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<li class="chapter " data-level="1.1" data-path="../">
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<a href="../">
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Go Patterns
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<a href="../#creational-patterns">
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Creational Patterns
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</a>
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Abstract Factory
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</a>
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Builder
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Factory Method
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Object Pool
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<li class="chapter " data-level="1.1.1.5" data-path="../creational/singleton.html">
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<a href="../creational/singleton.html">
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Singleton
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</a>
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</li>
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</ul>
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<li class="chapter " data-level="1.1.2" data-path="../">
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<a href="../#structural-patterns">
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Structural Patterns
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<ul class="articles">
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<li class="chapter " data-level="1.1.2.1" data-path="../structural/bridge.md">
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<span>
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Bridge
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</a>
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</li>
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<li class="chapter " data-level="1.1.2.2" data-path="../structural/composite.md">
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<span>
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Composite
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</a>
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</li>
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<li class="chapter " data-level="1.1.2.3" data-path="../structural/decorator.html">
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<a href="../structural/decorator.html">
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Decorator
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</a>
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</li>
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<li class="chapter " data-level="1.1.2.4" data-path="../structural/facade.md">
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<span>
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Facade
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</a>
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</li>
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<li class="chapter " data-level="1.1.2.5" data-path="../structural/flyweight.md">
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<span>
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Flyweight
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</a>
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</li>
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<li class="chapter " data-level="1.1.2.6" data-path="../structural/proxy.md">
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<span>
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Proxy
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="1.1.3" data-path="../">
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<a href="../#behavioral-patterns">
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Behavioral Patterns
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</a>
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<ul class="articles">
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<li class="chapter " data-level="1.1.3.1" data-path="../behavioral/chain_of_responsibility.md">
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<span>
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Chain of Responsibility
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.2" data-path="../behavioral/command.md">
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<span>
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Command
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.3" data-path="../behavioral/mediator.md">
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<span>
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Mediator
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.4" data-path="../behavioral/memento.md">
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<span>
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Memento
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.5" data-path="../behavioral/observer.html">
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<a href="../behavioral/observer.html">
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Observer
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.6" data-path="../behavioral/registry.md">
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<span>
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Registry
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.7" data-path="../behavioral/state.md">
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<span>
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State
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.8" data-path="../behavioral/strategy.html">
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<a href="../behavioral/strategy.html">
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Strategy
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.9" data-path="../behavioral/template.md">
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<span>
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Template
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</a>
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</li>
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<li class="chapter " data-level="1.1.3.10" data-path="../behavioral/visitor.md">
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<span>
