fix: avoid runner output buffer race

Author: intel352

cmd/github-actions-runner-job/main.go

@@ -363,7 +363,8 @@ type runningCommand struct {
 	path   string
 	cancel context.CancelFunc
 	cmd    *exec.Cmd
-	output bytes.Buffer
+	stdout bytes.Buffer
+	stderr bytes.Buffer
 }
 
 func startCommand(ctx context.Context, path, dir string, args ...string) (*runningCommand, error) {
@@ -372,8 +373,8 @@ func startCommand(ctx context.Context, path, dir string, args ...string) (*runni
 	cmd.Dir = dir
 	cmd.Env = os.Environ()
 	running := &runningCommand{path: path, cancel: cancel, cmd: cmd}
-	cmd.Stdout = &running.output
-	cmd.Stderr = &running.output
+	cmd.Stdout = &running.stdout
+	cmd.Stderr = &running.stderr
 	if err := cmd.Start(); err != nil {
 		cancel()
 		return nil, fmt.Errorf("%s start failed: %w", filepath.Base(path), err)
@@ -385,7 +386,8 @@ func (r *runningCommand) wait() error {
 	err := r.cmd.Wait()
 	r.cancel()
 	if err != nil {
-		return fmt.Errorf("%s failed: %w: %s", filepath.Base(r.path), err, strings.TrimSpace(r.output.String()))
+		output := strings.TrimSpace(strings.Join([]string{r.stdout.String(), r.stderr.String()}, "\n"))
+		return fmt.Errorf("%s failed: %w: %s", filepath.Base(r.path), err, output)
 	}
 	return nil
 }

cmd/github-actions-runner-job/main_test.go

@@ -80,7 +80,7 @@ func TestT915CommandRunsDynamicProviderEnvelopeThroughSidecarAndRunner(t *testin
 
 	runnerDir := t.TempDir()
 	writeExecutable(t, filepath.Join(runnerDir, "config.sh"), "#!/bin/sh\nprintf '%s\\n' \"$@\" > \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/config.args\"\nprintf '{\"agentId\":42}\\n' > .runner\n")
-	writeExecutable(t, filepath.Join(runnerDir, "run.sh"), "#!/bin/sh\nprintf '%s\\n' \"$@\" > \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/run.args\"\ntouch \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/run.started\"\nwhile [ ! -f \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/dispatch.seen\" ]; do sleep 0.1; done\nprintf 'runner executed\\n' > \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/run.log\"\n")
+	writeExecutable(t, filepath.Join(runnerDir, "run.sh"), "#!/bin/sh\nprintf '%s\\n' \"$@\" > \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/run.args\"\ntouch \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/run.started\"\nwhile [ ! -f \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/dispatch.seen\" ]; do sleep 0.1; done\n(for i in $(seq 1 50); do printf 'stdout-%s\\n' \"$i\"; done) &\n(for i in $(seq 1 50); do printf 'stderr-%s\\n' \"$i\" >&2; done) &\nwait\nprintf 'runner executed\\n' > \"$GITHUB_ACTIONS_RUNNER_JOB_TEST_DIR/run.log\"\n")
 	t.Chdir(workspace)
 	t.Setenv("COMPUTE_GITHUB_RUNNER_PROVIDER_URL", sidecar.URL)
 	t.Setenv("COMPUTE_GITHUB_RUNNER_PROVIDER_TOKEN", "provider-token")