Plumb error info to X-ray (#544)

* WIP: Plumb error info to x-ray

* cleanup

* fix xrayException shape - the json tags differ from InvokeResponse_Error

* no stack should be empty list instead of nil

* gofmt

* stable order of the paths array

lambda/invoke_loop.go

@@ -104,7 +104,13 @@ func handleInvoke(invoke *invoke, handler *handlerOptions) error {
 func reportFailure(invoke *invoke, invokeErr *messages.InvokeResponse_Error) error {
 	errorPayload := safeMarshal(invokeErr)
 	log.Printf("%s", errorPayload)
-	if err := invoke.failure(bytes.NewReader(errorPayload), contentTypeJSON); err != nil {
+
+	causeForXRay, err := json.Marshal(makeXRayError(invokeErr))
+	if err != nil {
+		return fmt.Errorf("unexpected error occured when serializing the function error cause for X-Ray: %v", err)
+	}
+
+	if err := invoke.failure(bytes.NewReader(errorPayload), contentTypeJSON, causeForXRay); err != nil {
 		return fmt.Errorf("unexpected error occurred when sending the function error to the API: %v", err)
 	}
 	return nil
@@ -166,3 +172,41 @@ func safeMarshal(v interface{}) []byte {
 	}
 	return payload
 }
+
+type xrayException struct {
+	Type    string                                      `json:"type"`
+	Message string                                      `json:"message"`
+	Stack   []*messages.InvokeResponse_Error_StackFrame `json:"stack"`
+}
+
+type xrayError struct {
+	WorkingDirectory string          `json:"working_directory"`
+	Exceptions       []xrayException `json:"exceptions"`
+	Paths            []string        `json:"paths"`
+}
+
+func makeXRayError(invokeResponseError *messages.InvokeResponse_Error) *xrayError {
+	paths := make([]string, 0, len(invokeResponseError.StackTrace))
+	visitedPaths := make(map[string]struct{}, len(invokeResponseError.StackTrace))
+	for _, frame := range invokeResponseError.StackTrace {
+		if _, exists := visitedPaths[frame.Path]; !exists {
+			visitedPaths[frame.Path] = struct{}{}
+			paths = append(paths, frame.Path)
+		}
+	}
+
+	cwd, _ := os.Getwd()
+	exceptions := []xrayException{{
+		Type:    invokeResponseError.Type,
+		Message: invokeResponseError.Message,
+		Stack:   invokeResponseError.StackTrace,
+	}}
+	if exceptions[0].Stack == nil {
+		exceptions[0].Stack = []*messages.InvokeResponse_Error_StackFrame{}
+	}
+	return &xrayError{
+		WorkingDirectory: cwd,
+		Paths:            paths,
+		Exceptions:       exceptions,
+	}
+}

lambda/invoke_loop_test.go

@@ -90,6 +90,110 @@ func TestCustomErrorMarshaling(t *testing.T) {
 	}
 }
 
+func TestXRayCausePlumbing(t *testing.T) {
+	errors := []error{
+		errors.New("barf"),
+		messages.InvokeResponse_Error{
+			Type:    "yoloError",
+			Message: "hello yolo",
+			StackTrace: []*messages.InvokeResponse_Error_StackFrame{
+				{Label: "yolo", Path: "yolo", Line: 2},
+				{Label: "hi", Path: "hello/hello", Line: 12},
+			},
+		},
+		messages.InvokeResponse_Error{
+			Type:    "yoloError",
+			Message: "hello yolo",
+			StackTrace: []*messages.InvokeResponse_Error_StackFrame{
+				{Label: "hi", Path: "hello/hello", Line: 12},
+				{Label: "hihi", Path: "hello/hello", Line: 13},
+				{Label: "yolo", Path: "yolo", Line: 2},
+				{Label: "hi", Path: "hello/hello", Line: 14},
+			},
+		},
+		messages.InvokeResponse_Error{
+			Type:       "yoloError",
+			Message:    "hello yolo",
+			StackTrace: []*messages.InvokeResponse_Error_StackFrame{},
+		},
+		messages.InvokeResponse_Error{
+			Type:    "yoloError",
+			Message: "hello yolo",
+		},
+	}
+	wd, _ := os.Getwd()
+	expected := []string{
+		`{
+		    "working_directory":"` + wd + `", 
+		    "paths": [], 
+		    "exceptions": [{ 
+			"type": "errorString", 
+			"message": "barf", 
+			"stack": []
+		    }]
+		}`,
+		`{
+		    "working_directory":"` + wd + `", 
+		    "paths": ["yolo", "hello/hello"], 
+		    "exceptions": [{ 
+			"type": "yoloError", 
+			"message": "hello yolo", 
+			"stack": [
+			    {"label": "yolo", "path": "yolo", "line": 2},
+			    {"label": "hi", "path": "hello/hello", "line": 12}
+			]
+		    }]
+		}`,
+		`{
+		    "working_directory":"` + wd + `", 
+		    "paths": ["hello/hello", "yolo"],
+		    "exceptions": [{ 
+			"type": "yoloError", 
+			"message": "hello yolo", 
+			"stack": [
+			    {"label": "hi", "path": "hello/hello", "line": 12},
+			    {"label": "hihi", "path": "hello/hello", "line": 13},
+			    {"label": "yolo", "path": "yolo", "line": 2},
+			    {"label": "hi", "path": "hello/hello", "line": 14}
+			]
+		    }]
+		}`,
+		`{
+		    "working_directory":"` + wd + `", 
+		    "paths": [], 
+		    "exceptions": [{ 
+			"type": "yoloError", 
+			"message": "hello yolo", 
+			"stack": []
+		    }]
+		}`,
+		`{
+		    "working_directory":"` + wd + `", 
+		    "paths": [], 
+		    "exceptions": [{ 
+			"type": "yoloError", 
+			"message": "hello yolo", 
+			"stack": []
+		    }]
+		}`,
+	}
+	require.Equal(t, len(errors), len(expected))
+	ts, record := runtimeAPIServer(``, len(errors))
+	defer ts.Close()
+	n := 0
+	handler := NewHandler(func() error {
+		defer func() { n++ }()
+		return errors[n]
+	})
+	endpoint := strings.Split(ts.URL, "://")[1]
+	expectedError := fmt.Sprintf("failed to GET http://%s/2018-06-01/runtime/invocation/next: got unexpected status code: 410", endpoint)
+	assert.EqualError(t, startRuntimeAPILoop(endpoint, handler), expectedError)
+	for i := range errors {
+		assert.JSONEq(t, expected[i], string(record.xrayCauses[i]))
+	}
+
+}
+
 func TestRuntimeAPIContextPlumbing(t *testing.T) {
 	handler := NewHandler(func(ctx context.Context) (interface{}, error) {
 		lc, _ := lambdacontext.FromContext(ctx)
@@ -271,6 +375,7 @@ type requestRecord struct {
 	nPosts       int
 	responses    [][]byte
 	contentTypes []string
+	xrayCauses   []string
 }
 
