add os signal subscriber

README.md

@@ -1,2 +1,9 @@
-# os-signal-subscriber
-Signal subscriber that allows you to attach a callback to an `os.Signal` notification
+# signal
+This repository provides helpers with signals
+
+## Subscriber
+Signal subscriber that allows you to attach a callback to an `os.Signal` notification.
+
+Useful to react to any os.Signal.
+
+It returns an `unsubscribe` function that can gracefully stop some http server and clean allocated object

go.mod

@@ -0,0 +1,8 @@
+module github.com/gol4ng/signal
+
+go 1.12
+
+require (
+	bou.ke/monkey v1.0.1
+	github.com/stretchr/testify v1.3.0
+)

go.sum

@@ -0,0 +1,9 @@
+bou.ke/monkey v1.0.1 h1:zEMLInw9xvNakzUUPjfS4Ds6jYPqCFx3m7bRmG5NH2U=
+bou.ke/monkey v1.0.1/go.mod h1:FgHuK96Rv2Nlf+0u1OOVDpCMdsWyOFmeeketDHE7LIg=
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=

subscriber.go

@@ -0,0 +1,46 @@
+package signal
+
+import (
+	"os"
+	"os/signal"
+)
+
+// This is a really simple signal subscriber
+// Signal subscriber that allows you to attach a callback to an `os.Signal` notification.
+// Usefull to react to any os.Signal.
+// It returns an `unsubscribe` function that stops the goroutine and clean allocated object
+//
+// Example:
+// unsubscriber := signal.subscribe(func(s os.Signal) {
+//   fmt.Println("process as been asked to be stopped")
+// }, os.SIGSTOP)
+//
+// call "unsubscriber()" in order to detach your callback and clean memory
+//
+// if no 2nd arg is passed, the `callback` func will be called everytime an os.Signal is triggered
+// signal.subscribe(func(s os.Signal) {fmt.Println("called for any signal")})
+//
+// /!\ CAUTION /!\
+// If you call it with second arg to `nil`, no signal will be listened
+// signal.subscribe(func(s os.Signal) {fmt.Println("NEVER BE CALLED")}, nil)
+func Subscribe(callback func(os.Signal), signals ...os.Signal) func() {
+	signalChan := make(chan os.Signal, 1)
+	stopChan := make(chan struct{}, 1)
+	signal.Notify(signalChan, signals...)
+	go func() {
+		for {
+			select {
+			case <-stopChan:
+				signal.Stop(signalChan)
+				close(stopChan)
+				close(signalChan)
+				return
+			case sig := <-signalChan:
+				go callback(sig)
+			}
+		}
+	}()
+	return func() {
+		stopChan <- struct{}{}
+	}
+}

subscriber_test.go

@@ -0,0 +1,74 @@
+package signal_test
+
+import (
+	"os"
+	"os/signal"
+	"testing"
+	"time"
+	"unsafe"
+
+	"bou.ke/monkey"
+
+	"github.com/stretchr/testify/assert"
+
+	sig "github.com/gol4ng/signal"
+)
+
+func TestSubscribe(t *testing.T) {
+	var signalChan chan<- os.Signal
+	var subscribedSignals = []os.Signal{os.Interrupt, os.Kill}
+	var realSignal = os.Interrupt
+	var callbackCalled = false
+
+	monkey.Patch(signal.Notify, func(c chan<- os.Signal, signals ...os.Signal) {
+		// get subscriber internal chan in order to simulate signal receive
+		signalChan = c
+		for _, s := range subscribedSignals {
+			assert.Contains(t, signals, s)
+		}
+	})
+	defer monkey.UnpatchAll()
+
+	sig.Subscribe(func(signal os.Signal) {
+		assert.Equal(t, realSignal, signal, "wrong signal ingested by subscriber.")
+		callbackCalled = true
+	}, subscribedSignals...)
+
+	// simulate signal receive
+	signalChan <- realSignal
+	// wait for goroutine callback func fulfilment (@see subscriber.go `go callback(subscribedSignals)`)
+	time.Sleep(1 * time.Millisecond)
+	assert.True(t, callbackCalled, "callback func should be called.")
+}
+
+func TestUnSubscribe(t *testing.T) {
+	var signalChan chan<- os.Signal
+	var subscribedSignal = os.Interrupt
+	var stopCalled = false
+	var callbackCalled = false
+
+	monkey.Patch(signal.Notify, func(c chan<- os.Signal, signals ...os.Signal) {
+		// get subscriber internal chan in order to simulate signal receive
+		signalChan = c
+		assert.Equal(t, subscribedSignal, signals[0])
+	})
+	monkey.Patch(signal.Stop, func(c chan<- os.Signal) {
+		assert.Equal(t, signalChan, c)
+		stopCalled = true
+	})
+	defer monkey.UnpatchAll()
+
+	unsubscribeFunc := sig.Subscribe(func(signal os.Signal) {
+		assert.Equal(t, signal, subscribedSignal, "wrong signal ingested by subscriber.")
+		callbackCalled = true
+	}, subscribedSignal)
+
+	unsubscribeFunc()
+	// wait for goroutine signal.Stop func call (@see subscriber.go `case <-stopChan:`)
+	time.Sleep(1 * time.Millisecond)
+	// `signalChan` is a bidirectional chan as it is equal to the `subscriber signalChan` value
+	_, ok := <-*(*chan os.Signal)(unsafe.Pointer(&signalChan))
+	assert.False(t, ok, "signal channel should be closed.")
+	assert.True(t, stopCalled, "`signal.Stop` should be called when `unsubscribeFunc` is called.")
+	assert.False(t, callbackCalled, "callback func should not be called as `unsubscribeFunc` is called.")
+}