Stop timer when command exits in WaitTimeout (#6296)

internal/internal.go

@@ -237,6 +237,7 @@ func WaitTimeout(c *exec.Cmd, timeout time.Duration) error {
 
 	err := c.Wait()
 	if err == nil {
+		timer.Stop()
 		return nil
 	}
 

internal/internal_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"compress/gzip"
 	"io/ioutil"
+	"log"
 	"os/exec"
 	"testing"
 	"time"
@@ -64,6 +65,30 @@ func TestRunTimeout(t *testing.T) {
 	assert.True(t, elapsed < time.Millisecond*75)
 }
 
+// Verifies behavior of a command that doesn't get killed.
+func TestRunTimeoutFastExit(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping test due to random failures.")
+	}
+	if echobin == "" {
+		t.Skip("'echo' binary not available on OS, skipping.")
+	}
+	cmd := exec.Command(echobin)
+	start := time.Now()
+	err := RunTimeout(cmd, time.Millisecond*20)
+	buf := &bytes.Buffer{}
+	log.SetOutput(buf)
+	elapsed := time.Since(start)
+
+	require.NoError(t, err)
+	// Verify that command gets killed in 20ms, with some breathing room
+	assert.True(t, elapsed < time.Millisecond*75)
+
+	// Verify "process already finished" log doesn't occur.
+	time.Sleep(time.Millisecond * 75)
+	require.Equal(t, "", buf.String())
+}
+
 func TestCombinedOutputTimeout(t *testing.T) {
 	// TODO: Fix this test
 	t.Skip("Test failing too often, skip for now and revisit later.")