivative Works thereof.
|
||||
|
||||
"Contribution" shall mean any work of authorship, including
|
||||
the original version of the Work and any modifications or additions
|
||||
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|
||||
submitted to Licensor for inclusion in the Work by the copyright owner
|
||||
or by an individual or Legal Entity authorized to submit on behalf of
|
||||
the copyright owner. For the purposes of this definition, "submitted"
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END OF TERMS AND CONDITIONS
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||||
220
README.md
220
README.md
@ -1,110 +1,110 @@
|
||||
<p align="center">
|
||||
<img src="/gopher.png" height="400">
|
||||
<h1 align="center">
|
||||
Go Patterns
|
||||
<br>
|
||||
<a href="http://travis-ci.org/tmrts/go-patterns"><img alt="build-status" src="https://img.shields.io/badge/build-passing-brightgreen.svg?style=flat-square" /></a>
|
||||
<a href="https://github.com/sindresorhus/awesome" ><img alt="awesome" src="https://img.shields.io/badge/awesome-%E2%9C%93-ff69b4.svg?style=flat-square" /></a>
|
||||
<a href="https://github.com/tmrts/go-patterns/blob/master/LICENSE" ><img alt="license" src="https://img.shields.io/badge/license-Apache%20License%202.0-E91E63.svg?style=flat-square" /></a>
|
||||
</h1>
|
||||
</p>
|
||||
|
||||
A curated collection of idiomatic design & application patterns for Go language.
|
||||
|
||||
## Creational Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Abstract Factory](/creational/abstract_factory.md) | Provides an interface for creating families of releated objects | ✘ |
|
||||
| [Builder](/creational/builder.md) | Builds a complex object using simple objects | ✔ |
|
||||
| [Factory Method](/creational/factory.md) | Defers instantiation of an object to a specialized function for creating instances | ✔ |
|
||||
| [Object Pool](/creational/object-pool.md) | Instantiates and maintains a group of objects instances of the same type | ✔ |
|
||||
| [Singleton](/creational/singleton.md) | Restricts instantiation of a type to one object | ✔ |
|
||||
|
||||
## Structural Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Bridge](/structural/bridge.md) | Decouples an interface from its implementation so that the two can vary independently | ✘ |
|
||||
| [Composite](/structural/composite.md) | Encapsulates and provides access to a number of different objects | ✘ |
|
||||
| [Decorator](/structural/decorator.md) | Adds behavior to an object, statically or dynamically | ✔ |
|
||||
| [Facade](/structural/facade.md) | Uses one type as an API to a number of others | ✘ |
|
||||
| [Flyweight](/structural/flyweight.md) | Reuses existing instances of objects with similar/identical state to minimize resource usage | ✘ |
|
||||
| [Proxy](/structural/proxy.md) | Provides a surrogate for an object to control it's actions | ✔ |
|
||||
|
||||
## Behavioral Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Chain of Responsibility](/behavioral/chain_of_responsibility.md) | Avoids coupling a sender to receiver by giving more than object a chance to handle the request | ✘ |
|
||||
| [Command](/behavioral/command.md) | Bundles a command and arguments to call later | ✘ |
|
||||
| [Mediator](/behavioral/mediator.md) | Connects objects and acts as a proxy | ✘ |
|
||||
| [Memento](/behavioral/memento.md) | Generate an opaque token that can be used to go back to a previous state | ✘ |
|
||||
| [Observer](/behavioral/observer.md) | Provide a callback for notification of events/changes to data | ✔ |
|
||||
| [Registry](/behavioral/registry.md) | Keep track of all subclasses of a given class | ✘ |
|
||||
| [State](/behavioral/state.md) | Encapsulates varying behavior for the same object based on its internal state | ✘ |
|
||||
| [Strategy](/behavioral/strategy.md) | Enables an algorithm's behavior to be selected at runtime | ✔ |
|
||||
| [Template](/behavioral/template.md) | Defines a skeleton class which defers some methods to subclasses | ✘ |
|
||||
| [Visitor](/behavioral/visitor.md) | Separates an algorithm from an object on which it operates | ✘ |
|
||||
|
||||
## Synchronization Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Condition Variable](/synchronization/condition_variable.md) | Provides a mechanism for threads to temporarily give up access in order to wait for some condition | ✘ |
|
||||
| [Lock/Mutex](/synchronization/mutex.md) | Enforces mutual exclusion limit on a resource to gain exclusive access | ✘ |
|
||||
| [Monitor](/synchronization/monitor.md) | Combination of mutex and condition variable patterns | ✘ |
|
||||
| [Read-Write Lock](/synchronization/read_write_lock.md) | Allows parallel read access, but only exclusive access on write operations to a resource | ✘ |
|
||||
| [Semaphore](/synchronization/semaphore.md) | Allows controlling access to a common resource | ✔ |
|
||||
|
||||
## Concurrency Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [N-Barrier](/concurrency/barrier.md) | Prevents a process from proceeding until all N processes reach to the barrier | ✘ |
|
||||
| [Bounded Parallelism](/concurrency/bounded_parallelism.md) | Completes large number of independent tasks with resource limits | ✔ |
|
||||
| [Broadcast](/concurrency/broadcast.md) | Transfers a message to all recipients simultaneously | ✘ |
|
||||
| [Coroutines](/concurrency/coroutine.md) | Subroutines that allow suspending and resuming execution at certain locations | ✘ |
|
||||
| [Generators](/concurrency/generator.md) | Yields a sequence of values one at a time | ✔ |
|
||||
| [Reactor](/concurrency/reactor.md) | Demultiplexes service requests delivered concurrently to a service handler and dispatches them syncronously to the associated request handlers | ✘ |
|
||||
| [Parallelism](/concurrency/parallelism.md) | Completes large number of independent tasks | ✔ |
|
||||
| [Producer Consumer](/concurrency/producer_consumer.md) | Separates tasks from task executions | ✘ |
|
||||
|
||||
## Messaging Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Fan-In](/messaging/fan_in.md) | Funnels tasks to a work sink (e.g. server) | ✔ |
|
||||
| [Fan-Out](/messaging/fan_out.md) | Distributes tasks among workers (e.g. producer) | ✔ |
|
||||
| [Futures & Promises](/messaging/futures_promises.md) | Acts as a place-holder of a result that is initially unknown for synchronization purposes | ✘ |
|
||||
| [Publish/Subscribe](/messaging/publish_subscribe.md) | Passes information to a collection of recipients who subscribed to a topic | ✔ |
|
||||
| [Push & Pull](/messaging/push_pull.md) | Distributes messages to multiple workers, arranged in a pipeline | ✘ |
|
||||
|
||||
## Stability Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Bulkheads](/stability/bulkhead.md) | Enforces a principle of failure containment (i.e. prevents cascading failures) | ✘ |
|
||||
| [Circuit-Breaker](/stability/circuit-breaker.md) | Stops the flow of the requests when requests are likely to fail | ✔ |
|
||||
| [Deadline](/stability/deadline.md) | Allows clients to stop waiting for a response once the probability of response becomes low (e.g. after waiting 10 seconds for a page refresh) | ✘ |
|
||||
| [Fail-Fast](/stability/fail_fast.md) | Checks the availability of required resources at the start of a request and fails if the requirements are not satisfied | ✘ |
|
||||
| [Handshaking](/stability/handshaking.md) | Asks a component if it can take any more load, if it can't, the request is declined | ✘ |
|
||||
| [Steady-State](/stability/steady_state.md) | For every service that accumulates a resource, some other service must recycle that resource | ✘ |
|
||||
|
||||
## Profiling Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Timing Functions](/profiling/timing.md) | Wraps a function and logs the execution | ✔ |
|
||||
|
||||
## Idioms
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Functional Options](/idiom/functional-options.md) | Allows creating clean APIs with sane defaults and idiomatic overrides | ✔ |
|
||||
|
||||
## Anti-Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Cascading Failures](/anti-patterns/cascading_failures.md) | A failure in a system of interconnected parts in which the failure of a part causes a domino effect | ✘ |
|
||||
<p align="center">
|
||||
<img src="/gopher.png" height="400">
|
||||
<h1 align="center">
|
||||
Go Patterns
|
||||
<br>
|
||||
<a href="http://travis-ci.org/tmrts/go-patterns"><img alt="build-status" src="https://img.shields.io/badge/build-passing-brightgreen.svg?style=flat-square" /></a>
|
||||
<a href="https://github.com/sindresorhus/awesome" ><img alt="awesome" src="https://img.shields.io/badge/awesome-%E2%9C%93-ff69b4.svg?style=flat-square" /></a>
|
||||
<a href="https://github.com/tmrts/go-patterns/blob/master/LICENSE" ><img alt="license" src="https://img.shields.io/badge/license-Apache%20License%202.0-E91E63.svg?style=flat-square" /></a>
|
||||
</h1>
|
||||
</p>
|
||||
|
||||
A curated collection of idiomatic design & application patterns for Go language.
|
||||
|
||||
## Creational Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Abstract Factory](/creational/abstract_factory.md) | Provides an interface for creating families of releated objects | ✘ |
|
||||
| [Builder](/creational/builder.md) | Builds a complex object using simple objects | ✔ |
|
||||
| [Factory Method](/creational/factory.md) | Defers instantiation of an object to a specialized function for creating instances | ✔ |
|
||||
| [Object Pool](/creational/object-pool.md) | Instantiates and maintains a group of objects instances of the same type | ✔ |
|
||||
| [Singleton](/creational/singleton.md) | Restricts instantiation of a type to one object | ✔ |
|
||||
|
||||
## Structural Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Bridge](/structural/bridge.md) | Decouples an interface from its implementation so that the two can vary independently | ✘ |
|
||||
| [Composite](/structural/composite.md) | Encapsulates and provides access to a number of different objects | ✘ |
|
||||
| [Decorator](/structural/decorator.md) | Adds behavior to an object, statically or dynamically | ✔ |
|
||||
| [Facade](/structural/facade.md) | Uses one type as an API to a number of others | ✘ |
|
||||
| [Flyweight](/structural/flyweight.md) | Reuses existing instances of objects with similar/identical state to minimize resource usage | ✘ |
|
||||
| [Proxy](/structural/proxy.md) | Provides a surrogate for an object to control it's actions | ✔ |
|
||||
|
||||
## Behavioral Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Chain of Responsibility](/behavioral/chain_of_responsibility.md) | Avoids coupling a sender to receiver by giving more than object a chance to handle the request | ✘ |
|
||||
| [Command](/behavioral/command.md) | Bundles a command and arguments to call later | ✘ |
|
||||
| [Mediator](/behavioral/mediator.md) | Connects objects and acts as a proxy | ✘ |
|
||||
| [Memento](/behavioral/memento.md) | Generate an opaque token that can be used to go back to a previous state | ✘ |
|
||||
| [Observer](/behavioral/observer.md) | Provide a callback for notification of events/changes to data | ✔ |
|
||||
| [Registry](/behavioral/registry.md) | Keep track of all subclasses of a given class | ✘ |
|
||||
| [State](/behavioral/state.md) | Encapsulates varying behavior for the same object based on its internal state | ✘ |
|
||||
| [Strategy](/behavioral/strategy.md) | Enables an algorithm's behavior to be selected at runtime | ✔ |
|
||||
| [Template](/behavioral/template.md) | Defines a skeleton class which defers some methods to subclasses | ✘ |
|
||||
| [Visitor](/behavioral/visitor.md) | Separates an algorithm from an object on which it operates | ✘ |
|
||||
|
||||
## Synchronization Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Condition Variable](/synchronization/condition_variable.md) | Provides a mechanism for threads to temporarily give up access in order to wait for some condition | ✘ |
|
||||
| [Lock/Mutex](/synchronization/mutex.md) | Enforces mutual exclusion limit on a resource to gain exclusive access | ✘ |
|
||||
| [Monitor](/synchronization/monitor.md) | Combination of mutex and condition variable patterns | ✘ |
|
||||
| [Read-Write Lock](/synchronization/read_write_lock.md) | Allows parallel read access, but only exclusive access on write operations to a resource | ✘ |
|
||||
| [Semaphore](/synchronization/semaphore.md) | Allows controlling access to a common resource | ✔ |
|
||||
|
||||
## Concurrency Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [N-Barrier](/concurrency/barrier.md) | Prevents a process from proceeding until all N processes reach to the barrier | ✘ |
|
||||
| [Bounded Parallelism](/concurrency/bounded_parallelism.md) | Completes large number of independent tasks with resource limits | ✔ |
|
||||
| [Broadcast](/concurrency/broadcast.md) | Transfers a message to all recipients simultaneously | ✘ |
|
||||
| [Coroutines](/concurrency/coroutine.md) | Subroutines that allow suspending and resuming execution at certain locations | ✘ |
|
||||
| [Generators](/concurrency/generator.md) | Yields a sequence of values one at a time | ✔ |
|
||||
| [Reactor](/concurrency/reactor.md) | Demultiplexes service requests delivered concurrently to a service handler and dispatches them syncronously to the associated request handlers | ✘ |
|
||||
| [Parallelism](/concurrency/parallelism.md) | Completes large number of independent tasks | ✔ |
|
||||
| [Producer Consumer](/concurrency/producer_consumer.md) | Separates tasks from task executions | ✘ |
|
||||
|
||||
## Messaging Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Fan-In](/messaging/fan_in.md) | Funnels tasks to a work sink (e.g. server) | ✔ |
|
||||
| [Fan-Out](/messaging/fan_out.md) | Distributes tasks among workers (e.g. producer) | ✔ |
|
||||
| [Futures & Promises](/messaging/futures_promises.md) | Acts as a place-holder of a result that is initially unknown for synchronization purposes | ✘ |
