Fail on no entrypoint, don't crash

executor/mock/standalone/standalone_test.go

@@ -56,6 +56,10 @@ var (
 		name: "titusoss/big-image",
 		tag:  "20171025-1508900976",
 	}
+	noEntrypoint = testImage{
+		name: "titusoss/no-entrypoint-test",
+		tag:  "20171109-1510275133",
+	}
 )
 
 // This file still uses log as opposed to using the testing library's built-in logging framework.
@@ -79,6 +83,7 @@ func TestStandalone(t *testing.T) {
 		testImageNonExistingDigestFails,
 		testImagePullError,
 		testBadEntrypoint,
+		testNoEntrypoint,
 		testCanWriteInLogsAndSubDirs,
 		testShutdown,
 		testCancelPullBigImage,
@@ -478,6 +483,17 @@ func testBadEntrypoint(t *testing.T) {
 	}
 }
 
+func testNoEntrypoint(t *testing.T) {
+	ji := &mock.JobInput{
+		ImageName: noEntrypoint.name,
+		Version:   noEntrypoint.tag,
+	}
+	// We expect this to fail
+	if mock.RunJobExpectingSuccess(ji, false) {
+		t.Fail()
+	}
+}
+
 func testCanWriteInLogsAndSubDirs(t *testing.T) {
 	cmd := `sh -c "mkdir -p /logs/prana && echo begining > /logs/prana/prana.log && ` +
 		`mv /logs/prana/prana.log /logs/prana/prana-2016.log && echo ending >> /logs/out"`

executor/runtime/docker.go

@@ -97,6 +97,9 @@ var (
 // and it's a temporary measure during protocol evolution.
 var ErrMissingIAMRole = errors.New("IAM Role Missing")
 
+// NoEntrypointError indicates that the Titus job does not have an entrypoint, or command
+var NoEntrypointError = &BadEntryPointError{reason: errors.New("Image, and job have no entrypoint, or command")}
+
 // I'm sorry for using regex, it's a simple rule though
 // 1. The string must start with a-z, A-Z, or _
 // 2. The string MAY contain more characters, in the set a-z, A-Z, 0-9, or _
@@ -629,6 +632,7 @@ func (r *DockerRuntime) Prepare(parentCtx context.Context, c *Container, binds [
 	var dockerCfg *container.Config
 	var hostCfg *container.HostConfig
 	var size int64
+	var imageInfo types.ImageInspect
 
 	err := r.validateEFSMounts(c)
 	if err != nil {
@@ -640,7 +644,18 @@ func (r *DockerRuntime) Prepare(parentCtx context.Context, c *Container, binds [
 		goto error
 	}
 
-	size = r.reportDockerImageSizeMetric(c, c.QualifiedImageName())
+	imageInfo, _, err = r.client.ImageInspectWithRaw(ctx, c.QualifiedImageName())
+	if err != nil {
+		log.Errorf("Error in inspecting docker image %s: %v", c.QualifiedImageName(), err)
+		return err
+	}
+	size = r.reportDockerImageSizeMetric(c, imageInfo)
+
+	// Check if this image (container) has a an entrypoint, or if we
+	// were passed one
+	if !r.hasEntrypoint(imageInfo, c) {
+		return NoEntrypointError
+	}
 
 	dockerCfg, hostCfg, err = r.dockerConfig(c, binds, size)
 	if err != nil {
@@ -1471,17 +1486,23 @@ func (r *DockerRuntime) Cleanup(c *Container) error {
 }
 
 // reportDockerImageSizeMetric reports a metric that represents the container image's size
-func (r *DockerRuntime) reportDockerImageSizeMetric(c *Container, image string) int64 {
-	imageInfo, _, err := r.client.ImageInspectWithRaw(context.TODO(), image)
-	if err != nil {
-		log.Errorf("Error in inspecting docker image %s : %v\n", image, err)
-		return 0
-	}
+func (r *DockerRuntime) reportDockerImageSizeMetric(c *Container, imageInfo types.ImageInspect) int64 {
 	// reporting image size in KB
 	r.metrics.Gauge("titus.executor.dockerImageSize", int(imageInfo.Size/KB), c.ImageTagForMetrics())
 	return imageInfo.Size
 }
 
+func (r *DockerRuntime) hasEntrypoint(imageInfo types.ImageInspect, c *Container) bool {
+	if entrypoint, err := GetEntrypointFromProto(c.TitusInfo); err != nil {
+		// If this happens, we return true, because this error will be bubbled up elsewhere
+		return true
+	} else if entrypoint != nil {
+		return true
+	}
+
+	return imageInfo.Config.Entrypoint != nil || imageInfo.Config.Cmd != nil
+}
+
 func shouldClose(c io.Closer) {
 	if err := c.Close(); err != nil {
 		log.Error("Could not close: ", err)