test: cli force exit signal handler

Signed-off-by: Alano Terblanche <18033717+Benehiko@users.noreply.github.com>

cmd/docker/docker.go

@@ -326,23 +326,23 @@ func tryPluginRun(ctx context.Context, dockerCli command.Cli, cmd *cobra.Command
 	return nil
 }
 
-// registerForceExitGoroutine registers a goroutine that will force exit the
-// process after 3 SIGTERM/SIGINT signals.
-func registerForceExitGoroutine(ctx context.Context, w io.Writer) {
-	// setup a signal handler to force exit after 3 SIGTERM/SIGINT
-	go func() {
+// forceExitAfter3TerminationSignals waits for the first termination signal
+// to be caught and the context to be marked as done, then registers a new
+// signal handler for subsequent signals. It forces the process to exit
+// after 3 SIGTERM/SIGINT signals.
+func forceExitAfter3TerminationSignals(ctx context.Context, w io.Writer) {
+	// wait for the first signal to be caught and the context to be marked as done
 	<-ctx.Done()
+	// register a new signal handler for subsequent signals
 	sig := make(chan os.Signal, 2)
 	signal.Notify(sig, platformsignals.TerminationSignals...)
-		count := 0
-		for range sig {
-			count++
-			if count >= 2 {
+
+	// once we have received a total of 3 signals we force exit the cli
+	for i := 0; i < 2; i++ {
+		<-sig
+	}
 	_, _ = fmt.Fprint(w, "\ngot 3 SIGTERM/SIGINTs, forcefully exiting\n")
 	os.Exit(1)
-			}
-		}
-	}()
 }
 
 //nolint:gocyclo
@@ -406,7 +406,7 @@ func runDocker(ctx context.Context, dockerCli *command.DockerCli) error {
 
 	// This is a fallback for the case where the command does not exit
 	// based on context cancellation.
-	registerForceExitGoroutine(ctx, dockerCli.Err())
+	go forceExitAfter3TerminationSignals(ctx, dockerCli.Err())
 
 	// We've parsed global args already, so reset args to those
 	// which remain.

cmd/docker/docker_test.go

@@ -1,17 +1,28 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
 	"context"
+	"fmt"
 	"io"
 	"os"
+	"os/exec"
+	"os/signal"
+	"strings"
+	"syscall"
 	"testing"
+	"time"
 
 	"github.com/docker/cli/cli/command"
 	"github.com/docker/cli/cli/debug"
+	"github.com/docker/cli/cli/streams"
+	"github.com/docker/cli/cmd/docker/internal/signals"
 	"github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
 	"gotest.tools/v3/assert"
 	is "gotest.tools/v3/assert/cmp"
+	"gotest.tools/v3/poll"
 )
 
 func TestClientDebugEnabled(t *testing.T) {
@@ -75,3 +86,92 @@ func TestVersion(t *testing.T) {
 	assert.NilError(t, err)
 	assert.Check(t, is.Contains(b.String(), "Docker version"))
 }
+
+func TestFallbackForceExit(t *testing.T) {
+	longRunningCommand := cobra.Command{
+		RunE: func(cmd *cobra.Command, args []string) error {
+			read, _, err := os.Pipe()
+			if err != nil {
+				return err
+			}
+
+			// wait until the parent process sends a signal to exit
+			_, _, err = bufio.NewReader(read).ReadLine()
+			return err
+		},
+	}
+
+	// This is the child process that will run the long running command
+	if os.Getenv("TEST_FALLBACK_FORCE_EXIT") == "1" {
+		fmt.Println("running long command")
+		ctx, cancel := signal.NotifyContext(context.Background(), signals.TerminationSignals...)
+		t.Cleanup(cancel)
+
+		longRunningCommand.SetErr(streams.NewOut(os.Stderr))
+		longRunningCommand.SetOut(streams.NewOut(os.Stdout))
+
+		go forceExitAfter3TerminationSignals(ctx, streams.NewOut(os.Stderr))
+
+		err := longRunningCommand.ExecuteContext(ctx)
+		if err != nil {
+			os.Exit(0)
+		}
+		return
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	t.Cleanup(cancel)
+
+	// spawn the child process
+	cmd := exec.CommandContext(ctx, os.Args[0], "-test.run=TestFallbackForceExit")
+	cmd.Env = append(os.Environ(), "TEST_FALLBACK_FORCE_EXIT=1")
+
+	var buf strings.Builder
+	cmd.Stderr = &buf
+	cmd.Stdout = &buf
+
+	t.Cleanup(func() {
+		_ = cmd.Process.Kill()
+	})
+
+	assert.NilError(t, cmd.Start())
+
+	poll.WaitOn(t, func(t poll.LogT) poll.Result {
+		if strings.Contains(buf.String(), "running long command") {
+			return poll.Success()
+		}
+		return poll.Continue("waiting for child process to start")
+	}, poll.WithTimeout(1*time.Second), poll.WithDelay(100*time.Millisecond))
+
+	for i := 0; i < 3; i++ {
+		cmd.Process.Signal(syscall.SIGINT)
+		time.Sleep(100 * time.Millisecond)
+	}
+
+	cmdErr := make(chan error, 1)
+	go func() {
+		cmdErr <- cmd.Wait()
+	}()
+
+	poll.WaitOn(t, func(t poll.LogT) poll.Result {
+		if strings.Contains(buf.String(), "got 3 SIGTERM/SIGINTs, forcefully exiting") {
+			return poll.Success()
+		}
+		return poll.Continue("waiting for child process to exit")
+	},
+		poll.WithTimeout(1*time.Second), poll.WithDelay(100*time.Millisecond))
+
+	select {
+	case cmdErr := <-cmdErr:
+		assert.Error(t, cmdErr, "exit status 1")
+		exitErr, ok := cmdErr.(*exec.ExitError)
+		if !ok {
+			t.Fatalf("unexpected error type: %T", cmdErr)
+		}
+		if exitErr.Success() {
+			t.Fatalf("unexpected exit status: %v", exitErr)
+		}
+	case <-time.After(1 * time.Second):
+		t.Fatal("timed out waiting for child process to exit")
+	}
+}