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Rewrite fan-in/out messaging patterns
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@ -77,8 +77,8 @@ __Messaging Patterns__:
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| Pattern | Description |
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|:-------:| ----------- |
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| [Fan-In](fan/fan_in.go) | Funnels tasks to a work sink (e.g. server) |
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| [Fan-Out](fan/fan_out.go) | Distributes tasks amongs workers |
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| [Fan-In](messaging/fan_in.md) | Funnels tasks to a work sink (e.g. server) |
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| [Fan-Out](messaging/fan_out.md) | Distributes tasks amongs workers (e.g. producer) |
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| [Futures & Promises](futures_promises.go) | Acts as a place-holder of a result that is initally unknown for synchronization purposes |
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| [Publish/Subscribe](messaging/publish_subscribe.md) | Passes information to a collection of recipients who subscribed to a topic |
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| [Push & Pull](push_pull.go) | Distributes messages to multiple workers, arranged in a pipeline |
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@ -1,33 +0,0 @@
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package fan
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import "sync"
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// In implements fan.In messaging pattern
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// Merges different channels in one channel
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func In(cs ...<-chan int) <-chan int {
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var wg sync.WaitGroup
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out := make(chan int)
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// Start an send goroutine for each input channel in cs. send
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// copies values from c to out until c is closed, then calls wg.Done.
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send := func(c <-chan int) {
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for n := range c {
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out <- n
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}
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wg.Done()
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}
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wg.Add(len(cs))
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for _, c := range cs {
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go send(c)
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}
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// Start a goroutine to close out once all the send goroutines are
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// done. This must start after the wg.Add call.
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go func() {
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wg.Wait()
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close(out)
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}()
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return out
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}
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40
messaging/fan_in.md
Normal file
40
messaging/fan_in.md
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@ -0,0 +1,40 @@
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Fan-In Messaging Patterns
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===================================
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Fan-In is a messaging pattern used to create a funnel for work amongst workers (clients: source, server: destination).
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We can model fan-in using the Go channels.
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```go
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// Merge different channels in one channel
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func Merge(cs ...<-chan int) <-chan int {
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var wg sync.WaitGroup
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out := make(chan int)
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// Start an send goroutine for each input channel in cs. send
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// copies values from c to out until c is closed, then calls wg.Done.
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send := func(c <-chan int) {
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for n := range c {
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out <- n
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}
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wg.Done()
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}
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wg.Add(len(cs))
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for _, c := range cs {
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go send(c)
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}
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// Start a goroutine to close out once all the send goroutines are
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// done. This must start after the wg.Add call.
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go func() {
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wg.Wait()
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close(out)
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}()
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return out
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}
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```
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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.
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Once all the output goroutines have been started, `Merge` a goroutine is started to close the main channel.
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@ -1,9 +1,12 @@
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package fan
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Fan-Out Messaging Pattern
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=========================
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Fan-Out is a messaging pattern used for distributing work amongst workers (producer: source, consumers: destination).
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// Out implements fan.Out messaging pattern
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// Split a channel into n channels that receive messages
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// in a round-robin fashion.
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func Out(ch <-chan int, n int) []<-chan int {
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We can model fan-out using the Go channels.
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```go
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// Split a channel into n channels that receive messages in a round-robin fashion.
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func Split(ch <-chan int, n int) []<-chan int {
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cs := make([]chan int)
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for i := 0; i < n; i++ {
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cs = append(cs, make(chan int))
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@ -38,3 +41,7 @@ func Out(ch <-chan int, n int) []<-chan int {
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return cs
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}
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```
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The `Split` function converts a single channel into a list of channels by using
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a goroutine to copy received values to channels in the list in a round-robin fashion.
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