Graceful disconnect upon context cancel

Make sure the underlying library context cancellation happens only
after the session has been shutdown.

Signed-off-by: Luca Bigliardi <shammash@google.com>

context.go

@@ -0,0 +1,50 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+	"os/signal"
+	"sync"
+)
+
+func WithSignal(ctx context.Context, s ...os.Signal) (context.Context, context.CancelFunc) {
+	sigCtx, cancel := context.WithCancel(ctx)
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, s...)
+	go func() {
+		select {
+		case <-c:
+			log.Printf("Received %s, exiting", s)
+			cancel()
+		case <-ctx.Done():
+			cancel()
+		}
+		signal.Stop(c)
+	}()
+	return sigCtx, cancel
+}
+
+func WithWaitGroup(ctx context.Context, wg *sync.WaitGroup) context.Context {
+	wgCtx, cancel := context.WithCancel(context.Background())
+	go func() {
+		<-ctx.Done()
+		wg.Wait()
+		cancel()
+	}()
+	return wgCtx
+}

irc.go

@@ -92,6 +92,7 @@ type IRCNotifier struct {
 	sessionUp         bool
 	sessionUpSignal   chan bool
 	sessionDownSignal chan bool
+	sessionWg         sync.WaitGroup
 
 	channelReconciler *ChannelReconciler
 
@@ -212,19 +213,19 @@ func (n *IRCNotifier) SendAlertMsg(ctx context.Context, alertMsg *AlertMsg) {
 }
 
 func (n *IRCNotifier) ShutdownPhase() {
-	if n.Client.Connected() {
+	if n.sessionUp {
 		log.Printf("IRC client connected, quitting")
 		n.Client.Quit("see ya")
 
-		if n.sessionUp {
-			log.Printf("Session is up, wait for IRC disconnect to complete")
+		log.Printf("Wait for IRC disconnect to complete")
 		select {
 		case <-n.sessionDownSignal:
 		case <-time.After(n.Client.Config().Timeout):
 			log.Printf("Timeout while waiting for IRC disconnect to complete, stopping anyway")
 		}
+		n.sessionWg.Done()
 	}
-	}
+	log.Printf("IRC shutdown complete")
 }
 
 func (n *IRCNotifier) ConnectedPhase(ctx context.Context) {
@@ -233,6 +234,7 @@ func (n *IRCNotifier) ConnectedPhase(ctx context.Context) {
 		n.SendAlertMsg(ctx, &alertMsg)
 	case <-n.sessionDownSignal:
 		n.sessionUp = false
+		n.sessionWg.Done()
 		n.channelReconciler.Stop()
 		n.Client.Quit("see ya")
 		ircConnectedGauge.Set(0)
@@ -247,7 +249,7 @@ func (n *IRCNotifier) SetupPhase(ctx context.Context) {
 		if ok := n.BackoffCounter.DelayContext(ctx); !ok {
 			return
 		}
-		if err := n.Client.ConnectContext(ctx); err != nil {
+		if err := n.Client.ConnectContext(WithWaitGroup(ctx, &n.sessionWg)); err != nil {
 			log.Printf("Could not connect to IRC: %s", err)
 			return
 		}
@@ -256,6 +258,7 @@ func (n *IRCNotifier) SetupPhase(ctx context.Context) {
 	select {
 	case <-n.sessionUpSignal:
 		n.sessionUp = true
+		n.sessionWg.Add(1)
 		n.MaybeIdentifyNick()
 		n.channelReconciler.Start(ctx)
 		ircConnectedGauge.Set(1)

irc_test.go

@@ -582,7 +582,6 @@ func TestStopRunningWhenHalfConnected(t *testing.T) {
 	expectedCommands := []string{
 		"NICK foo",
 		"USER foo 12 * :",
-		"QUIT :see ya",
 	}
 
 	if !reflect.DeepEqual(expectedCommands, server.Log) {

main.go

@@ -18,29 +18,10 @@ import (
 	"context"
 	"flag"
 	"log"
-	"os"
-	"os/signal"
 	"sync"
 	"syscall"
 )
 
-func WithSignal(ctx context.Context, s ...os.Signal) (context.Context, context.CancelFunc) {
-	ctx, cancel := context.WithCancel(ctx)
-	c := make(chan os.Signal, 1)
-	signal.Notify(c, s...)
-	go func() {
-		select {
-		case <-c:
-			log.Printf("Received %s, exiting", s)
-			cancel()
-		case <-ctx.Done():
-			cancel()
-		}
-		signal.Stop(c)
-	}()
-	return ctx, cancel
-}
-
 func main() {
 
 	configFile := flag.String("config", "", "Config file path.")