|
||||
| [Publish/Subscribe](/messaging/publish_subscribe.md) | Passes information to a collection of recipients who subscribed to a topic | ✔ |
|
||||
| [Push & Pull](/messaging/push_pull.md) | Distributes messages to multiple workers, arranged in a pipeline | ✘ |
|
||||
|
||||
## Stability Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Bulkheads](/stability/bulkhead.md) | Enforces a principle of failure containment (i.e. prevents cascading failures) | ✘ |
|
||||
| [Circuit-Breaker](/stability/circuit-breaker.md) | Stops the flow of the requests when requests are likely to fail | ✔ |
|
||||
| [Deadline](/stability/deadline.md) | Allows clients to stop waiting for a response once the probability of response becomes low (e.g. after waiting 10 seconds for a page refresh) | ✘ |
|
||||
| [Fail-Fast](/stability/fail_fast.md) | Checks the availability of required resources at the start of a request and fails if the requirements are not satisfied | ✘ |
|
||||
| [Handshaking](/stability/handshaking.md) | Asks a component if it can take any more load, if it can't, the request is declined | ✘ |
|
||||
| [Steady-State](/stability/steady_state.md) | For every service that accumulates a resource, some other service must recycle that resource | ✘ |
|
||||
|
||||
## Profiling Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Timing Functions](/profiling/timing.md) | Wraps a function and logs the execution | ✔ |
|
||||
|
||||
## Idioms
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Functional Options](/idiom/functional-options.md) | Allows creating clean APIs with sane defaults and idiomatic overrides | ✔ |
|
||||
|
||||
## Anti-Patterns
|
||||
|
||||
| Pattern | Description | Status |
|
||||
|:-------:|:----------- |:------:|
|
||||
| [Cascading Failures](/anti-patterns/cascading_failures.md) | A failure in a system of interconnected parts in which the failure of a part causes a domino effect | ✘ |
|
||||
|
||||
124
SUMMARY.md
124
SUMMARY.md
@ -1,62 +1,62 @@
|
||||
# Summary
|
||||
|
||||
* [Go Patterns](/README.md)
|
||||
* [Creational Patterns](/README.md#creational-patterns)
|
||||
* [Abstract Factory](/creational/abstract_factory.md)
|
||||
* [Builder](/creational/builder.md)
|
||||
* [Factory Method](/creational/factory.md)
|
||||
* [Object Pool](/creational/object-pool.md)
|
||||
* [Singleton](/creational/singleton.md)
|
||||
* [Structural Patterns](/README.md#structural-patterns)
|
||||
* [Bridge](/structural/bridge.md)
|
||||
* [Composite](/structural/composite.md)
|
||||
* [Decorator](/structural/decorator.md)
|
||||
* [Facade](/structural/facade.md)
|
||||
* [Flyweight](/structural/flyweight.md)
|
||||
* [Proxy](/structural/proxy.md)
|
||||
* [Behavioral Patterns](/README.md#behavioral-patterns)
|
||||
* [Chain of Responsibility](/behavioral/chain_of_responsibility.md)
|
||||
* [Command](/behavioral/command.md)
|
||||
* [Mediator](/behavioral/mediator.md)
|
||||
* [Memento](/behavioral/memento.md)
|
||||
* [Observer](/behavioral/observer.md)
|
||||
* [Registry](/behavioral/registry.md)
|
||||
* [State](/behavioral/state.md)
|
||||
* [Strategy](/behavioral/strategy.md)
|
||||
* [Template](/behavioral/template.md)
|
||||
* [Visitor](/behavioral/visitor.md)
|
||||
* [Synchronization Patterns](/README.md#synchronization-patterns)
|
||||
* [Condition Variable](/synchronization/condition_variable.md)
|
||||
* [Lock/Mutex](/synchronization/mutex.md)
|
||||
* [Monitor](/synchronization/monitor.md)
|
||||
* [Read-Write Lock](/synchronization/read_write_lock.md)
|
||||
* [Semaphore](/synchronization/semaphore.md)
|
||||
* [Concurrency Patterns](/README.md#concurrency-patterns)
|
||||
* [N-Barrier](/concurrency/barrier.md)
|
||||
* [Bounded Parallelism](/concurrency/bounded_parallelism.md)
|
||||
* [Broadcast](/concurrency/broadcast.md)
|
||||
* [Coroutines](/concurrency/coroutine.md)
|
||||
* [Generators](/concurrency/generator.md)
|
||||
* [Reactor](/concurrency/reactor.md)
|
||||
* [Parallelism](/concurrency/parallelism.md)
|
||||
* [Producer Consumer](/concurrency/producer_consumer.md)
|
||||
* [Messaging Patterns](/README.md#messaging-patterns)
|
||||
* [Fan-In](/messaging/fan_in.md)
|
||||
* [Fan-Out](/messaging/fan_out.md)
|
||||
* [Futures & Promises](/messaging/futures_promises.md)
|
||||
* [Publish/Subscribe](/messaging/publish_subscribe.md)
|
||||
* [Push & Pull](/messaging/push_pull.md)
|
||||
* [Stability Patterns](/README.md#stability-patterns)
|
||||
* [Bulkheads](/stability/bulkhead.md)
|
||||
* [Circuit-Breaker](/stability/circuit-breaker.md)
|
||||
* [Deadline](/stability/deadline.md)
|
||||
* [Fail-Fast](/stability/fail_fast.md)
|
||||
* [Handshaking](/stability/handshaking.md)
|
||||
* [Steady-State](/stability/steady_state.md)
|
||||
* [Profiling Patterns](/README.md#profiling-patterns)
|
||||
* [Timing Functions](/profiling/timing.md)
|
||||
* [Idioms](/README.md#idioms)
|
||||
* [Functional Options](/idiom/functional-options.md)
|
||||
* [Anti-Patterns](/README.md#anti-patterns)
|
||||
* [Cascading Failures](/anti-patterns/cascading_failures.md)
|
||||
* [Contributing](/CONTRIBUTING.md)
|
||||
# Summary
|
||||
|
||||
* [Go Patterns](/README.md)
|
||||
* [Creational Patterns](/README.md#creational-patterns)
|
||||
* [Abstract Factory](/creational/abstract_factory.md)
|
||||
* [Builder](/creational/builder.md)
|
||||
* [Factory Method](/creational/factory.md)
|
||||
* [Object Pool](/creational/object-pool.md)
|
||||
* [Singleton](/creational/singleton.md)
|
||||
* [Structural Patterns](/README.md#structural-patterns)
|
||||
* [Bridge](/structural/bridge.md)
|
||||
* [Composite](/structural/composite.md)
|
||||
* [Decorator](/structural/decorator.md)
|
||||
* [Facade](/structural/facade.md)
|
||||
* [Flyweight](/structural/flyweight.md)
|
||||
* [Proxy](/structural/proxy.md)
|
||||
* [Behavioral Patterns](/README.md#behavioral-patterns)
|
||||
* [Chain of Responsibility](/behavioral/chain_of_responsibility.md)
|
||||
* [Command](/behavioral/command.md)
|
||||
* [Mediator](/behavioral/mediator.md)
|
||||
* [Memento](/behavioral/memento.md)
|
||||
* [Observer](/behavioral/observer.md)
|
||||
* [Registry](/behavioral/registry.md)
|
||||
* [State](/behavioral/state.md)
|
||||
* [Strategy](/behavioral/strategy.md)
|
||||
* [Template](/behavioral/template.md)
|
||||
* [Visitor](/behavioral/visitor.md)
|
||||
* [Synchronization Patterns](/README.md#synchronization-patterns)
|
||||
* [Condition Variable](/synchronization/condition_variable.md)
|
||||
* [Lock/Mutex](/synchronization/mutex.md)
|
||||
* [Monitor](/synchronization/monitor.md)
|
||||
* [Read-Write Lock](/synchronization/read_write_lock.md)
|
||||
* [Semaphore](/synchronization/semaphore.md)
|
||||
* [Concurrency Patterns](/README.md#concurrency-patterns)
|
||||
* [N-Barrier](/concurrency/barrier.md)
|
||||
* [Bounded Parallelism](/concurrency/bounded_parallelism.md)
|
||||
* [Broadcast](/concurrency/broadcast.md)
|
||||
* [Coroutines](/concurrency/coroutine.md)
|
||||
* [Generators](/concurrency/generator.md)
|
||||
* [Reactor](/concurrency/reactor.md)
|
||||
* [Parallelism](/concurrency/parallelism.md)
|
||||
* [Producer Consumer](/concurrency/producer_consumer.md)
|
||||
* [Messaging Patterns](/README.md#messaging-patterns)
|
||||
* [Fan-In](/messaging/fan_in.md)
|
||||
* [Fan-Out](/messaging/fan_out.md)
|
||||
* [Futures & Promises](/messaging/futures_promises.md)
|
||||
* [Publish/Subscribe](/messaging/publish_subscribe.md)
|
||||
* [Push & Pull](/messaging/push_pull.md)
|
||||
* [Stability Patterns](/README.md#stability-patterns)
|
||||
* [Bulkheads](/stability/bulkhead.md)
|
||||
* [Circuit-Breaker](/stability/circuit-breaker.md)
|
||||
* [Deadline](/stability/deadline.md)
|
||||
* [Fail-Fast](/stability/fail_fast.md)
|
||||
* [Handshaking](/stability/handshaking.md)
|
||||
* [Steady-State](/stability/steady_state.md)
|
||||
* [Profiling Patterns](/README.md#profiling-patterns)
|
||||
* [Timing Functions](/profiling/timing.md)
|
||||
* [Idioms](/README.md#idioms)
|
||||
* [Functional Options](/idiom/functional-options.md)
|
||||
* [Anti-Patterns](/README.md#anti-patterns)
|
||||
* [Cascading Failures](/anti-patterns/cascading_failures.md)
|
||||
* [Contributing](/CONTRIBUTING.md)
|
||||
|
||||
@ -1,47 +1,47 @@
|
||||
# Observer Pattern
|
||||
|
||||
The [observer pattern](https://en.wikipedia.org/wiki/Observer_pattern) allows a type instance to "publish" events to other type instances ("observers") who wish to be updated when a particular event occurs.
|
||||
|
||||
## Implementation
|
||||
|
||||
In long-running applications—such as webservers—instances can keep a collection of observers that will receive notification of triggered events.
|
||||
|
||||
Implementations vary, but interfaces can be used to make standard observers and notifiers:
|
||||
|
||||
```go
|
||||
type (
|
||||
// Event defines an indication of a point-in-time occurrence.
|
||||
Event struct {
|
||||
// Data in this case is a simple int, but the actual
|
||||
// implementation would depend on the application.
|
||||
Data int64
|
||||
}
|
||||
|
||||
// Observer defines a standard interface for instances that wish to list for
|
||||
// the occurrence of a specific event.
|
||||
Observer interface {
|
||||
// OnNotify allows an event to be "published" to interface implementations.
|
||||
// In the "real world", error handling would likely be implemented.
|
||||
OnNotify(Event)
|
||||
}
|
||||
|
||||
// Notifier is the instance being observed. Publisher is perhaps another decent
|
||||
// name, but naming things is hard.
|
||||
Notifier interface {
|
||||
// Register allows an instance to register itself to listen/observe
|
||||
// events.
|
||||
Register(Observer)
|
||||
// Deregister allows an instance to remove itself from the collection
|
||||
// of observers/listeners.
|
||||
Deregister(Observer)
|
||||
// Notify publishes new events to listeners. The method is not
|
||||
// absolutely necessary, as each implementation could define this itself
|
||||
// without losing functionality.
|
||||
Notify(Event)
|
||||
}
|
||||
)
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
For usage, see [observer/main.go](observer/main.go) or [view in the Playground](https://play.golang.org/p/cr8jEmDmw0).
|
||||
# Observer Pattern
|
||||
|
||||
The [observer pattern](https://en.wikipedia.org/wiki/Observer_pattern) allows a type instance to "publish" events to other type instances ("observers") who wish to be updated when a particular event occurs.
|
||||
|
||||
## Implementation
|
||||
|
||||
In long-running applications—such as webservers—instances can keep a collection of observers that will receive notification of triggered events.
|
||||
|
||||
Implementations vary, but interfaces can be used to make standard observers and notifiers:
|
||||
|
||||
```go
|
||||
type (
|
||||
// Event defines an indication of a point-in-time occurrence.
|
||||
Event struct {
|
||||
// Data in this case is a simple int, but the actual
|
||||
// implementation would depend on the application.
|
||||
Data int64
|
||||
}
|
||||
|
||||
// Observer defines a standard interface for instances that wish to list for
|
||||
// the occurrence of a specific event.
|
||||
Observer interface {
|
||||
// OnNotify allows an event to be "published" to interface implementations.
|
||||
// In the "real world", error handling would likely be implemented.
|
||||
OnNotify(Event)
|
||||
}
|
||||
|
||||
// Notifier is the instance being observed. Publisher is perhaps another decent
|
||||
// name, but naming things is hard.
|
||||
Notifier interface {
|
||||
// Register allows an instance to register itself to listen/observe
|
||||
// events.
|
||||
Register(Observer)
|
||||
// Deregister allows an instance to remove itself from the collection
|
||||
// of observers/listeners.
|
||||
Deregister(Observer)
|
||||
// Notify publishes new events to listeners. The method is not
|
||||
// absolutely necessary, as each implementation could define this itself
|
||||
// without losing functionality.
|
||||
Notify(Event)
|
||||
}
|
||||
)
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
For usage, see [observer/main.go](observer/main.go) or [view in the Playground](https://play.golang.org/p/cr8jEmDmw0).
|
||||
|
||||
@ -1,93 +1,93 @@
|
||||
// Package main serves as an example application that makes use of the observer pattern.
|
||||
// Playground: https://play.golang.org/p/cr8jEmDmw0
|
||||
package main
|
||||
|
||||
import (
|
||||
"fmt"
|
||||
"time"
|
||||
)
|
||||
|
||||
type (
|
||||
// Event defines an indication of a point-in-time occurrence.
|
||||
Event struct {
|
||||
// Data in this case is a simple int, but the actual
|
||||
// implementation would depend on the application.
|
||||
Data int64
|
||||
}
|
||||
|
||||
// Observer defines a standard interface for instances that wish to list for
|
||||
// the occurrence of a specific event.
|
||||
Observer interface {
|
||||
// OnNotify allows an event to be "published" to interface implementations.
|
||||
// In the "real world", error handling would likely be implemented.
|
||||
OnNotify(Event)
|
||||
}
|
||||
|
||||
// Notifier is the instance being observed. Publisher is perhaps another decent
|
||||
// name, but naming things is hard.
|
||||
Notifier interface {
|
||||
// Register allows an instance to register itself to listen/observe
|
||||
// events.
|
||||
Register(Observer)
|
||||
// Deregister allows an instance to remove itself from the collection
|
||||
// of observers/listeners.
|
||||
Deregister(Observer)
|
||||
// Notify publishes new events to listeners. The method is not
|
||||
// absolutely necessary, as each implementation could define this itself
|
||||
// without losing functionality.
|
||||
Notify(Event)
|
||||
}
|
||||
)
|
||||
|
||||
type (
|
||||
eventObserver struct{
|
||||
id int
|
||||
}
|
||||
|
||||
eventNotifier struct{
|
||||
// Using a map with an empty struct allows us to keep the observers
|
||||
// unique while still keeping memory usage relatively low.