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Visitor
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="1.1.4" data-path="../">
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<a href="../#synchronization-patterns">
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Synchronization Patterns
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</a>
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<ul class="articles">
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<li class="chapter " data-level="1.1.4.1" data-path="condition_variable.md">
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<span>
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Condition Variable
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</a>
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</li>
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<li class="chapter " data-level="1.1.4.2" data-path="mutex.md">
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<span>
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Lock/Mutex
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</a>
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</li>
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<li class="chapter " data-level="1.1.4.3" data-path="monitor.md">
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<span>
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Monitor
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</a>
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</li>
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<li class="chapter " data-level="1.1.4.4" data-path="read_write_lock.md">
|
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<span>
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Read-Write Lock
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</a>
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</li>
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<li class="chapter active" data-level="1.1.4.5" data-path="semaphore.html">
|
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<a href="semaphore.html">
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Semaphore
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</a>
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</li>
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</ul>
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</li>
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<li class="chapter " data-level="1.1.5" data-path="../">
|
||
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<a href="../#concurrency-patterns">
|
||
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Concurrency Patterns
|
||
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|
||
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</a>
|
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<ul class="articles">
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<li class="chapter " data-level="1.1.5.1" data-path="../concurrency/barrier.md">
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<span>
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N-Barrier
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</a>
|
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</li>
|
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<li class="chapter " data-level="1.1.5.2" data-path="../concurrency/bounded_parallelism.html">
|
||
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|
||
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<a href="../concurrency/bounded_parallelism.html">
|
||
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Bounded Parallelism
|
||
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||
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</a>
|
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</li>
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<li class="chapter " data-level="1.1.5.3" data-path="../concurrency/broadcast.md">
|
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<span>
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Broadcast
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||
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</a>
|
||
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</li>
|
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<li class="chapter " data-level="1.1.5.4" data-path="../concurrency/coroutine.md">
|
||
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<span>
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||
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Coroutines
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||
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</a>
|
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</li>
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<li class="chapter " data-level="1.1.5.5" data-path="../concurrency/generator.html">
|
||
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||
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<a href="../concurrency/generator.html">
|
||
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Generators
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||
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||
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</a>
|
||
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</li>
|
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<li class="chapter " data-level="1.1.5.6" data-path="../concurrency/reactor.md">
|
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<span>
|
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Reactor
|
||
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</a>
|
||
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</li>
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<li class="chapter " data-level="1.1.5.7" data-path="../concurrency/parallelism.html">
|
||
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||
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<a href="../concurrency/parallelism.html">
|
||
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Parallelism
|
||
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|
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</a>
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</li>
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<li class="chapter " data-level="1.1.5.8" data-path="../concurrency/producer_consumer.md">
|
||
|
|
||
|
<span>
