Pull missing docker images automatically (#191)

Author: eseliger

cmd/src/actions_exec.go

@@ -241,8 +241,8 @@ Format of the action JSON files:
 
 		logger := newActionLogger(*verbose, *keepLogsFlag)
 
-		// Build Docker images etc.
-		err = prepareAction(ctx, action)
+		// Fetch Docker images etc.
+		err = prepareAction(ctx, action, logger)
 		if err != nil {
 			return errors.Wrap(err, "Failed to prepare action")
 		}
@@ -393,14 +393,14 @@ func validateActionDefinition(def []byte) error {
 	return errs.ErrorOrNil()
 }
 
-func prepareAction(ctx context.Context, action Action) error {
+func prepareAction(ctx context.Context, action Action, logger *actionLogger) error {
 	// Build any Docker images.
 	for _, step := range action.Steps {
 		if step.Type == "docker" {
 			// Set digests for Docker images so we don't cache action runs in 2 different images with
 			// the same tag.
 			var err error
-			step.ImageContentDigest, err = getDockerImageContentDigest(ctx, step.Image)
+			step.ImageContentDigest, err = getDockerImageContentDigest(ctx, step.Image, logger)
 			if err != nil {
 				return errors.Wrap(err, "Failed to get Docker image content digest")
 			}
@@ -417,14 +417,35 @@ func prepareAction(ctx context.Context, action Action) error {
 // have been pulled from or pushed to a registry. See
 // https://windsock.io/explaining-docker-image-ids/ under "A Final Twist" for a good
 // explanation.
-func getDockerImageContentDigest(ctx context.Context, image string) (string, error) {
+func getDockerImageContentDigest(ctx context.Context, image string, logger *actionLogger) (string, error) {
 	// TODO!(sqs): is image id the right thing to use here? it is NOT the
 	// digest. but the digest is not calculated for all images (unless they are
 	// pulled/pushed from/to a registry), see
 	// https://github.com/moby/moby/issues/32016.
 	out, err := exec.CommandContext(ctx, "docker", "image", "inspect", "--format", "{{.Id}}", "--", image).CombinedOutput()
 	if err != nil {
-		return "", fmt.Errorf("error inspecting docker image (try `docker pull %q` to fix this): %s", image, bytes.TrimSpace(out))
+		if !strings.Contains(string(out), "No such image") {
+			return "", fmt.Errorf("error inspecting docker image %q: %s", image, bytes.TrimSpace(out))
+		}
+		logger.Infof("Pulling Docker image %q...\n", image)
+		pullCmd := exec.CommandContext(ctx, "docker", "image", "pull", image)
+		prefix := fmt.Sprintf("docker image pull %s", image)
+		pullCmd.Stdout = logger.InfoPipe(prefix)
+		pullCmd.Stderr = logger.ErrorPipe(prefix)
+
+		err = pullCmd.Start()
+		if err != nil {
+			return "", fmt.Errorf("error pulling docker image %q: %s", image, err)
+		}
+		err = pullCmd.Wait()
+		if err != nil {
+			return "", fmt.Errorf("error pulling docker image %q: %s", image, err)
+		}
+	}
+	out, err = exec.CommandContext(ctx, "docker", "image", "inspect", "--format", "{{.Id}}", "--", image).CombinedOutput()
+	// This time, the image MUST be present, so the issue must be something else.
+	if err != nil {
+		return "", fmt.Errorf("error inspecting docker image %q: %s", image, bytes.TrimSpace(out))
 	}
 	id := string(bytes.TrimSpace(out))
 	if id == "" {

cmd/src/actions_exec_logger.go

@@ -150,6 +150,24 @@ func (a *actionLogger) RepoWriter(repoName string) (io.Writer, bool) {
 	return w, ok
 }
 
+func (a *actionLogger) InfoPipe(prefix string) io.Writer {
+	if !a.verbose {
+		return ioutil.Discard
+	}
+	stdoutPrefix := fmt.Sprintf("%s -> [STDOUT]: ", yellow.Sprint(prefix))
+	stderr := textio.NewPrefixWriter(os.Stderr, stdoutPrefix)
+	return io.Writer(stderr)
+}
+
+func (a *actionLogger) ErrorPipe(prefix string) io.Writer {
+	if !a.verbose {
+		return ioutil.Discard
+	}
+	stderrPrefix := fmt.Sprintf("%s -> [STDERR]: ", yellow.Sprint(prefix))
+	stderr := textio.NewPrefixWriter(os.Stderr, stderrPrefix)
+	return io.Writer(stderr)
+}
+
 func (a *actionLogger) RepoStdoutStderr(repoName string) (io.Writer, io.Writer, bool) {
 	a.mu.Lock()
 	defer a.mu.Unlock()