|
||||
observers map[Observer]struct{}
|
||||
}
|
||||
)
|
||||
|
||||
func (o *eventObserver) OnNotify(e Event) {
|
||||
fmt.Printf("*** Observer %d received: %d\n", o.id, e.Data)
|
||||
}
|
||||
|
||||
func (o *eventNotifier) Register(l Observer) {
|
||||
o.observers[l] = struct{}{}
|
||||
}
|
||||
|
||||
func (o *eventNotifier) Deregister(l Observer) {
|
||||
delete(o.observers, l)
|
||||
}
|
||||
|
||||
func (p *eventNotifier) Notify(e Event) {
|
||||
for o := range p.observers {
|
||||
o.OnNotify(e)
|
||||
}
|
||||
}
|
||||
|
||||
func main() {
|
||||
// Initialize a new Notifier.
|
||||
n := eventNotifier{
|
||||
observers: map[Observer]struct{}{},
|
||||
}
|
||||
|
||||
// Register a couple of observers.
|
||||
n.Register(&eventObserver{id: 1})
|
||||
n.Register(&eventObserver{id: 2})
|
||||
|
||||
// A simple loop publishing the current Unix timestamp to observers.
|
||||
stop := time.NewTimer(10 * time.Second).C
|
||||
tick := time.NewTicker(time.Second).C
|
||||
for {
|
||||
select {
|
||||
case <- stop:
|
||||
return
|
||||
case t := <-tick:
|
||||
n.Notify(Event{Data: t.UnixNano()})
|
||||
}
|
||||
}
|
||||
// Package main serves as an example application that makes use of the observer pattern.
|
||||
// Playground: https://play.golang.org/p/cr8jEmDmw0
|
||||
package main
|
||||
|
||||
import (
|
||||
"fmt"
|
||||
"time"
|
||||
)
|
||||
|
||||
type (
|
||||
// Event defines an indication of a point-in-time occurrence.
|
||||
Event struct {
|
||||
// Data in this case is a simple int, but the actual
|
||||
// implementation would depend on the application.
|
||||
Data int64
|
||||
}
|
||||
|
||||
// Observer defines a standard interface for instances that wish to list for
|
||||
// the occurrence of a specific event.
|
||||
Observer interface {
|
||||
// OnNotify allows an event to be "published" to interface implementations.
|
||||
// In the "real world", error handling would likely be implemented.
|
||||
OnNotify(Event)
|
||||
}
|
||||
|
||||
// Notifier is the instance being observed. Publisher is perhaps another decent
|
||||
// name, but naming things is hard.
|
||||
Notifier interface {
|
||||
// Register allows an instance to register itself to listen/observe
|
||||
// events.
|
||||
Register(Observer)
|
||||
// Deregister allows an instance to remove itself from the collection
|
||||
// of observers/listeners.
|
||||
Deregister(Observer)
|
||||
// Notify publishes new events to listeners. The method is not
|
||||
// absolutely necessary, as each implementation could define this itself
|
||||
// without losing functionality.
|
||||
Notify(Event)
|
||||
}
|
||||
)
|
||||
|
||||
type (
|
||||
eventObserver struct{
|
||||
id int
|
||||
}
|
||||
|
||||
eventNotifier struct{
|
||||
// Using a map with an empty struct allows us to keep the observers
|
||||
// unique while still keeping memory usage relatively low.
|
||||
observers map[Observer]struct{}
|
||||
}
|
||||
)
|
||||
|
||||
func (o *eventObserver) OnNotify(e Event) {
|
||||
fmt.Printf("*** Observer %d received: %d\n", o.id, e.Data)
|
||||
}
|
||||
|
||||
func (o *eventNotifier) Register(l Observer) {
|
||||
o.observers[l] = struct{}{}
|
||||
}
|
||||
|
||||
func (o *eventNotifier) Deregister(l Observer) {
|
||||
delete(o.observers, l)
|
||||
}
|
||||
|
||||
func (p *eventNotifier) Notify(e Event) {
|
||||
for o := range p.observers {
|
||||
o.OnNotify(e)
|
||||
}
|
||||
}
|
||||
|
||||
func main() {
|
||||
// Initialize a new Notifier.
|
||||
n := eventNotifier{
|
||||
observers: map[Observer]struct{}{},
|
||||
}
|
||||
|
||||
// Register a couple of observers.
|
||||
n.Register(&eventObserver{id: 1})
|
||||
n.Register(&eventObserver{id: 2})
|
||||
|
||||
// A simple loop publishing the current Unix timestamp to observers.
|
||||
stop := time.NewTimer(10 * time.Second).C
|
||||
tick := time.NewTicker(time.Second).C
|
||||
for {
|
||||
select {
|
||||
case <- stop:
|
||||
return
|
||||
case t := <-tick:
|
||||
n.Notify(Event{Data: t.UnixNano()})
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -1,55 +1,55 @@
|
||||
# Strategy Pattern
|
||||
Strategy behavioral design pattern enables an algorithm's behavior to be selected at runtime.
|
||||
|
||||
It defines algorithms, encapsulates them, and uses them interchangeably.
|
||||
|
||||
## Implementation
|
||||
Implementation of an interchangeable operator object that operates on integers.
|
||||
|
||||
```go
|
||||
type Operator interface {
|
||||
Apply(int, int) int
|
||||
}
|
||||
|
||||
type Operation struct {
|
||||
Operator Operator
|
||||
}
|
||||
|
||||
func (o *Operation) Operate(leftValue, rightValue int) int {
|
||||
return o.Operator.Apply(leftValue, rightValue)
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
### Addition Operator
|
||||
```go
|
||||
type Addition struct{}
|
||||
|
||||
func (Addition) Apply(lval, rval int) int {
|
||||
return lval + rval
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
add := Operation{Addition{}}
|
||||
add.Operate(3, 5) // 8
|
||||
```
|
||||
|
||||
### Multiplication Operator
|
||||
```go
|
||||
type Multiplication struct{}
|
||||
|
||||
func (Multiplication) Apply(lval, rval int) int {
|
||||
return lval * rval
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
mult := Operation{Multiplication{}}
|
||||
|
||||
mult.Operate(3, 5) // 15
|
||||
```
|
||||
|
||||
## Rules of Thumb
|
||||
- Strategy pattern is similar to Template pattern except in its granularity.
|
||||
- Strategy pattern lets you change the guts of an object. Decorator pattern lets you change the skin.
|
||||
# Strategy Pattern
|
||||
Strategy behavioral design pattern enables an algorithm's behavior to be selected at runtime.
|
||||
|
||||
It defines algorithms, encapsulates them, and uses them interchangeably.
|
||||
|
||||
## Implementation
|
||||
Implementation of an interchangeable operator object that operates on integers.
|
||||
|
||||
```go
|
||||
type Operator interface {
|
||||
Apply(int, int) int
|
||||
}
|
||||
|
||||
type Operation struct {
|
||||
Operator Operator
|
||||
}
|
||||
|
||||
func (o *Operation) Operate(leftValue, rightValue int) int {
|
||||
return o.Operator.Apply(leftValue, rightValue)
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
### Addition Operator
|
||||
```go
|
||||
type Addition struct{}
|
||||
|
||||
func (Addition) Apply(lval, rval int) int {
|
||||
return lval + rval
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
add := Operation{Addition{}}
|
||||
add.Operate(3, 5) // 8
|
||||
```
|
||||
|
||||
### Multiplication Operator
|
||||
```go
|
||||
type Multiplication struct{}
|
||||
|
||||
func (Multiplication) Apply(lval, rval int) int {
|
||||
return lval * rval
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
mult := Operation{Multiplication{}}
|
||||
|
||||
mult.Operate(3, 5) // 15
|
||||
```
|
||||
|
||||
## Rules of Thumb
|
||||
- Strategy pattern is similar to Template pattern except in its granularity.
|
||||
- Strategy pattern lets you change the guts of an object. Decorator pattern lets you change the skin.
|
||||
|
||||
34
book.json
34
book.json
@ -1,17 +1,17 @@
|
||||
{
|
||||
"plugins": [
|
||||
"-search",
|
||||
"-lunr",
|
||||
"github",
|
||||
"edit-link"
|
||||
],
|
||||
"pluginsConfig": {
|
||||
"github": {
|
||||
"url": "https://github.com/tmrts/go-patterns"
|
||||
},
|
||||
"edit-link": {
|
||||
"base": "https://github.com/tmrts/go-patterns/edit/master/",
|
||||
"label": ""
|
||||
}
|
||||
}
|
||||
}
|
||||
{
|
||||
"plugins": [
|
||||
"-search",
|
||||
"-lunr",
|
||||
"github",
|
||||
"edit-link"
|
||||
],
|
||||
"pluginsConfig": {
|
||||
"github": {
|
||||
"url": "https://github.com/tmrts/go-patterns"
|
||||
},
|
||||
"edit-link": {
|
||||
"base": "https://github.com/tmrts/go-patterns/edit/master/",
|
||||
"label": ""
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
@ -1,121 +1,121 @@
|
||||
package bounded_parallelism
|
||||
|
||||
import (
|
||||
"crypto/md5"
|
||||
"errors"
|
||||
"fmt"
|
||||
"io/ioutil"
|
||||
"os"
|
||||
"path/filepath"
|
||||
"sort"
|
||||
"sync"
|
||||
)
|
||||
|
||||
// walkFiles starts a goroutine to walk the directory tree at root and send the
|
||||
// path of each regular file on the string channel. It sends the result of the
|
||||
// walk on the error channel. If done is closed, walkFiles abandons its work.
|
||||
func walkFiles(done <-chan struct{}, root string) (<-chan string, <-chan error) {
|
||||
paths := make(chan string)
|
||||
errc := make(chan error, 1)
|
||||
go func() { // HL
|
||||
// Close the paths channel after Walk returns.
|
||||
defer close(paths) // HL
|
||||
// No select needed for this send, since errc is buffered.
|
||||
errc <- filepath.Walk(root, func(path string, info os.FileInfo, err error) error { // HL
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
if !info.Mode().IsRegular() {
|
||||
return nil
|
||||
}
|
||||
select {
|
||||
case paths <- path: // HL
|
||||
case <-done: // HL
|
||||
return errors.New("walk canceled")
|
||||
}
|
||||
return nil
|
||||
})
|
||||
}()
|
||||
return paths, errc
|
||||
}
|
||||
|
||||
// A result is the product of reading and summing a file using MD5.
|
||||
type result struct {
|
||||
path string
|
||||
sum [md5.Size]byte
|
||||
err error
|
||||
}
|
||||
|
||||
// digester reads path names from paths and sends digests of the corresponding
|
||||
// files on c until either paths or done is closed.
|
||||
func digester(done <-chan struct{}, paths <-chan string, c chan<- result) {
|
||||
for path := range paths { // HLpaths
|
||||
data, err := ioutil.ReadFile(path)
|
||||
select {
|
||||
case c <- result{path, md5.Sum(data), err}:
|
||||
case <-done:
|
||||
return
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// MD5All reads all the files in the file tree rooted at root and returns a map
|
||||
// from file path to the MD5 sum of the file's contents. If the directory walk
|
||||
// fails or any read operation fails, MD5All returns an error. In that case,
|
||||
// MD5All does not wait for inflight read operations to complete.
|
||||
func MD5All(root string) (map[string][md5.Size]byte, error) {
|
||||
// MD5All closes the done channel when it returns; it may do so before
|
||||
// receiving all the values from c and errc.
|
||||
done := make(chan struct{})
|
||||
defer close(done)
|
||||
|
||||
paths, errc := walkFiles(done, root)
|
||||
|
||||
// Start a fixed number of goroutines to read and digest files.
|
||||
c := make(chan result) // HLc
|
||||
var wg sync.WaitGroup
|
||||
const numDigesters = 20
|
||||
wg.Add(numDigesters)
|
||||
for i := 0; i < numDigesters; i++ {
|
||||
go func() {
|
||||
digester(done, paths, c) // HLc
|
||||
wg.Done()
|
||||
}()
|
||||
}
|
||||
go func() {
|
||||
wg.Wait()
|
||||
close(c) // HLc
|
||||
}()
|
||||
// End of pipeline. OMIT
|
||||
|
||||
m := make(map[string][md5.Size]byte)
|
||||
for r := range c {
|
||||
if r.err != nil {
|
||||
return nil, r.err
|
||||
}
|
||||
m[r.path] = r.sum
|
||||
}
|
||||
// Check whether the Walk failed.
|
||||
if err := <-errc; err != nil { // HLerrc
|
||||
return nil, err
|
||||
}
|
||||
return m, nil
|
||||
}
|
||||
|
||||
func main() {
|
||||
// Calculate the MD5 sum of all files under the specified directory,
|
||||
// then print the results sorted by path name.
|
||||
m, err := MD5All(os.Args[1])
|
||||
if err != nil {
|
||||
fmt.Println(err)
|
||||
return
|
||||
}
|
||||
var paths []string
|
||||
for path := range m {
|
||||
paths = append(paths, path)
|
||||
}
|
||||
sort.Strings(paths)
|
||||
for _, path := range paths {
|
||||
fmt.Printf("%x %s\n", m[path], path)
|
||||
}
|
||||
}
|
||||
package bounded_parallelism
|
||||
|
||||
import (
|
||||
"crypto/md5"
|
||||
"errors"
|
||||
"fmt"
|
||||
"io/ioutil"
|
||||
"os"
|
||||
"path/filepath"
|
||||
"sort"
|
||||
"sync"
|
||||
)
|
||||
|
||||
// walkFiles starts a goroutine to walk the directory tree at root and send the
|
||||
// path of each regular file on the string channel. It sends the result of the
|
||||
// walk on the error channel. If done is closed, walkFiles abandons its work.
|
||||
func walkFiles(done <-chan struct{}, root string) (<-chan string, <-chan error) {
|
||||
paths := make(chan string)
|
||||
errc := make(chan error, 1)
|
||||
go func() { // HL
|
||||
// Close the paths channel after Walk returns.
|
||||
defer close(paths) // HL
|
||||
// No select needed for this send, since errc is buffered.
|
||||
errc <- filepath.Walk(root, func(path string, info os.FileInfo, err error) error { // HL
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
if !info.Mode().IsRegular() {
|
||||
return nil
|
||||
}
|
||||
select {
|
||||
case paths <- path: // HL
|
||||
case <-done: // HL
|
||||
return errors.New("walk canceled")
|
||||
}
|
||||
return nil
|
||||
})
|
||||
}()
|
||||
return paths, errc
|
||||
}
|
||||
|
||||
// A result is the product of reading and summing a file using MD5.
|
||||
type result struct {
|
||||
path string
|
||||
sum [md5.Size]byte
|
||||
err error
|
||||
}
|
||||
|
||||
// digester reads path names from paths and sends digests of the corresponding
|
||||
// files on c until either paths or done is closed.
