cmd: handle signals via NotifyContext

Install a single signal.NotifyContext in main and let the HTTP and SMTP
servers register a context.AfterFunc that shuts them down when the shared
context is cancelled, instead of each wiring up its own os/signal channel.
This drops the duplicated signal plumbing.

Derive the shutdown timeout from a fresh background context. The signal
already cancels the parent context, so reusing it as the timeout parent
would make the graceful shutdown deadline expire immediately.

Signed-off-by: Robin Jarry <robin@jarry.cc>

Author: rjarry

cmd/pw/http/main.go

@@ -7,12 +7,10 @@ package http
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"net/http"
-	"os"
-	"os/signal"
-	"syscall"
 	"time"
 
 	"github.com/getpatchwork/patchwork/cmd/pw/pw"
@@ -57,26 +55,21 @@ func (c *CLI) Run(ctx context.Context) error {
 		return fmt.Errorf("listen: %w", err)
 	}
 
-	done := make(chan os.Signal, 1)
-	signal.Notify(done, syscall.SIGINT, syscall.SIGTERM)
+	log.Noticef("patchwork %s listening on http://%s", version, sock.Addr())
 
-	go func() {
-		log.Noticef("patchwork %s listening on http://%s", version, sock.Addr())
-		if e := srv.Serve(sock); e != nil && e != http.ErrServerClosed {
-			err = fmt.Errorf("serve: %w", e)
-			done <- syscall.SIGCHLD
-		}
-	}()
-
-	sig := <-done
-	if sig != syscall.SIGCHLD {
-		log.Noticef("received signal %v, shutting down", sig)
-		timeout, cancel := context.WithTimeout(ctx, 30*time.Second)
+	unregister := context.AfterFunc(ctx, func() {
+		log.Noticef("%s, shutting down", context.Cause(ctx))
+		timeout, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 		defer cancel()
 		if e := srv.Shutdown(timeout); e != nil {
-			err = fmt.Errorf("shutdown: %w", e)
+			log.Errorf("shutdown: %v", e)
 		}
+	})
+	defer unregister()
+
+	if err = srv.Serve(sock); err != nil && !errors.Is(err, http.ErrServerClosed) {
+		return fmt.Errorf("serve: %w", err)
 	}
 
-	return err
+	return nil
 }

cmd/pw/ingress/main.go

@@ -13,9 +13,7 @@ import (
 	"io"
 	"net"
 	"os"
-	"os/signal"
 	"strings"
-	"syscall"
 	"time"
 
 	"github.com/emersion/go-mbox"
@@ -87,28 +85,23 @@ func (c *CLI) Run(ctx context.Context) error {
 		return fmt.Errorf("smtp: %w", err)
 	}
 
-	done := make(chan os.Signal, 1)
-	signal.Notify(done, syscall.SIGINT, syscall.SIGTERM)
+	log.Noticef("patchwork %s listening on smtp://%s", pw.GetVersion(ctx), sock.Addr())
 
-	go func() {
-		log.Noticef("patchwork %s listening on smtp://%s", pw.GetVersion(ctx), sock.Addr())
-		if e := srv.Serve(sock); e != nil && !errors.Is(e, net.ErrClosed) {
-			err = fmt.Errorf("serve: %w", e)
-			done <- syscall.SIGCHLD
-		}
-	}()
-
-	sig := <-done
-	if sig != syscall.SIGCHLD {
-		log.Noticef("received signal %v, shutting down", sig)
-		timeout, cancel := context.WithTimeout(ctx, 30*time.Second)
+	unregister := context.AfterFunc(ctx, func() {
+		log.Noticef("%s, shutting down", context.Cause(ctx))
+		timeout, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 		defer cancel()
 		if e := srv.Shutdown(timeout); e != nil {
-			err = fmt.Errorf("shutdown: %w", e)
+			log.Errorf("shutdown: %v", e)
 		}
+	})
+	defer unregister()
+
+	if err = srv.Serve(sock); err != nil && !errors.Is(err, net.ErrClosed) {
+		return fmt.Errorf("serve: %w", err)
 	}
 
-	return err
+	return nil
 }
 
 func (c *CLI) startSMTPServer(ctx context.Context) (net.Listener, *smtp.Server, error) {

cmd/pw/main.go

@@ -8,8 +8,10 @@ package main
 import (
 	"context"
 	"fmt"
+	"os/signal"
 	"runtime"
 	"strings"
+	"syscall"
 
 	"github.com/alecthomas/kong"
 
@@ -63,7 +65,8 @@ func main() {
 		k.Stderr = log.ErrLogger().Writer()
 	}
 
-	ctx := context.Background()
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
 	ctx = pw.WithConfig(ctx, &cli.Config)
 	ctx = pw.WithVersion(ctx, Version)