|
||
|
|
||
|
|
||
|
Producer Consumer
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
||
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|
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|
||
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</ul>
|
||
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|
||
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</li>
|
||
|
|
||
|
<li class="chapter " data-level="1.1.6" data-path="../">
|
||
|
|
||
|
<a href="../#messaging-patterns">
|
||
|
|
||
|
|
||
|
Messaging Patterns
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
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|
||
|
<ul class="articles">
|
||
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||
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|
||
|
<li class="chapter " data-level="1.1.6.1" data-path="../messaging/fan_in.html">
|
||
|
|
||
|
<a href="../messaging/fan_in.html">
|
||
|
|
||
|
|
||
|
Fan-In
|
||
|
|
||
|
</a>
|
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|
||
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</li>
|
||
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<li class="chapter " data-level="1.1.6.2" data-path="../messaging/fan_out.html">
|
||
|
|
||
|
<a href="../messaging/fan_out.html">
|
||
|
|
||
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|
||
|
Fan-Out
|
||
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|
||
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</a>
|
||
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||
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|
||
|
</li>
|
||
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||
|
<li class="chapter " data-level="1.1.6.3" data-path="../messaging/futures_promises.md">
|
||
|
|
||
|
<span>
|
||
|
|
||
|
|
||
|
Futures & Promises
|
||
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|
||
|
</a>
|
||
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||
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|
||
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|
||
|
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|
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||
|
<li class="chapter " data-level="1.1.6.4" data-path="../messaging/publish_subscribe.html">
|
||
|
|
||
|
<a href="../messaging/publish_subscribe.html">
|
||
|
|
||
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|
||
|
Publish/Subscribe
|
||
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|
||
|
</a>
|
||
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|
||
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|
||
|
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|
||
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||
|
<li class="chapter " data-level="1.1.6.5" data-path="../messaging/push_pull.md">
|
||
|
|
||
|
<span>
|
||
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|
||
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|
||
|
Push & Pull
|
||
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|
||
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</a>
|
||
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||
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||
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|
||
|
</li>
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</ul>
|
||
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</li>
|
||
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|
||
|
<li class="chapter " data-level="1.1.7" data-path="../">
|
||
|
|
||
|
<a href="../#stability-patterns">
|
||
|
|
||
|
|
||
|
Stability Patterns
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
<ul class="articles">
|
||
|
|
||
|
|
||
|
<li class="chapter " data-level="1.1.7.1" data-path="../stability/bulkhead.md">
|
||
|
|
||
|
<span>
|
||
|
|
||
|
|
||
|
Bulkheads
|
||
|
|
||
|
</a>
|
||
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|
||
|
|
||
|
|
||
|
</li>
|
||
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|
||
|
<li class="chapter " data-level="1.1.7.2" data-path="../stability/circuit-breaker.html">
|
||
|
|
||
|
<a href="../stability/circuit-breaker.html">
|
||
|
|
||
|
|
||
|
Circuit-Breaker
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
||
|
|
||
|
<li class="chapter " data-level="1.1.7.3" data-path="../stability/deadline.md">
|
||
|
|
||
|
<span>
|
||
|
|
||
|
|
||
|
Deadline
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
||
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|
||
|
<li class="chapter " data-level="1.1.7.4" data-path="../stability/fail_fast.md">
|
||
|
|
||
|
<span>
|
||
|
|
||
|
|
||
|
Fail-Fast
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
||
|
|
||
|
<li class="chapter " data-level="1.1.7.5" data-path="../stability/handshaking.md">
|
||
|
|
||
|
<span>
|
||
|
|
||
|
|
||
|
Handshaking
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
||
|
|
||
|
<li class="chapter " data-level="1.1.7.6" data-path="../stability/steady_state.md">
|
||
|
|
||
|
<span>
|
||
|
|
||
|
|
||
|
Steady-State
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
||
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|
||
|
|
||
|
</ul>
|
||
|
|
||
|
</li>
|
||
|
|
||
|
<li class="chapter " data-level="1.1.8" data-path="../">
|
||
|
|
||
|
<a href="../#profiling-patterns">
|
||
|
|
||
|
|
||
|
Profiling Patterns
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
<ul class="articles">
|
||
|
|
||
|
|
||
|
<li class="chapter " data-level="1.1.8.1" data-path="../profiling/timing.html">
|
||
|
|
||
|
<a href="../profiling/timing.html">
|
||
|
|
||
|
|
||
|
Timing Functions
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
||
|
|
||
|
|
||
|
</ul>
|
||
|
|
||
|
</li>
|
||
|
|
||
|
<li class="chapter " data-level="1.1.9" data-path="../">
|
||
|
|
||
|
<a href="../#idioms">
|
||
|
|
||
|
|
||
|
Idioms
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
<ul class="articles">
|
||
|
|
||
|
|
||
|
<li class="chapter " data-level="1.1.9.1" data-path="../idiom/functional-options.html">
|
||
|
|
||
|
<a href="../idiom/functional-options.html">
|
||
|
|
||
|
|
||
|
Functional Options
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
||
|
|
||
|
|
||
|
</ul>
|
||
|
|
||
|
</li>
|
||
|
|
||
|
<li class="chapter " data-level="1.1.10" data-path="../">
|
||
|
|
||
|
<a href="../#anti-patterns">
|
||
|
|
||
|
|
||
|
Anti-Patterns
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
<ul class="articles">
|
||
|
|
||
|
|
||
|