|
||||
func digester(done <-chan struct{}, paths <-chan string, c chan<- result) {
|
||||
for path := range paths { // HLpaths
|
||||
data, err := ioutil.ReadFile(path)
|
||||
select {
|
||||
case c <- result{path, md5.Sum(data), err}:
|
||||
case <-done:
|
||||
return
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// MD5All reads all the files in the file tree rooted at root and returns a map
|
||||
// from file path to the MD5 sum of the file's contents. If the directory walk
|
||||
// fails or any read operation fails, MD5All returns an error. In that case,
|
||||
// MD5All does not wait for inflight read operations to complete.
|
||||
func MD5All(root string) (map[string][md5.Size]byte, error) {
|
||||
// MD5All closes the done channel when it returns; it may do so before
|
||||
// receiving all the values from c and errc.
|
||||
done := make(chan struct{})
|
||||
defer close(done)
|
||||
|
||||
paths, errc := walkFiles(done, root)
|
||||
|
||||
// Start a fixed number of goroutines to read and digest files.
|
||||
c := make(chan result) // HLc
|
||||
var wg sync.WaitGroup
|
||||
const numDigesters = 20
|
||||
wg.Add(numDigesters)
|
||||
for i := 0; i < numDigesters; i++ {
|
||||
go func() {
|
||||
digester(done, paths, c) // HLc
|
||||
wg.Done()
|
||||
}()
|
||||
}
|
||||
go func() {
|
||||
wg.Wait()
|
||||
close(c) // HLc
|
||||
}()
|
||||
// End of pipeline. OMIT
|
||||
|
||||
m := make(map[string][md5.Size]byte)
|
||||
for r := range c {
|
||||
if r.err != nil {
|
||||
return nil, r.err
|
||||
}
|
||||
m[r.path] = r.sum
|
||||
}
|
||||
// Check whether the Walk failed.
|
||||
if err := <-errc; err != nil { // HLerrc
|
||||
return nil, err
|
||||
}
|
||||
return m, nil
|
||||
}
|
||||
|
||||
func main() {
|
||||
// Calculate the MD5 sum of all files under the specified directory,
|
||||
// then print the results sorted by path name.
|
||||
m, err := MD5All(os.Args[1])
|
||||
if err != nil {
|
||||
fmt.Println(err)
|
||||
return
|
||||
}
|
||||
var paths []string
|
||||
for path := range m {
|
||||
paths = append(paths, path)
|
||||
}
|
||||
sort.Strings(paths)
|
||||
for _, path := range paths {
|
||||
fmt.Printf("%x %s\n", m[path], path)
|
||||
}
|
||||
}
|
||||
|
||||
@ -1,7 +1,7 @@
|
||||
# Bounded Parallelism Pattern
|
||||
|
||||
[Bounded parallelism](https://blog.golang.org/pipelines#TOC_9.) is similar to [parallelism](parallelism.md), but allows limits to be placed on allocation.
|
||||
|
||||
# Implementation and Example
|
||||
|
||||
# Bounded Parallelism Pattern
|
||||
|
||||
[Bounded parallelism](https://blog.golang.org/pipelines#TOC_9.) is similar to [parallelism](parallelism.md), but allows limits to be placed on allocation.
|
||||
|
||||
# Implementation and Example
|
||||
|
||||
An example showing implementation and usage can be found in [bounded_parallelism.go](bounded_parallelism.go).
|
||||
@ -1,38 +1,38 @@
|
||||
# Generator Pattern
|
||||
|
||||
[Generators](https://en.wikipedia.org/wiki/Generator_(computer_programming)) yields a sequence of values one at a time.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
func Count(start int, end int) chan int {
|
||||
ch := make(chan int)
|
||||
|
||||
go func(ch chan int) {
|
||||
for i := start; i <= end ; i++ {
|
||||
// Blocks on the operation
|
||||
ch <- i
|
||||
}
|
||||
|
||||
close(ch)
|
||||
}(ch)
|
||||
|
||||
return ch
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
fmt.Println("No bottles of beer on the wall")
|
||||
|
||||
for i := range Count(1, 99) {
|
||||
fmt.Println("Pass it around, put one up,", i, "bottles of beer on the wall")
|
||||
// Pass it around, put one up, 1 bottles of beer on the wall
|
||||
// Pass it around, put one up, 2 bottles of beer on the wall
|
||||
// ...
|
||||
// Pass it around, put one up, 99 bottles of beer on the wall
|
||||
}
|
||||
|
||||
fmt.Println(100, "bottles of beer on the wall")
|
||||
```
|
||||
# Generator Pattern
|
||||
|
||||
[Generators](https://en.wikipedia.org/wiki/Generator_(computer_programming)) yields a sequence of values one at a time.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
func Count(start int, end int) chan int {
|
||||
ch := make(chan int)
|
||||
|
||||
go func(ch chan int) {
|
||||
for i := start; i <= end ; i++ {
|
||||
// Blocks on the operation
|
||||
ch <- i
|
||||
}
|
||||
|
||||
close(ch)
|
||||
}(ch)
|
||||
|
||||
return ch
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
fmt.Println("No bottles of beer on the wall")
|
||||
|
||||
for i := range Count(1, 99) {
|
||||
fmt.Println("Pass it around, put one up,", i, "bottles of beer on the wall")
|
||||
// Pass it around, put one up, 1 bottles of beer on the wall
|
||||
// Pass it around, put one up, 2 bottles of beer on the wall
|
||||
// ...
|
||||
// Pass it around, put one up, 99 bottles of beer on the wall
|
||||
}
|
||||
|
||||
fmt.Println(100, "bottles of beer on the wall")
|
||||
```
|
||||
|
||||
@ -1,109 +1,109 @@
|
||||
package parallelism
|
||||
|
||||
import (
|
||||
"crypto/md5"
|
||||
"errors"
|
||||
"fmt"
|
||||
"io/ioutil"
|
||||
"os"
|
||||
"path/filepath"
|
||||
"sort"
|
||||
"sync"
|
||||
)
|
||||
|
||||
// A result is the product of reading and summing a file using MD5.
|
||||
type result struct {
|
||||
path string
|
||||
sum [md5.Size]byte
|
||||
err error
|
||||
}
|
||||
|
||||
// sumFiles starts goroutines to walk the directory tree at root and digest each
|
||||
// regular file. These goroutines send the results of the digests on the result
|
||||
// channel and send the result of the walk on the error channel. If done is
|
||||
// closed, sumFiles abandons its work.
|
||||
func sumFiles(done <-chan struct{}, root string) (<-chan result, <-chan error) {
|
||||
// For each regular file, start a goroutine that sums the file and sends
|
||||
// the result on c. Send the result of the walk on errc.
|
||||
c := make(chan result)
|
||||
errc := make(chan error, 1)
|
||||
go func() { // HL
|
||||
var wg sync.WaitGroup
|
||||
err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
if !info.Mode().IsRegular() {
|
||||
return nil
|
||||
}
|
||||
wg.Add(1)
|
||||
go func() { // HL
|
||||
data, err := ioutil.ReadFile(path)
|
||||
select {
|
||||
case c <- result{path, md5.Sum(data), err}: // HL
|
||||
case <-done: // HL
|
||||
}
|
||||
wg.Done()
|
||||
}()
|
||||
// Abort the walk if done is closed.
|
||||
select {
|
||||
case <-done: // HL
|
||||
return errors.New("walk canceled")
|
||||
default:
|
||||
return nil
|
||||
}
|
||||
})
|
||||
// Walk has returned, so all calls to wg.Add are done. Start a
|
||||
// goroutine to close c once all the sends are done.
|
||||
go func() { // HL
|
||||
wg.Wait()
|
||||
close(c) // HL
|
||||
}()
|
||||
// No select needed here, since errc is buffered.
|
||||
errc <- err // HL
|
||||
}()
|
||||
return c, errc
|
||||
}
|
||||
|
||||
// MD5All reads all the files in the file tree rooted at root and returns a map
|
||||
// from file path to the MD5 sum of the file's contents. If the directory walk
|
||||
// fails or any read operation fails, MD5All returns an error. In that case,
|
||||
// MD5All does not wait for inflight read operations to complete.
|
||||
func MD5All(root string) (map[string][md5.Size]byte, error) {
|
||||
// MD5All closes the done channel when it returns; it may do so before
|
||||
// receiving all the values from c and errc.
|
||||
done := make(chan struct{}) // HLdone
|
||||
defer close(done) // HLdone
|
||||
|
||||
c, errc := sumFiles(done, root) // HLdone
|
||||
|
||||
m := make(map[string][md5.Size]byte)
|
||||
for r := range c { // HLrange
|
||||
if r.err != nil {
|
||||
return nil, r.err
|
||||
}
|
||||
m[r.path] = r.sum
|
||||
}
|
||||
if err := <-errc; err != nil {
|
||||
return nil, err
|
||||
}
|
||||
return m, nil
|
||||
}
|
||||
|
||||
func main() {
|
||||
// Calculate the MD5 sum of all files under the specified directory,
|
||||
// then print the results sorted by path name.
|
||||
m, err := MD5All(os.Args[1])
|
||||
if err != nil {
|
||||
fmt.Println(err)
|
||||
return
|
||||
}
|
||||
var paths []string
|
||||
for path := range m {
|
||||
paths = append(paths, path)
|
||||
}
|
||||
sort.Strings(paths)
|
||||
for _, path := range paths {
|
||||
fmt.Printf("%x %s\n", m[path], path)
|
||||
}
|
||||
}
|
||||
package parallelism
|
||||
|
||||
import (
|
||||
"crypto/md5"
|
||||
"errors"
|
||||
"fmt"
|
||||
"io/ioutil"
|
||||
"os"
|
||||
"path/filepath"
|
||||
"sort"
|
||||
"sync"
|
||||
)
|
||||
|
||||
// A result is the product of reading and summing a file using MD5.
|
||||
type result struct {
|
||||
path string
|
||||
sum [md5.Size]byte
|
||||
err error
|
||||
}
|
||||
|
||||
// sumFiles starts goroutines to walk the directory tree at root and digest each
|
||||
// regular file. These goroutines send the results of the digests on the result
|
||||
// channel and send the result of the walk on the error channel. If done is
|
||||
// closed, sumFiles abandons its work.
|
||||
func sumFiles(done <-chan struct{}, root string) (<-chan result, <-chan error) {
|
||||
// For each regular file, start a goroutine that sums the file and sends
|
||||
// the result on c. Send the result of the walk on errc.
|
||||
c := make(chan result)
|
||||
errc := make(chan error, 1)
|
||||
go func() { // HL
|
||||
var wg sync.WaitGroup
|
||||
err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
if !info.Mode().IsRegular() {
|
||||
return nil
|
||||
}
|
||||
wg.Add(1)
|
||||
go func() { // HL
|
||||
data, err := ioutil.ReadFile(path)
|
||||
select {
|
||||
case c <- result{path, md5.Sum(data), err}: // HL
|
||||
case <-done: // HL
|
||||
}
|
||||
wg.Done()
|
||||
}()
|
||||
// Abort the walk if done is closed.
|
||||
select {
|
||||
case <-done: // HL
|
||||
return errors.New("walk canceled")
|
||||
default:
|
||||
return nil
|
||||
}
|
||||
})
|
||||
// Walk has returned, so all calls to wg.Add are done. Start a
|
||||
// goroutine to close c once all the sends are done.
|
||||
go func() { // HL
|
||||
wg.Wait()
|
||||
close(c) // HL
|
||||
}()
|
||||
// No select needed here, since errc is buffered.
|
||||
errc <- err // HL
|
||||
}()
|
||||
return c, errc
|
||||
}
|
||||
|
||||
// MD5All reads all the files in the file tree rooted at root and returns a map
|
||||
// from file path to the MD5 sum of the file's contents. If the directory walk
|
||||
// fails or any read operation fails, MD5All returns an error. In that case,
|
||||
// MD5All does not wait for inflight read operations to complete.
|
||||
func MD5All(root string) (map[string][md5.Size]byte, error) {
|
||||
// MD5All closes the done channel when it returns; it may do so before
|
||||
// receiving all the values from c and errc.
|
||||
done := make(chan struct{}) // HLdone
|
||||
defer close(done) // HLdone
|
||||
|
||||
c, errc := sumFiles(done, root) // HLdone
|
||||
|
||||
m := make(map[string][md5.Size]byte)
|
||||
for r := range c { // HLrange
|
||||
if r.err != nil {
|
||||
return nil, r.err
|
||||
}
|
||||
m[r.path] = r.sum
|
||||
}
|
||||
if err := <-errc; err != nil {
|
||||
return nil, err
|
||||
}
|
||||
return m, nil
|
||||
}
|
||||
|
||||
func main() {
|
||||
// Calculate the MD5 sum of all files under the specified directory,
|
||||
// then print the results sorted by path name.
|
||||
m, err := MD5All(os.Args[1])
|
||||
if err != nil {
|
||||
fmt.Println(err)
|
||||
return
|
||||
}
|
||||
var paths []string
|
||||
for path := range m {
|
||||
paths = append(paths, path)
|
||||
}
|
||||
sort.Strings(paths)
|
||||
for _, path := range paths {
|
||||
fmt.Printf("%x %s\n", m[path], path)
|
||||
}
|
||||
}
|
||||
|
||||
@ -1,7 +1,7 @@
|
||||
# Parallelism Pattern
|
||||
|
||||
[Parallelism](https://blog.golang.org/pipelines#TOC_8.) allows multiple "jobs" or tasks to be run concurrently and asynchronously.
|
||||
|
||||
# Implementation and Example
|
||||
|
||||
# Parallelism Pattern
|
||||
|
||||
[Parallelism](https://blog.golang.org/pipelines#TOC_8.) allows multiple "jobs" or tasks to be run concurrently and asynchronously.
|
||||
|
||||
# Implementation and Example
|
||||
|
||||
An example showing implementation and usage can be found in [parallelism.go](parallelism.go).
|
||||
@ -1,61 +1,61 @@
|
||||
# Builder Pattern
|
||||
|
||||
Builder pattern separates the construction of a complex object from its
|
||||
representation so that the same construction process can create different
|
||||
representations.
|
||||
|
||||
In Go, normally a configuration struct is used to achieve the same behavior,
|
||||
however passing a struct to the builder method fills the code with boilerplate
|
||||
`if cfg.Field != nil {...}` checks.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package car
|
||||
|
||||
type Speed float64
|
||||
|
||||
const (
|
||||
MPH Speed = 1
|
||||
KPH = 1.60934
|
||||
)
|
||||
|
||||
type Color string
|
||||
|
||||
const (
|
||||
BlueColor Color = "blue"
|
||||
GreenColor = "green"
|
||||
RedColor = "red"
|
||||
)
|
||||
|
||||
type Wheels string
|
||||
|
||||
const (
|
||||
SportsWheels Wheels = "sports"
|
||||
SteelWheels = "steel"
|
||||
)
|
||||
|
||||
type Builder interface {
|
||||
Color(Color) Builder
|
||||
Wheels(Wheels) Builder
|
||||
TopSpeed(Speed) Builder
|
||||
Build() Interface
|
||||
}
|
||||
|
||||
type Interface interface {
|
||||
Drive() error
|
||||
Stop() error
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
assembly := car.NewBuilder().Paint(car.RedColor)
|
||||
|
||||
familyCar := assembly.Wheels(car.SportsWheels).TopSpeed(50 * car.MPH).Build()
|
||||
familyCar.Drive()
|
||||
|
||||
sportsCar := assembly.Wheels(car.SteelWheels).TopSpeed(150 * car.MPH).Build()
|
||||
sportsCar.Drive()
|
||||
```
|
||||
# Builder Pattern
|
||||
|
||||
Builder pattern separates the construction of a complex object from its
|
||||
representation so that the same construction process can create different
|
||||
representations.
|
||||
|
||||
In Go, normally a configuration struct is used to achieve the same behavior,
|
||||
however passing a struct to the builder method fills the code with boilerplate
|
||||
`if cfg.Field != nil {...}` checks.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package car
|
||||
|
||||
type Speed float64
|
||||
|
||||
const (
|
||||
MPH Speed = 1
|
||||
KPH = 1.60934
|
||||
)
|
||||
|
||||
type Color string
|
||||
|
||||
const (
|
||||
BlueColor Color = "blue"
|
||||
GreenColor = "green"
|
||||
RedColor = "red"
|
||||
)
|
||||
|
||||
type Wheels string
|
||||
|
||||
const (
|
||||
SportsWheels Wheels = "sports"
|
||||
SteelWheels = "steel"
|
||||
)
|
||||
|
||||
type Builder interface {
|
||||
Color(Color) Builder
|
||||
Wheels(Wheels) Builder
|
||||
TopSpeed(Speed) Builder
|
||||
Build() Interface
|
||||
}
|
||||
|
||||
type Interface interface {
|
||||
Drive() error
|
||||
Stop() error
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
assembly := car.NewBuilder().Paint(car.RedColor)
|
||||
|
||||
familyCar := assembly.Wheels(car.SportsWheels).TopSpeed(50 * car.MPH).Build()
|
||||
familyCar.Drive()
|
||||
|
||||
sportsCar := assembly.Wheels(car.SteelWheels).TopSpeed(150 * car.MPH).Build()
|
||||
sportsCar.Drive()
|
||||
```
|
||||
|
||||
11
creational/factory.go
Normal file
11
creational/factory.go
Normal file
@ -0,0 +1,11 @@
|
||||
package creational
|
||||
|
||||
import "io"
|
||||
|
||||
// 工厂方法创建设计模式允许创建对象，而不必指定将要创建的对象的确切类型。
|
||||
// 示例实现展示了如何使用不同的后端，如内存、磁盘存储。
|
||||
|
||||
// Store 对象类型
|
||||
type Store interface {
|
||||
Open(string) (io.ReadWriteCloser, error)
|
||||
}
|
||||
@ -1,58 +1,65 @@
|
||||
# Factory Method Pattern
|
||||
|
||||
Factory method creational design pattern allows creating objects without having
|
||||
to specify the exact type of the object that will be created.
|
||||
|
||||
## Implementation
|
||||
|
||||
The example implementation shows how to provide a data store with different
|
||||
backends such as in-memory, disk storage.
|
||||
|
||||
### Types
|
||||
|
||||
```go
|
||||
package data
|
||||
|
||||
import "io"
|
||||
|
||||
type Store interface {
|
||||
Open(string) (io.ReadWriteCloser, error)
|
||||
}
|
||||
```
|
||||
|
||||
### Different Implementations
|
||||
|
||||
```go
|
||||
package data
|
||||
|
||||
type StorageType int
|
||||
|
||||
const (
|
||||
DiskStorage StorageType = 1 << iota
|
||||
TempStorage
|
||||
MemoryStorage
|
||||
)
|
||||
|
||||
func NewStore(t StorageType) Store {
|
||||
switch t {
|
||||
case MemoryStorage:
|
||||
return newMemoryStorage( /*...*/ )
|
||||
case DiskStorage:
|
||||
return newDiskStorage( /*...*/ )
|
||||
default:
|
||||
return newTempStorage( /*...*/ )
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
With the factory method, the user can specify the type of storage they want.
|
||||
|
||||
```go
|
||||
s, _ := data.NewStore(data.MemoryStorage)
|
||||
f, _ := s.Open("file")
|
||||
|
||||
n, _ := f.Write([]byte("data"))
|
||||
defer f.Close()
|
||||
```
|
||||
# Factory Method Pattern
|
||||
|
||||
Factory method creational design pattern allows creating objects without having
|
||||
to specify the exact type of the object that will be created.
|
||||
工厂方法创建型设计模式允许创建对象，不用指定要创建对象的类型。
|
||||
|
||||
|
||||
## Implementation
|
||||
|
||||
The example implementation shows how to provide a data store with different
|
||||
backends such as in-memory, disk storage.
|
||||
示例实现展示了如何使用不同的后端，如内存、磁盘存储。
|
||||
|
||||
### Types(对象类型)
|
||||
|
||||
```go
|
||||
package data
|
||||
|
||||
import "io"
|
||||
|
||||
type Store interface {
|
||||
Open(string) (io.ReadWriteCloser, error)
|
||||
}
|
||||
```
|
||||
|
||||
### Different Implementations(不同实现)
|
||||
|
||||
```go
|
||||
package data
|
||||
|
||||
type StorageType int
|
||||
|
||||
// 类型实现对象枚举
|
||||
const (
|
||||
DiskStorage StorageType = 1 << iota
|
||||
TempStorage
|
||||
MemoryStorage
|
||||
)
|
||||
|
||||
// 工厂方法(实例化对象)
|
||||
func NewStore(t StorageType) Store {
|
||||
switch t {
|
||||
case MemoryStorage:
|
||||
return newMemoryStorage( /*...*/ )
|
||||
case DiskStorage:
|
||||
return newDiskStorage( /*...*/ )
|
||||
default:
|
||||
return newTempStorage( /*...*/ )
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
With the factory method, the user can specify the type of storage they want.
|
||||
使用工厂方法，指定实现类型枚举。
|
||||
|
||||
```go
|
||||
// 给工厂方法提供实现类型枚举
|
||||
s, _ := data.NewStore(data.MemoryStorage)
|
||||
f, _ := s.Open("file")
|
||||
|
||||
n, _ := f.Write([]byte("data"))
|
||||
defer f.Close()
|
||||
```
|
||||
|
||||
@ -1,48 +1,48 @@
|
||||
# Object Pool Pattern
|
||||
|
||||
The object pool creational design pattern is used to prepare and keep multiple
|
||||
instances according to the demand expectation.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package pool
|
||||
|
||||
type Pool chan *Object
|
||||
|
||||
func New(total int) *Pool {
|
||||
p := make(Pool, total)
|
||||
|
||||
for i := 0; i < total; i++ {
|
||||
p <- new(Object)
|
||||
}
|
||||
|
||||
return &p
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
Given below is a simple lifecycle example on an object pool.
|
||||
|
||||
```go
|
||||
p := pool.New(2)
|
||||
|
||||
select {
|
||||
case obj := <-p:
|
||||
obj.Do( /*...*/ )
|
||||
|
||||
p <- obj
|
||||
default:
|
||||
// No more objects left — retry later or fail
|
||||
return
|
||||
}
|
||||
```
|
||||
|
||||
## Rules of Thumb
|
||||
|
||||
- Object pool pattern is useful in cases where object initialization is more
|
||||
expensive than the object maintenance.
|
||||
- If there are spikes in demand as opposed to a steady demand, the maintenance
|
||||
overhead might overweigh the benefits of an object pool.
|
||||
- It has positive effects on performance due to objects being initialized beforehand.
|
||||
# Object Pool Pattern
|
||||
|
||||
The object pool creational design pattern is used to prepare and keep multiple
|
||||
instances according to the demand expectation.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package pool
|
||||
|
||||
type Pool chan *Object
|
||||
|
||||
func New(total int) *Pool {
|
||||
p := make(Pool, total)
|
||||
|
||||
for i := 0; i < total; i++ {
|
||||
p <- new(Object)
|
||||
}
|
||||
|
||||
return &p
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
Given below is a simple lifecycle example on an object pool.
|
||||
|
||||
```go
|
||||
p := pool.New(2)
|
||||
|
||||
select {
|
||||
case obj := <-p:
|
||||
obj.Do( /*...*/ )
|
||||
|
||||
p <- obj
|
||||
default:
|
||||
// No more objects left — retry later or fail
|
||||
return
|
||||
}
|
||||
```
|
||||
|
||||
## Rules of Thumb
|
||||
|
||||
- Object pool pattern is useful in cases where object initialization is more
|
||||
expensive than the object maintenance.
|
||||
- If there are spikes in demand as opposed to a steady demand, the maintenance
|
||||
overhead might overweigh the benefits of an object pool.
|
||||
- It has positive effects on performance due to objects being initialized beforehand.
|
||||
|
||||
@ -1,42 +1,42 @@
|
||||
# Singleton Pattern
|
||||
|
||||
Singleton creational design pattern restricts the instantiation of a type to a single object.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package singleton
|
||||
|
||||
type singleton map[string]string
|
||||
|
||||
var (
|
||||
once sync.Once
|
||||
|
||||
instance singleton
|
||||
)
|
||||
|
||||
func New() singleton {
|
||||
once.Do(func() {
|
||||
instance = make(singleton)
|
||||
})
|
||||
|
||||
return instance
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
s := singleton.New()
|
||||
|
||||
s["this"] = "that"
|
||||
|
||||
s2 := singleton.New()
|
||||
|
||||
fmt.Println("This is ", s2["this"])
|
||||
// This is that
|
||||
```
|
||||
|
||||
## Rules of Thumb
|
||||
|
||||
- Singleton pattern represents a global state and most of the time reduces testability.
|
||||
# Singleton Pattern
|
||||
|
||||
Singleton creational design pattern restricts the instantiation of a type to a single object.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package singleton
|
||||
|
||||
type singleton map[string]string
|
||||
|
||||
var (
|
||||
once sync.Once
|
||||
|
||||
instance singleton
|
||||
)
|
||||
|
||||
func New() singleton {
|
||||
once.Do(func() {
|
||||
instance = make(singleton)
|
||||
})
|
||||
|
||||
return instance
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
s := singleton.New()
|
||||
|
||||
s["this"] = "that"
|
||||
|
||||
s2 := singleton.New()
|
||||
|
||||
fmt.Println("This is ", s2["this"])
|
||||
// This is that
|
||||
```
|
||||
|
||||
## Rules of Thumb
|
||||
|
||||
- Singleton pattern represents a global state and most of the time reduces testability.
|
||||
|
||||
@ -1,94 +1,94 @@
|
||||
# Functional Options
|
||||
|
||||
Functional options are a method of implementing clean/eloquent APIs in Go.
|
||||
Options implemented as a function set the state of that option.
|
||||
|
||||
## Implementation
|
||||
|
||||
### Options
|
||||
|
||||
```go
|
||||
package file
|
||||
|
||||
type Options struct {
|
||||
UID int
|
||||
GID int
|
||||
Flags int
|
||||
Contents string
|
||||
Permissions os.FileMode
|
||||
}
|
||||
|
||||
type Option func(*Options)
|
||||
|
||||
func UID(userID int) Option {
|
||||
return func(args *Options) {
|
||||
args.UID = userID
|
||||
}
|
||||
}
|
||||
|
||||
func GID(groupID int) Option {
|
||||
return func(args *Options) {
|
||||
args.GID = groupID
|
||||
}
|
||||
}
|
||||
|
||||
func Contents(c string) Option {
|
||||
return func(args *Options) {
|
||||
args.Contents = c
|
||||
}
|
||||
}
|
||||
|
||||
func Permissions(perms os.FileMode) Option {
|
||||
return func(args *Options) {
|
||||
args.Permissions = perms
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Constructor
|
||||
|
||||
```go
|
||||
package file
|
||||
|
||||
func New(filepath string, setters ...Option) error {
|
||||
// Default Options
|
||||
args := &Options{
|
||||
UID: os.Getuid(),
|
||||
GID: os.Getgid(),
|
||||
Contents: "",
|
||||
Permissions: 0666,
|
||||
Flags: os.O_CREATE | os.O_EXCL | os.O_WRONLY,
|
||||
}
|
||||
|
||||
for _, setter := range setters {
|
||||
setter(args)
|
||||
}
|
||||
|
||||
f, err := os.OpenFile(filepath, args.Flags, args.Permissions)
|
||||
if err != nil {
|
||||
return err
|
||||
} else {
|
||||
defer f.Close()
|
||||
}
|
||||
|
||||
if _, err := f.WriteString(args.Contents); err != nil {
|
||||
return err
|
||||
}
|
||||
|
||||
return f.Chown(args.UID, args.GID)
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
emptyFile, err := file.New("/tmp/empty.txt")
|
||||
if err != nil {
|
||||
panic(err)
|
||||
}
|
||||
|
||||
fillerFile, err := file.New("/tmp/file.txt", file.UID(1000), file.Contents("Lorem Ipsum Dolor Amet"))
|
||||
if err != nil {
|
||||
panic(err)
|
||||
}
|
||||
```
|
||||
# Functional Options
|
||||
|
||||
Functional options are a method of implementing clean/eloquent APIs in Go.
|
||||
Options implemented as a function set the state of that option.