<li class="chapter " data-level="1.1.10.1" data-path="../anti-patterns/cascading_failures.md">
|
||
|
|
||
|
<span>
|
||
|
|
||
|
|
||
|
Cascading Failures
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
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|
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</li>
|
||
|
|
||
|
<li class="chapter " data-level="1.2" data-path="../CONTRIBUTING.html">
|
||
|
|
||
|
<a href="../CONTRIBUTING.html">
|
||
|
|
||
|
|
||
|
Contributing
|
||
|
|
||
|
</a>
|
||
|
|
||
|
|
||
|
|
||
|
</li>
|
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|
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|
||
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|
||
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<li class="divider"></li>
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|
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|
<li>
|
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|
<a href="https://www.gitbook.com" target="blank" class="gitbook-link">
|
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|
Published with GitBook
|
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|
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</nav>
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<div class="book-body">
|
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<div class="body-inner">
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<div class="book-header" role="navigation">
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|
||
|
|
||
|
<!-- Title -->
|
||
|
<h1>
|
||
|
<i class="fa fa-circle-o-notch fa-spin"></i>
|
||
|
<a href=".." >Semaphore</a>
|
||
|
</h1>
|
||
|
</div>
|
||
|
|
||
|
|
||
|
|
||
|
|
||
|
<div class="page-wrapper" tabindex="-1" role="main">
|
||
|
<div class="page-inner">
|
||
|
|
||
|
<section class="normal markdown-section">
|
||
|
|
||
|
<h1 id="semaphore-pattern">Semaphore Pattern</h1>
|
||
|
<p>A semaphore is a synchronization pattern/primitive that imposes mutual exclusion on a limited number of resources. </p>
|
||
|
<h2 id="implementation">Implementation</h2>
|
||
|
<pre><code class="lang-go"><span class="hljs-keyword">package</span> semaphore
|
||
|
|
||
|
<span class="hljs-keyword">var</span> (
|
||
|
ErrNoTickets = errors.New(<span class="hljs-string">"semaphore: could not aquire semaphore"</span>)
|
||
|
ErrIllegalRelease = errors.New(<span class="hljs-string">"semaphore: can't release the semaphore without acquiring it first"</span>)
|
||
|
)
|
||
|
|
||
|
<span class="hljs-comment">// Interface contains the behavior of a semaphore that can be acquired and/or released.</span>
|
||
|
<span class="hljs-keyword">type</span> Interface <span class="hljs-keyword">interface</span> {
|
||
|
Acquire() error
|
||
|
Release() error
|
||
|
}
|
||
|
|
||
|
<span class="hljs-keyword">type</span> implementation <span class="hljs-keyword">struct</span> {
|
||
|
sem <span class="hljs-keyword">chan</span> <span class="hljs-keyword">struct</span>{}
|
||
|
timeout time.Duration
|
||
|
}
|
||
|
|
||
|
<span class="hljs-keyword">func</span> (s *implementation) Acquire() error {
|
||
|
<span class="hljs-keyword">select</span> {
|
||
|
<span class="hljs-keyword">case</span> s.sem <- <span class="hljs-keyword">struct</span>{}{}:
|
||
|
<span class="hljs-keyword">return</span> <span class="hljs-literal">nil</span>
|
||
|
<span class="hljs-keyword">case</span> <-time.After(s.timeout):
|
||
|
<span class="hljs-keyword">return</span> ErrNoTickets
|
||
|
}
|
||
|
}
|
||
|
|
||
|
<span class="hljs-keyword">func</span> (s *implementation) Release() error {
|
||
|
<span class="hljs-keyword">select</span> {
|
||
|
<span class="hljs-keyword">case</span> _ = <-s.sem:
|
||
|
<span class="hljs-keyword">return</span> <span class="hljs-literal">nil</span>
|
||
|
<span class="hljs-keyword">case</span> <-time.After(s.timeout):
|
||
|
<span class="hljs-keyword">return</span> ErrIllegalRelease
|
||
|
}
|
||
|
|
||
|
<span class="hljs-keyword">return</span> <span class="hljs-literal">nil</span>
|
||
|
}
|
||
|
|
||
|
<span class="hljs-keyword">func</span> New(tickets <span class="hljs-keyword">int</span>, timeout time.Duration) Interface {
|
||
|
<span class="hljs-keyword">return</span> &implementation{
|
||
|
sem: <span class="hljs-built_in">make</span>(<span class="hljs-keyword">chan</span> <span class="hljs-keyword">struct</span>{}, tickets),
|
||
|
timeout: timeout,
|
||
|
}
|
||
|
}
|
||
|
</code></pre>
|
||
|
<h2 id="usage">Usage</h2>
|
||
|
<h3 id="semaphore-with-timeouts">Semaphore with Timeouts</h3>
|
||
|
<pre><code class="lang-go">tickets, timeout := <span class="hljs-number">1</span>, <span class="hljs-number">3</span>*time.Second
|
||
|
s := semaphore.New(tickets, timeout)
|
||
|
|
||
|
<span class="hljs-keyword">if</span> err := s.Acquire(); err != <span class="hljs-literal">nil</span> {
|
||
|
<span class="hljs-built_in">panic</span>(err)
|
||
|
}
|
||
|
|
||
|
<span class="hljs-comment">// Do important work</span>
|
||
|
|
||
|
<span class="hljs-keyword">if</span> err := s.Release(); err != <span class="hljs-literal">nil</span> {
|
||
|
<span class="hljs-built_in">panic</span>(err)
|
||
|
}
|
||
|
</code></pre>
|
||
|
<h3 id="semaphore-without-timeouts-non-blocking">Semaphore without Timeouts (Non-Blocking)</h3>
|
||
|
<pre><code class="lang-go">tickets, timeout := <span class="hljs-number">0</span>, <span class="hljs-number">0</span>
|
||
|
s := semaphore.New(tickets, timeout)
|
||
|
|
||
|
<span class="hljs-keyword">if</span> err := s.Acquire(); err != <span class="hljs-literal">nil</span> {
|
||
|
<span class="hljs-keyword">if</span> err != semaphore.ErrNoTickets {
|
||
|
<span class="hljs-built_in">panic</span>(err)
|
||
|
}
|
||
|
|
||
|
<span class="hljs-comment">// No tickets left, can't work :(</span>
|
||
|
os.Exit(<span class="hljs-number">1</span>)
|
||
|
}
|
||
|
</code></pre>
|
||
|
|
||
|
|
||
|
</section>
|
||
|
|
||
|
</div>
|
||
|
</div>
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|
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||
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<script src="../gitbook/gitbook-plugin-sharing/buttons.js"></script>
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<script src="../gitbook/gitbook-plugin-fontsettings/fontsettings.js"></script>
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</body>
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</html>
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