|
||||
|
||||
## Implementation
|
||||
|
||||
### Options
|
||||
|
||||
```go
|
||||
package file
|
||||
|
||||
type Options struct {
|
||||
UID int
|
||||
GID int
|
||||
Flags int
|
||||
Contents string
|
||||
Permissions os.FileMode
|
||||
}
|
||||
|
||||
type Option func(*Options)
|
||||
|
||||
func UID(userID int) Option {
|
||||
return func(args *Options) {
|
||||
args.UID = userID
|
||||
}
|
||||
}
|
||||
|
||||
func GID(groupID int) Option {
|
||||
return func(args *Options) {
|
||||
args.GID = groupID
|
||||
}
|
||||
}
|
||||
|
||||
func Contents(c string) Option {
|
||||
return func(args *Options) {
|
||||
args.Contents = c
|
||||
}
|
||||
}
|
||||
|
||||
func Permissions(perms os.FileMode) Option {
|
||||
return func(args *Options) {
|
||||
args.Permissions = perms
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Constructor
|
||||
|
||||
```go
|
||||
package file
|
||||
|
||||
func New(filepath string, setters ...Option) error {
|
||||
// Default Options
|
||||
args := &Options{
|
||||
UID: os.Getuid(),
|
||||
GID: os.Getgid(),
|
||||
Contents: "",
|
||||
Permissions: 0666,
|
||||
Flags: os.O_CREATE | os.O_EXCL | os.O_WRONLY,
|
||||
}
|
||||
|
||||
for _, setter := range setters {
|
||||
setter(args)
|
||||
}
|
||||
|
||||
f, err := os.OpenFile(filepath, args.Flags, args.Permissions)
|
||||
if err != nil {
|
||||
return err
|
||||
} else {
|
||||
defer f.Close()
|
||||
}
|
||||
|
||||
if _, err := f.WriteString(args.Contents); err != nil {
|
||||
return err
|
||||
}
|
||||
|
||||
return f.Chown(args.UID, args.GID)
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
emptyFile, err := file.New("/tmp/empty.txt")
|
||||
if err != nil {
|
||||
panic(err)
|
||||
}
|
||||
|
||||
fillerFile, err := file.New("/tmp/file.txt", file.UID(1000), file.Contents("Lorem Ipsum Dolor Amet"))
|
||||
if err != nil {
|
||||
panic(err)
|
||||
}
|
||||
```
|
||||
|
||||
@ -1,40 +1,40 @@
|
||||
Fan-In Messaging Patterns
|
||||
===================================
|
||||
Fan-In is a messaging pattern used to create a funnel for work amongst workers (clients: source, server: destination).
|
||||
|
||||
We can model fan-in using the Go channels.
|
||||
|
||||
```go
|
||||
// Merge different channels in one channel
|
||||
func Merge(cs ...<-chan int) <-chan int {
|
||||
var wg sync.WaitGroup
|
||||
|
||||
out := make(chan int)
|
||||
|
||||
// Start an send goroutine for each input channel in cs. send
|
||||
// copies values from c to out until c is closed, then calls wg.Done.
|
||||
send := func(c <-chan int) {
|
||||
for n := range c {
|
||||
out <- n
|
||||
}
|
||||
wg.Done()
|
||||
}
|
||||
|
||||
wg.Add(len(cs))
|
||||
for _, c := range cs {
|
||||
go send(c)
|
||||
}
|
||||
|
||||
// Start a goroutine to close out once all the send goroutines are
|
||||
// done. This must start after the wg.Add call.
|
||||
go func() {
|
||||
wg.Wait()
|
||||
close(out)
|
||||
}()
|
||||
return out
|
||||
}
|
||||
```
|
||||
|
||||
The `Merge` function converts a list of channels to a single channel by starting a goroutine for each inbound channel that copies the values to the sole outbound channel.
|
||||
|
||||
Once all the output goroutines have been started, `Merge` a goroutine is started to close the main channel.
|
||||
Fan-In Messaging Patterns
|
||||
===================================
|
||||
Fan-In is a messaging pattern used to create a funnel for work amongst workers (clients: source, server: destination).
|
||||
|
||||
We can model fan-in using the Go channels.
|
||||
|
||||
```go
|
||||
// Merge different channels in one channel
|
||||
func Merge(cs ...<-chan int) <-chan int {
|
||||
var wg sync.WaitGroup
|
||||
|
||||
out := make(chan int)
|
||||
|
||||
// Start an send goroutine for each input channel in cs. send
|
||||
// copies values from c to out until c is closed, then calls wg.Done.
|
||||
send := func(c <-chan int) {
|
||||
for n := range c {
|
||||
out <- n
|
||||
}
|
||||
wg.Done()
|
||||
}
|
||||
|
||||
wg.Add(len(cs))
|
||||
for _, c := range cs {
|
||||
go send(c)
|
||||
}
|
||||
|
||||
// Start a goroutine to close out once all the send goroutines are
|
||||
// done. This must start after the wg.Add call.
|
||||
go func() {
|
||||
wg.Wait()
|
||||
close(out)
|
||||
}()
|
||||
return out
|
||||
}
|
||||
```
|
||||
|
||||
The `Merge` function converts a list of channels to a single channel by starting a goroutine for each inbound channel that copies the values to the sole outbound channel.
|
||||
|
||||
Once all the output goroutines have been started, `Merge` a goroutine is started to close the main channel.
|
||||
|
||||
@ -1,47 +1,47 @@
|
||||
Fan-Out Messaging Pattern
|
||||
=========================
|
||||
Fan-Out is a messaging pattern used for distributing work amongst workers (producer: source, consumers: destination).
|
||||
|
||||
We can model fan-out using the Go channels.
|
||||
|
||||
```go
|
||||
// Split a channel into n channels that receive messages in a round-robin fashion.
|
||||
func Split(ch <-chan int, n int) []<-chan int {
|
||||
cs := make([]chan int)
|
||||
for i := 0; i < n; i++ {
|
||||
cs = append(cs, make(chan int))
|
||||
}
|
||||
|
||||
// Distributes the work in a round robin fashion among the stated number
|
||||
// of channels until the main channel has been closed. In that case, close
|
||||
// all channels and return.
|
||||
distributeToChannels := func(ch <-chan int, cs []chan<- int) {
|
||||
// Close every channel when the execution ends.
|
||||
defer func(cs []chan<- int) {
|
||||
for _, c := range cs {
|
||||
close(c)
|
||||
}
|
||||
}(cs)
|
||||
|
||||
for {
|
||||
for _, c := range cs {
|
||||
select {
|
||||
case val, ok := <-ch:
|
||||
if !ok {
|
||||
return
|
||||
}
|
||||
|
||||
c <- val
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
go distributeToChannels(ch, cs)
|
||||
|
||||
return cs
|
||||
}
|
||||
```
|
||||
|
||||
The `Split` function converts a single channel into a list of channels by using
|
||||
a goroutine to copy received values to channels in the list in a round-robin fashion.
|
||||
Fan-Out Messaging Pattern
|
||||
=========================
|
||||
Fan-Out is a messaging pattern used for distributing work amongst workers (producer: source, consumers: destination).
|
||||
|
||||
We can model fan-out using the Go channels.
|
||||
|
||||
```go
|
||||
// Split a channel into n channels that receive messages in a round-robin fashion.
|
||||
func Split(ch <-chan int, n int) []<-chan int {
|
||||
cs := make([]chan int)
|
||||
for i := 0; i < n; i++ {
|
||||
cs = append(cs, make(chan int))
|
||||
}
|
||||
|
||||
// Distributes the work in a round robin fashion among the stated number
|
||||
// of channels until the main channel has been closed. In that case, close
|
||||
// all channels and return.
|
||||
distributeToChannels := func(ch <-chan int, cs []chan<- int) {
|
||||
// Close every channel when the execution ends.
|
||||
defer func(cs []chan<- int) {
|
||||
for _, c := range cs {
|
||||
close(c)
|
||||
}
|
||||
}(cs)
|
||||
|
||||
for {
|
||||
for _, c := range cs {
|
||||
select {
|
||||
case val, ok := <-ch:
|
||||
if !ok {
|
||||
return
|
||||
}
|
||||
|
||||
c <- val
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
go distributeToChannels(ch, cs)
|
||||
|
||||
return cs
|
||||
}
|
||||
```
|
||||
|
||||
The `Split` function converts a single channel into a list of channels by using
|
||||
a goroutine to copy received values to channels in the list in a round-robin fashion.
|
||||
|
||||
@ -1,80 +1,80 @@
|
||||
Publish & Subscribe Messaging Pattern
|
||||
============
|
||||
Publish-Subscribe is a messaging pattern used to communicate messages between
|
||||
different components without these components knowing anything about each other's identity.
|
||||
|
||||
It is similar to the Observer behavioral design pattern.
|
||||
The fundamental design principals of both Observer and Publish-Subscribe is the decoupling of
|
||||
those interested in being informed about `Event Messages` from the informer (Observers or Publishers).
|
||||
Meaning that you don't have to program the messages to be sent directly to specific receivers.
|
||||
|
||||
To accomplish this, an intermediary, called a "message broker" or "event bus",
|
||||
receives published messages, and then routes them on to subscribers.
|
||||
|
||||
|
||||
There are three components **messages**, **topics**, **users**.
|
||||
|
||||
```go
|
||||
type Message struct {
|
||||
// Contents
|
||||
}
|
||||
|
||||
|
||||
type Subscription struct {
|
||||
ch chan<- Message
|
||||
|
||||
Inbox chan Message
|
||||
}
|
||||
|
||||
func (s *Subscription) Publish(msg Message) error {
|
||||
if _, ok := <-s.ch; !ok {
|
||||
return errors.New("Topic has been closed")
|
||||
}
|
||||
|
||||
s.ch <- msg
|
||||
|
||||
return nil
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
type Topic struct {
|
||||
Subscribers []Session
|
||||
MessageHistory []Message
|
||||
}
|
||||
|
||||
func (t *Topic) Subscribe(uid uint64) (Subscription, error) {
|
||||
// Get session and create one if it's the first
|
||||
|
||||
// Add session to the Topic & MessageHistory
|
||||
|
||||
// Create a subscription
|
||||
}
|
||||
|
||||
func (t *Topic) Unsubscribe(Subscription) error {
|
||||
// Implementation
|
||||
}
|
||||
|
||||
func (t *Topic) Delete() error {
|
||||
// Implementation
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
type User struct {
|
||||
ID uint64
|
||||
Name string
|
||||
}
|
||||
|
||||
type Session struct {
|
||||
User User
|
||||
Timestamp time.Time
|
||||
}
|
||||
```
|
||||
|
||||
Improvements
|
||||
============
|
||||
Events can be published in a parallel fashion by utilizing stackless goroutines.
|
||||
|
||||
Performance can be improved by dealing with straggler subscribers
|
||||
by using a buffered inbox and you stop sending events once the inbox is full.
|
||||
Publish & Subscribe Messaging Pattern
|
||||
============
|
||||
Publish-Subscribe is a messaging pattern used to communicate messages between
|
||||
different components without these components knowing anything about each other's identity.
|
||||
|
||||
It is similar to the Observer behavioral design pattern.
|
||||
The fundamental design principals of both Observer and Publish-Subscribe is the decoupling of
|
||||
those interested in being informed about `Event Messages` from the informer (Observers or Publishers).
|
||||
Meaning that you don't have to program the messages to be sent directly to specific receivers.
|
||||
|
||||
To accomplish this, an intermediary, called a "message broker" or "event bus",
|
||||
receives published messages, and then routes them on to subscribers.
|
||||
|
||||
|
||||
There are three components **messages**, **topics**, **users**.
|
||||
|
||||
```go
|
||||
type Message struct {
|
||||
// Contents
|
||||
}
|
||||
|
||||
|
||||
type Subscription struct {
|
||||
ch chan<- Message
|
||||
|
||||
Inbox chan Message
|
||||
}
|
||||
|
||||
func (s *Subscription) Publish(msg Message) error {
|
||||
if _, ok := <-s.ch; !ok {
|
||||
return errors.New("Topic has been closed")
|
||||
}
|
||||
|
||||
s.ch <- msg
|
||||
|
||||
return nil
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
type Topic struct {
|
||||
Subscribers []Session
|
||||
MessageHistory []Message
|
||||
}
|
||||
|
||||
func (t *Topic) Subscribe(uid uint64) (Subscription, error) {
|
||||
// Get session and create one if it's the first
|
||||
|
||||
// Add session to the Topic & MessageHistory
|
||||
|
||||
// Create a subscription
|
||||
}
|
||||
|
||||
func (t *Topic) Unsubscribe(Subscription) error {
|
||||
// Implementation
|
||||
}
|
||||
|
||||
func (t *Topic) Delete() error {
|
||||
// Implementation
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
type User struct {
|
||||
ID uint64
|
||||
Name string
|
||||
}
|
||||
|
||||
type Session struct {
|
||||
User User
|
||||
Timestamp time.Time
|
||||
}
|
||||
```
|
||||
|
||||
Improvements
|
||||
============
|
||||
Events can be published in a parallel fashion by utilizing stackless goroutines.
|
||||
|
||||
Performance can be improved by dealing with straggler subscribers
|
||||
by using a buffered inbox and you stop sending events once the inbox is full.
|
||||
|
||||
@ -1,40 +1,40 @@
|
||||
# Timing Functions
|
||||
|
||||
When optimizing code, sometimes a quick and dirty time measurement is required
|
||||
as opposed to utilizing profiler tools/frameworks to validate assumptions.
|
||||
|
||||
Time measurements can be performed by utilizing `time` package and `defer` statements.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package profile
|
||||
|
||||
import (
|
||||
"time"
|
||||
"log"
|
||||
)
|
||||
|
||||
func Duration(invocation time.Time, name string) {
|
||||
elapsed := time.Since(invocation)
|
||||
|
||||
log.Printf("%s lasted %s", name, elapsed)
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
func BigIntFactorial(x big.Int) *big.Int {
|
||||
// Arguments to a defer statement is immediately evaluated and stored.
|
||||
// The deferred function receives the pre-evaluated values when its invoked.
|
||||
defer profile.Duration(time.Now(), "IntFactorial")
|
||||
|
||||
y := big.NewInt(1)
|
||||
for one := big.NewInt(1); x.Sign() > 0; x.Sub(x, one) {
|
||||
y.Mul(y, x)
|
||||
}
|
||||
|
||||
return x.Set(y)
|
||||
}
|
||||
```
|
||||
# Timing Functions
|
||||
|
||||
When optimizing code, sometimes a quick and dirty time measurement is required
|
||||
as opposed to utilizing profiler tools/frameworks to validate assumptions.
|
||||
|
||||
Time measurements can be performed by utilizing `time` package and `defer` statements.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package profile
|
||||
|
||||
import (
|
||||
"time"
|
||||
"log"
|
||||
)
|
||||
|
||||
func Duration(invocation time.Time, name string) {
|
||||
elapsed := time.Since(invocation)
|
||||
|
||||
log.Printf("%s lasted %s", name, elapsed)
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
|
||||
```go
|
||||
func BigIntFactorial(x big.Int) *big.Int {
|
||||
// Arguments to a defer statement is immediately evaluated and stored.
|
||||
// The deferred function receives the pre-evaluated values when its invoked.
|
||||
defer profile.Duration(time.Now(), "IntFactorial")
|
||||
|
||||
y := big.NewInt(1)
|
||||
for one := big.NewInt(1); x.Sign() > 0; x.Sub(x, one) {
|
||||
y.Mul(y, x)
|
||||
}
|
||||
|
||||
return x.Set(y)
|
||||
}
|
||||
```
|
||||
|
||||
@ -1,102 +1,102 @@
|
||||
# Circuit Breaker Pattern
|
||||
|
||||
Similar to electrical fuses that prevent fires when a circuit that is connected
|
||||
to the electrical grid starts drawing a high amount of power which causes the
|
||||
wires to heat up and combust, the circuit breaker design pattern is a fail-first
|
||||
mechanism that shuts down the circuit, request/response relationship or a
|
||||
service in the case of software development, to prevent bigger failures.
|
||||
|
||||
**Note:** The words "circuit" and "service" are used synonymously throught this
|
||||
document.
|
||||
|
||||
## Implementation
|
||||
|
||||
Below is the implementation of a very simple circuit breaker to illustrate the purpose
|
||||
of the circuit breaker design pattern.
|
||||
|
||||
### Operation Counter
|
||||
|
||||
`circuit.Counter` is a simple counter that records success and failure states of
|
||||
a circuit along with a timestamp and calculates the consecutive number of
|
||||
failures.
|
||||
|
||||
```go
|
||||
package circuit
|
||||
|
||||
import (
|
||||
"time"
|
||||
)
|
||||
|
||||
type State int
|
||||
|
||||
const (
|
||||
UnknownState State = iota
|
||||
FailureState
|
||||
SuccessState
|
||||
)
|
||||
|
||||
type Counter interface {
|
||||
Count(State)
|
||||
ConsecutiveFailures() uint32
|
||||
LastActivity() time.Time
|
||||
Reset()
|
||||
}
|
||||
```
|
||||
|
||||
### Circuit Breaker
|
||||
|
||||
Circuit is wrapped using the `circuit.Breaker` closure that keeps an internal operation counter.
|
||||
It returns a fast error if the circuit has failed consecutively more than the specified threshold.
|
||||
After a while it retries the request and records it.
|
||||
|
||||
**Note:** Context type is used here to carry deadlines, cancelation signals, and
|
||||
other request-scoped values across API boundaries and between processes.
|
||||
|
||||
```go
|
||||
package circuit
|
||||
|
||||
import (
|
||||
"context"
|
||||
"time"
|
||||
)
|
||||
|
||||
type Circuit func(context.Context) error
|
||||
|
||||
func Breaker(c Circuit, failureThreshold uint32) Circuit {
|
||||
cnt := NewCounter()
|
||||
|
||||
return func(ctx context) error {
|
||||
if cnt.ConsecutiveFailures() >= failureThreshold {
|
||||
canRetry := func(cnt Counter) {
|
||||
backoffLevel := Cnt.ConsecutiveFailures() - failureThreshold
|
||||
|
||||
// Calculates when should the circuit breaker resume propagating requests
|
||||
// to the service
|
||||
shouldRetryAt := cnt.LastActivity().Add(time.Seconds * 2 << backoffLevel)
|
||||
|
||||
return time.Now().After(shouldRetryAt)
|
||||
}
|
||||
|
||||
if !canRetry(cnt) {
|
||||
// Fails fast instead of propagating requests to the circuit since
|
||||
// not enough time has passed since the last failure to retry
|
||||
return ErrServiceUnavailable
|
||||
}
|
||||
}
|
||||
|
||||
// Unless the failure threshold is exceeded the wrapped service mimics the
|
||||
// old behavior and the difference in behavior is seen after consecutive failures
|
||||
if err := c(ctx); err != nil {
|
||||
cnt.Count(FailureState)
|
||||
return err
|
||||
}
|
||||
|
||||
cnt.Count(SuccessState)
|
||||
return nil
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Related Works
|
||||
|
||||
- [sony/gobreaker](https://github.com/sony/gobreaker) is a well-tested and intuitive circuit breaker implementation for real-world use cases.
|
||||
# Circuit Breaker Pattern
|
||||
|
||||
Similar to electrical fuses that prevent fires when a circuit that is connected
|
||||
to the electrical grid starts drawing a high amount of power which causes the
|
||||
wires to heat up and combust, the circuit breaker design pattern is a fail-first
|
||||
mechanism that shuts down the circuit, request/response relationship or a
|
||||
service in the case of software development, to prevent bigger failures.
|
||||
|
||||
**Note:** The words "circuit" and "service" are used synonymously throught this
|
||||
document.
|
||||
|
||||
## Implementation
|
||||
|
||||
Below is the implementation of a very simple circuit breaker to illustrate the purpose
|
||||
of the circuit breaker design pattern.
|
||||
|
||||
### Operation Counter
|
||||
|
||||
`circuit.Counter` is a simple counter that records success and failure states of
|
||||
a circuit along with a timestamp and calculates the consecutive number of
|
||||
failures.
|
||||
|
||||
```go
|
||||
package circuit
|
||||
|
||||
import (
|
||||
"time"
|
||||
)
|
||||
|
||||
type State int
|
||||
|
||||
const (
|
||||
UnknownState State = iota
|
||||
FailureState
|
||||
SuccessState
|
||||
)
|
||||
|
||||
type Counter interface {
|
||||
Count(State)
|
||||
ConsecutiveFailures() uint32
|
||||
LastActivity() time.Time
|
||||
Reset()
|
||||
}
|
||||
```
|
||||
|
||||
### Circuit Breaker
|
||||
|
||||
Circuit is wrapped using the `circuit.Breaker` closure that keeps an internal operation counter.
|
||||
It returns a fast error if the circuit has failed consecutively more than the specified threshold.
|
||||
After a while it retries the request and records it.
|
||||
|
||||
**Note:** Context type is used here to carry deadlines, cancelation signals, and
|
||||
other request-scoped values across API boundaries and between processes.
|
||||
|
||||
```go
|
||||
package circuit
|
||||
|
||||
import (
|
||||
"context"
|
||||
"time"
|
||||
)
|
||||
|
||||
type Circuit func(context.Context) error
|
||||
|
||||
func Breaker(c Circuit, failureThreshold uint32) Circuit {
|
||||
cnt := NewCounter()
|
||||
|
||||
return func(ctx context) error {
|
||||
if cnt.ConsecutiveFailures() >= failureThreshold {
|
||||
canRetry := func(cnt Counter) {
|
||||
backoffLevel := Cnt.ConsecutiveFailures() - failureThreshold
|
||||
|
||||
// Calculates when should the circuit breaker resume propagating requests
|
||||
// to the service
|
||||
shouldRetryAt := cnt.LastActivity().Add(time.Seconds * 2 << backoffLevel)
|
||||
|
||||
return time.Now().After(shouldRetryAt)
|
||||
}
|
||||
|
||||
if !canRetry(cnt) {
|
||||
// Fails fast instead of propagating requests to the circuit since
|
||||
// not enough time has passed since the last failure to retry
|
||||
return ErrServiceUnavailable
|
||||
}
|
||||
}
|
||||
|
||||
// Unless the failure threshold is exceeded the wrapped service mimics the
|
||||
// old behavior and the difference in behavior is seen after consecutive failures
|
||||
if err := c(ctx); err != nil {
|
||||
cnt.Count(FailureState)
|
||||
return err
|
||||
}
|
||||
|
||||
cnt.Count(SuccessState)
|
||||
return nil
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Related Works
|
||||
|
||||
- [sony/gobreaker](https://github.com/sony/gobreaker) is a well-tested and intuitive circuit breaker implementation for real-world use cases.
|
||||
|
||||
@ -1,41 +1,41 @@
|
||||
# Decorator Pattern
|
||||
Decorator structural pattern allows extending the function of an existing object dynamically without altering its internals.
|
||||
|
||||
Decorators provide a flexible method to extend functionality of objects.
|
||||
|
||||
## Implementation
|
||||
`LogDecorate` decorates a function with the signature `func(int) int` that
|
||||
manipulates integers and adds input/output logging capabilities.
|
||||
|
||||
```go
|
||||
type Object func(int) int
|
||||
|
||||
func LogDecorate(fn Object) Object {
|
||||
return func(n int) int {
|
||||
log.Println("Starting the execution with the integer", n)
|
||||
|
||||
result := fn(n)
|
||||
|
||||
log.Println("Execution is completed with the result", result)
|
||||
|
||||
return result
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
```go
|
||||
func Double(n int) int {
|
||||
return n * 2
|
||||
}
|
||||
|
||||
f := LogDecorate(Double)
|
||||
|
||||
f(5)
|
||||
// Starting execution with the integer 5
|
||||
// Execution is completed with the result 10
|
||||
```
|
||||
|
||||
## Rules of Thumb
|
||||
- Unlike Adapter pattern, the object to be decorated is obtained by **injection**.
|
||||
- Decorators should not alter the interface of an object.
|
||||
# Decorator Pattern
|
||||
Decorator structural pattern allows extending the function of an existing object dynamically without altering its internals.
|
||||
|
||||
Decorators provide a flexible method to extend functionality of objects.
|
||||
|
||||
## Implementation
|
||||
`LogDecorate` decorates a function with the signature `func(int) int` that
|
||||
manipulates integers and adds input/output logging capabilities.
|
||||
|
||||
```go
|
||||
type Object func(int) int
|
||||
|
||||
func LogDecorate(fn Object) Object {
|
||||
return func(n int) int {
|
||||
log.Println("Starting the execution with the integer", n)
|
||||
|
||||
result := fn(n)
|
||||
|
||||
log.Println("Execution is completed with the result", result)
|
||||
|
||||
return result
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
```go
|
||||
func Double(n int) int {
|
||||
return n * 2
|
||||
}
|
||||
|
||||
f := LogDecorate(Double)
|
||||
|
||||
f(5)
|
||||
// Starting execution with the integer 5
|
||||
// Execution is completed with the result 10
|
||||
```
|
||||
|
||||
## Rules of Thumb
|
||||
- Unlike Adapter pattern, the object to be decorated is obtained by **injection**.
|
||||
- Decorators should not alter the interface of an object.
|
||||
|
||||
@ -1,45 +1,45 @@
|
||||
# Proxy Pattern
|
||||
|
||||
The [proxy pattern](https://en.wikipedia.org/wiki/Proxy_pattern) provides an object that controls access to another object, intercepting all calls.
|
||||
|
||||
## Implementation
|
||||
|
||||
The proxy could interface to anything: a network connection, a large object in memory, a file, or some other resource that is expensive or impossible to duplicate.
|
||||
|
||||
Short idea of implementation:
|
||||
```go
|
||||
// To use proxy and to object they must implement same methods
|
||||
type IObject interface {
|
||||
ObjDo(action string)
|
||||
}
|
||||
|
||||
// Object represents real objects which proxy will delegate data
|
||||
type Object struct {
|
||||
action string
|
||||
}
|
||||
|
||||
// ObjDo implements IObject interface and handel's all logic
|
||||
func (obj *Object) ObjDo(action string) {
|
||||
// Action behavior
|
||||
fmt.Printf("I can, %s", action)
|
||||
}
|
||||
|
||||
// ProxyObject represents proxy object with intercepts actions
|
||||
type ProxyObject struct {
|
||||
object *Object
|
||||
}
|
||||
|
||||
// ObjDo are implemented IObject and intercept action before send in real Object
|
||||
func (p *ProxyObject) ObjDo(action string) {
|
||||
if p.object == nil {
|
||||
p.object = new(Object)
|
||||
}
|
||||
if action == "Run" {
|
||||
p.object.ObjDo(action) // Prints: I can, Run
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
More complex usage of proxy as example: User creates "Terminal" authorizes and PROXY send execution command to real Terminal object
|
||||
See [proxy/main.go](proxy/main.go) or [view in the Playground](https://play.golang.org/p/mnjKCMaOVE).
|
||||
# Proxy Pattern
|
||||
|
||||
The [proxy pattern](https://en.wikipedia.org/wiki/Proxy_pattern) provides an object that controls access to another object, intercepting all calls.
|
||||
|
||||
## Implementation
|
||||
|
||||
The proxy could interface to anything: a network connection, a large object in memory, a file, or some other resource that is expensive or impossible to duplicate.
|
||||
|
||||
Short idea of implementation:
|
||||
```go
|
||||
// To use proxy and to object they must implement same methods
|
||||
type IObject interface {
|
||||
ObjDo(action string)
|
||||
}
|
||||
|
||||
// Object represents real objects which proxy will delegate data
|
||||
type Object struct {
|
||||
action string
|
||||
}
|
||||
|
||||
// ObjDo implements IObject interface and handel's all logic
|
||||
func (obj *Object) ObjDo(action string) {
|
||||
// Action behavior
|
||||
fmt.Printf("I can, %s", action)
|
||||
}
|
||||
|
||||
// ProxyObject represents proxy object with intercepts actions
|
||||
type ProxyObject struct {
|
||||
object *Object
|
||||
}
|
||||
|
||||
// ObjDo are implemented IObject and intercept action before send in real Object
|
||||
func (p *ProxyObject) ObjDo(action string) {
|
||||
if p.object == nil {
|
||||
p.object = new(Object)
|
||||
}
|
||||
if action == "Run" {
|
||||
p.object.ObjDo(action) // Prints: I can, Run
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
More complex usage of proxy as example: User creates "Terminal" authorizes and PROXY send execution command to real Terminal object
|
||||
See [proxy/main.go](proxy/main.go) or [view in the Playground](https://play.golang.org/p/mnjKCMaOVE).
|
||||
|
||||
@ -1,127 +1,127 @@
|
||||
package main
|
||||
|
||||
import (
|
||||
"fmt"
|
||||
)
|
||||
|
||||
// For example:
|
||||
// we must a execute some command
|
||||
// so before that we must to create new terminal session
|
||||
// and provide our user name and command
|
||||
func main() {
|
||||
// Create new instance of Proxy terminal
|
||||
t, err := NewTerminal("gopher")
|
||||
if err != nil {
|
||||
// panic: User cant be empty
|
||||
// Or
|
||||
// panic: You (badUser) are not allowed to use terminal and execute commands
|
||||
panic(err.Error())
|
||||
}
|
||||
|
||||
// Execute user command
|
||||
excResp, excErr := t.Execute("say_hi") // Proxy prints to STDOUT -> PROXY: Intercepted execution of user (gopher), asked command (say_hi)
|
||||
if excErr != nil {
|
||||
fmt.Printf("ERROR: %s\n", excErr.Error()) // Prints: ERROR: I know only how to execute commands: say_hi, man
|
||||
}
|
||||
|
||||
// Show execution response
|
||||
fmt.Println(excResp) // Prints: gopher@go_term$: Hi gopher
|
||||
}
|
||||
|
||||
/*
|
||||
From that it's can be different terminals realizations with different methods, propertys, yda yda...
|
||||
*/
|
||||
|
||||
// ITerminal is interface, it's a public method whose implemented in Terminal(Proxy) and Gopher Terminal
|
||||
type ITerminal interface {
|
||||
Execute(cmd string) (resp string, err error)
|
||||
}
|
||||
|
||||
// GopherTerminal for example:
|
||||
// Its a "huge" structure with different public methods
|
||||
type GopherTerminal struct {
|
||||
// user is a current authorized user
|
||||
User string
|
||||
}
|
||||
|
||||
// Execute just runs known commands for current authorized user
|
||||
func (gt *GopherTerminal) Execute(cmd string) (resp string, err error) {
|
||||
// Set "terminal" prefix for output
|
||||
prefix := fmt.Sprintf("%s@go_term$:", gt.User)
|
||||
|
||||
// Execute some asked commands if we know them
|
||||
switch cmd {
|
||||
case "say_hi":
|
||||
resp = fmt.Sprintf("%s Hi %s", prefix, gt.User)
|
||||
case "man":
|
||||
resp = fmt.Sprintf("%s Visit 'https://golang.org/doc/' for Golang documentation", prefix)
|
||||
default:
|
||||
err = fmt.Errorf("%s Unknown command", prefix)
|
||||
}
|
||||
|
||||
return
|
||||
}
|
||||
|
||||
/*
|
||||
And now we will create owr proxy to deliver user and commands to specific objects
|
||||
*/
|
||||
|
||||
// Terminal is a implementation of Proxy, it's validates and sends data to GopherTerminal
|
||||
// As example before send commands, user must be authorized
|
||||
type Terminal struct {
|
||||
currentUser string
|
||||
gopherTerminal *GopherTerminal
|
||||
}
|
||||
|
||||
// NewTerminal creates new instance of terminal
|
||||
func NewTerminal(user string) (t *Terminal, err error) {
|
||||
// Check user if given correctly
|
||||
if user == "" {
|
||||
err = fmt.Errorf("User cant be empty")
|
||||
return
|
||||
}
|
||||
|
||||
// Before we execute user commands, we validate current user, if he have rights to do it
|
||||
if authErr := authorizeUser(user); authErr != nil {
|
||||
err = fmt.Errorf("You (%s) are not allowed to use terminal and execute commands", user)
|
||||
return
|
||||
}
|
||||
|
||||
// Create new instance of terminal and set valid user
|
||||
t = &Terminal{currentUser: user}
|
||||
|
||||
return
|
||||
}
|
||||
|
||||
// Execute intercepts execution of command, implements authorizing user, validates it and
|
||||
// poxing command to real terminal (gopherTerminal) method
|
||||
func (t *Terminal) Execute(command string) (resp string, err error) {
|
||||
// If user allowed to execute send commands then, for example we can decide which terminal can be used, remote or local etc..
|
||||
// but for example we just creating new instance of terminal,
|
||||
// set current user and send user command to execution in terminal
|
||||
t.gopherTerminal = &GopherTerminal{User: t.currentUser}
|
||||
|
||||
// For example our proxy can log or output intercepted execution... etc
|
||||
fmt.Printf("PROXY: Intercepted execution of user (%s), asked command (%s)\n", t.currentUser, command)
|
||||
|
||||
// Transfer data to original object and execute command
|
||||
if resp, err = t.gopherTerminal.Execute(command); err != nil {
|
||||
err = fmt.Errorf("I know only how to execute commands: say_hi, man")
|
||||
return
|
||||
}
|
||||
|
||||
return
|
||||
}
|
||||
|
||||
// authorize validates user right to execute commands
|
||||
func authorizeUser(user string) (err error) {
|
||||
// As we use terminal like proxy, then
|
||||
// we will intercept user name to validate if it's allowed to execute commands
|
||||
if user != "gopher" {
|
||||
// Do some logs, notifications etc...
|
||||
err = fmt.Errorf("User %s in black list", user)
|
||||
return
|
||||
}
|
||||
|
||||
return
|
||||
}
|
||||
package main
|
||||
|
||||
import (
|
||||
"fmt"
|
||||
)
|
||||
|
||||
// For example:
|
||||
// we must a execute some command
|
||||
// so before that we must to create new terminal session
|
||||
// and provide our user name and command
|
||||
func main() {
|
||||
// Create new instance of Proxy terminal
|
||||
t, err := NewTerminal("gopher")
|
||||
if err != nil {
|
||||
// panic: User cant be empty
|
||||
// Or
|
||||
// panic: You (badUser) are not allowed to use terminal and execute commands
|
||||
panic(err.Error())
|
||||
}
|
||||
|
||||
// Execute user command
|
||||
excResp, excErr := t.Execute("say_hi") // Proxy prints to STDOUT -> PROXY: Intercepted execution of user (gopher), asked command (say_hi)
|
||||
if excErr != nil {
|
||||
fmt.Printf("ERROR: %s\n", excErr.Error()) // Prints: ERROR: I know only how to execute commands: say_hi, man
|
||||
}
|
||||
|
||||
// Show execution response
|
||||
fmt.Println(excResp) // Prints: gopher@go_term$: Hi gopher
|
||||
}
|
||||
|
||||
/*
|
||||
From that it's can be different terminals realizations with different methods, propertys, yda yda...
|
||||
*/
|
||||
|
||||
// ITerminal is interface, it's a public method whose implemented in Terminal(Proxy) and Gopher Terminal
|
||||
type ITerminal interface {
|
||||
Execute(cmd string) (resp string, err error)
|
||||
}
|
||||
|
||||
// GopherTerminal for example:
|
||||
// Its a "huge" structure with different public methods
|
||||
type GopherTerminal struct {
|
||||
// user is a current authorized user
|
||||
User string
|
||||
}
|
||||
|
||||
// Execute just runs known commands for current authorized user
|
||||
func (gt *GopherTerminal) Execute(cmd string) (resp string, err error) {
|
||||
// Set "terminal" prefix for output
|
||||
prefix := fmt.Sprintf("%s@go_term$:", gt.User)
|
||||
|
||||
// Execute some asked commands if we know them
|
||||
switch cmd {
|
||||
case "say_hi":
|
||||
resp = fmt.Sprintf("%s Hi %s", prefix, gt.User)
|
||||
case "man":
|
||||
resp = fmt.Sprintf("%s Visit 'https://golang.org/doc/' for Golang documentation", prefix)
|
||||
default:
|
||||
err = fmt.Errorf("%s Unknown command", prefix)
|
||||
}
|
||||
|
||||
return
|
||||
}
|
||||
|
||||
/*
|
||||
And now we will create owr proxy to deliver user and commands to specific objects
|
||||
*/
|
||||
|
||||
// Terminal is a implementation of Proxy, it's validates and sends data to GopherTerminal
|
||||
// As example before send commands, user must be authorized
|
||||
type Terminal struct {
|
||||
currentUser string
|
||||
gopherTerminal *GopherTerminal
|
||||
}
|
||||
|
||||
// NewTerminal creates new instance of terminal
|
||||
func NewTerminal(user string) (t *Terminal, err error) {
|
||||
// Check user if given correctly
|
||||
if user == "" {
|
||||
err = fmt.Errorf("User cant be empty")
|
||||
return
|
||||
}
|
||||
|
||||
// Before we execute user commands, we validate current user, if he have rights to do it
|
||||
if authErr := authorizeUser(user); authErr != nil {
|
||||
err = fmt.Errorf("You (%s) are not allowed to use terminal and execute commands", user)
|
||||
return
|
||||
}
|
||||
|
||||
// Create new instance of terminal and set valid user
|
||||
t = &Terminal{currentUser: user}
|
||||
|
||||
return
|
||||
}
|
||||
|
||||
// Execute intercepts execution of command, implements authorizing user, validates it and
|
||||
// poxing command to real terminal (gopherTerminal) method
|
||||
func (t *Terminal) Execute(command string) (resp string, err error) {
|
||||
// If user allowed to execute send commands then, for example we can decide which terminal can be used, remote or local etc..
|
||||
// but for example we just creating new instance of terminal,
|
||||
// set current user and send user command to execution in terminal
|
||||
t.gopherTerminal = &GopherTerminal{User: t.currentUser}
|
||||
|
||||
// For example our proxy can log or output intercepted execution... etc
|
||||
fmt.Printf("PROXY: Intercepted execution of user (%s), asked command (%s)\n", t.currentUser, command)
|
||||
|
||||
// Transfer data to original object and execute command
|
||||
if resp, err = t.gopherTerminal.Execute(command); err != nil {
|
||||
err = fmt.Errorf("I know only how to execute commands: say_hi, man")
|
||||
return
|
||||
}
|
||||
|
||||
return
|
||||
}
|
||||
|
||||
// authorize validates user right to execute commands
|
||||
func authorizeUser(user string) (err error) {
|
||||
// As we use terminal like proxy, then
|
||||
// we will intercept user name to validate if it's allowed to execute commands
|
||||
if user != "gopher" {
|
||||
// Do some logs, notifications etc...
|
||||
err = fmt.Errorf("User %s in black list", user)
|
||||
return
|
||||
}
|
||||
|
||||
return
|
||||
}
|
||||
|
||||
@ -1,84 +1,84 @@
|
||||
# Semaphore Pattern
|
||||
A semaphore is a synchronization pattern/primitive that imposes mutual exclusion on a limited number of resources.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package semaphore
|
||||
|
||||
var (
|
||||
ErrNoTickets = errors.New("semaphore: could not aquire semaphore")
|
||||
ErrIllegalRelease = errors.New("semaphore: can't release the semaphore without acquiring it first")
|
||||
)
|
||||
|
||||
// Interface contains the behavior of a semaphore that can be acquired and/or released.
|
||||
type Interface interface {
|
||||
Acquire() error
|
||||
Release() error
|
||||
}
|
||||
|
||||
type implementation struct {
|
||||
sem chan struct{}
|
||||
timeout time.Duration
|
||||
}
|
||||
|
||||
func (s *implementation) Acquire() error {
|
||||
select {
|
||||
case s.sem <- struct{}{}:
|
||||
return nil
|
||||
case <-time.After(s.timeout):
|
||||
return ErrNoTickets
|
||||
}
|
||||
}
|
||||
|
||||
func (s *implementation) Release() error {
|
||||
select {
|
||||
case _ = <-s.sem:
|
||||
return nil
|
||||
case <-time.After(s.timeout):
|
||||
return ErrIllegalRelease
|
||||
}
|
||||
|
||||
return nil
|
||||
}
|
||||
|
||||
func New(tickets int, timeout time.Duration) Interface {
|
||||
return &implementation{
|
||||
sem: make(chan struct{}, tickets),
|
||||
timeout: timeout,
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
### Semaphore with Timeouts
|
||||
|
||||
```go
|
||||
tickets, timeout := 1, 3*time.Second
|
||||
s := semaphore.New(tickets, timeout)
|
||||
|
||||
if err := s.Acquire(); err != nil {
|
||||
panic(err)
|
||||
}
|
||||
|
||||
// Do important work
|
||||
|
||||
if err := s.Release(); err != nil {
|
||||
panic(err)
|
||||
}
|
||||
```
|
||||
### Semaphore without Timeouts (Non-Blocking)
|
||||
|
||||
```go
|
||||
tickets, timeout := 0, 0
|
||||
s := semaphore.New(tickets, timeout)
|
||||
|
||||
if err := s.Acquire(); err != nil {
|
||||
if err != semaphore.ErrNoTickets {
|
||||
panic(err)
|
||||
}
|
||||
|
||||
// No tickets left, can't work :(
|
||||
os.Exit(1)
|
||||
}
|
||||
```
|
||||
# Semaphore Pattern
|
||||
A semaphore is a synchronization pattern/primitive that imposes mutual exclusion on a limited number of resources.
|
||||
|
||||
## Implementation
|
||||
|
||||
```go
|
||||
package semaphore
|
||||
|
||||
var (
|
||||
ErrNoTickets = errors.New("semaphore: could not aquire semaphore")
|
||||
ErrIllegalRelease = errors.New("semaphore: can't release the semaphore without acquiring it first")
|
||||
)
|
||||
|
||||
// Interface contains the behavior of a semaphore that can be acquired and/or released.
|
||||
type Interface interface {
|
||||
Acquire() error
|
||||
Release() error
|
||||
}
|
||||
|
||||
type implementation struct {
|
||||
sem chan struct{}
|
||||
timeout time.Duration
|
||||
}
|
||||
|
||||
func (s *implementation) Acquire() error {
|
||||
select {
|
||||
case s.sem <- struct{}{}:
|
||||
return nil
|
||||
case <-time.After(s.timeout):
|
||||
return ErrNoTickets
|
||||
}
|
||||
}
|
||||
|
||||
func (s *implementation) Release() error {
|
||||
select {
|
||||
case _ = <-s.sem:
|
||||
return nil
|
||||
case <-time.After(s.timeout):
|
||||
return ErrIllegalRelease
|
||||
}
|
||||
|
||||
return nil
|
||||
}
|
||||
|
||||
func New(tickets int, timeout time.Duration) Interface {
|
||||
return &implementation{
|
||||
sem: make(chan struct{}, tickets),
|
||||
timeout: timeout,
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Usage
|
||||
### Semaphore with Timeouts
|
||||
|
||||
```go
|
||||
tickets, timeout := 1, 3*time.Second
|
||||
s := semaphore.New(tickets, timeout)
|
||||
|
||||
if err := s.Acquire(); err != nil {
|
||||
panic(err)
|
||||
}
|
||||
|
||||
// Do important work
|
||||
|
||||
if err := s.Release(); err != nil {
|
||||
panic(err)
|
||||
}
|
||||
```
|
||||
### Semaphore without Timeouts (Non-Blocking)
|
||||
|
||||
```go
|
||||
tickets, timeout := 0, 0
|
||||
s := semaphore.New(tickets, timeout)
|
||||
|
||||
if err := s.Acquire(); err != nil {
|
||||
if err != semaphore.ErrNoTickets {
|
||||
panic(err)
|
||||
}
|
||||
|
||||
// No tickets left, can't work :(
|
||||
os.Exit(1)
|
||||
}
|
||||
```
|
||||
|
||||
Loading…
Reference in New Issue
Block a user