 type eventMetadata struct {
@@ -336,6 +441,7 @@ func runtimeAPIServer(eventPayload string, failAfter int, overrides ...eventMeta
 			w.WriteHeader(http.StatusAccepted)
 			record.responses = append(record.responses, response.Bytes())
 			record.contentTypes = append(record.contentTypes, r.Header.Get("Content-Type"))
+			record.xrayCauses = append(record.xrayCauses, r.Header.Get(headerXRayErrorCause))
 		default:
 			w.WriteHeader(http.StatusBadRequest)
 		}

lambda/runtime_api_client.go

@@ -22,11 +22,13 @@ const (
 	headerCognitoIdentity    = "Lambda-Runtime-Cognito-Identity"
 	headerClientContext      = "Lambda-Runtime-Client-Context"
 	headerInvokedFunctionARN = "Lambda-Runtime-Invoked-Function-Arn"
+	headerXRayErrorCause     = "Lambda-Runtime-Function-Xray-Error-Cause"
 	trailerLambdaErrorType   = "Lambda-Runtime-Function-Error-Type"
 	trailerLambdaErrorBody   = "Lambda-Runtime-Function-Error-Body"
 	contentTypeJSON          = "application/json"
 	contentTypeBytes         = "application/octet-stream"
 	apiVersion               = "2018-06-01"
+	xrayErrorCauseMaxSize    = 1024 * 1024
 )
 
 type runtimeAPIClient struct {
@@ -57,17 +59,17 @@ type invoke struct {
 //   - An invoke is not complete until next() is called again!
 func (i *invoke) success(body io.Reader, contentType string) error {
 	url := i.client.baseURL + i.id + "/response"
-	return i.client.post(url, body, contentType)
+	return i.client.post(url, body, contentType, nil)
 }
 
 // failure sends the payload to the Runtime API. This marks the function's invoke as a failure.
 // Notes:
 //   - The execution of the function process continues, and is billed, until next() is called again!
 //   - A Lambda Function continues to be re-used for future invokes even after a failure.
 //     If the error is fatal (panic, unrecoverable state), exit the process immediately after calling failure()
-func (i *invoke) failure(body io.Reader, contentType string) error {
+func (i *invoke) failure(body io.Reader, contentType string, causeForXRay []byte) error {
 	url := i.client.baseURL + i.id + "/error"
-	return i.client.post(url, body, contentType)
+	return i.client.post(url, body, contentType, causeForXRay)
 }
 
 // next connects to the Runtime API and waits for a new invoke Request to be available.
@@ -108,7 +110,7 @@ func (c *runtimeAPIClient) next() (*invoke, error) {
 	}, nil
 }
 
-func (c *runtimeAPIClient) post(url string, body io.Reader, contentType string) error {
+func (c *runtimeAPIClient) post(url string, body io.Reader, contentType string, xrayErrorCause []byte) error {
 	b := newErrorCapturingReader(body)
 	req, err := http.NewRequest(http.MethodPost, url, b)
 	if err != nil {
@@ -118,6 +120,10 @@ func (c *runtimeAPIClient) post(url string, body io.Reader, contentType string)
 	req.Header.Set("User-Agent", c.userAgent)
 	req.Header.Set("Content-Type", contentType)
 
+	if xrayErrorCause != nil && len(xrayErrorCause) < xrayErrorCauseMaxSize {
+		req.Header.Set(headerXRayErrorCause, string(xrayErrorCause))
+	}
+
 	resp, err := c.httpClient.Do(req)
 	if err != nil {
 		return fmt.Errorf("failed to POST to %s: %v", url, err)

lambda/runtime_api_client_test.go

@@ -92,7 +92,7 @@ func TestClientDoneAndError(t *testing.T) {
 			assert.NoError(t, err)
 		})
 		t.Run(fmt.Sprintf("happy Error with payload[%d]", i), func(t *testing.T) {
-			err := invoke.failure(bytes.NewReader(payload), contentTypeJSON)
+			err := invoke.failure(bytes.NewReader(payload), contentTypeJSON, nil)
 			assert.NoError(t, err)
 		})
 	}
@@ -105,7 +105,7 @@ func TestInvalidRequestsForMalformedEndpoint(t *testing.T) {
 	require.Error(t, err)
 	err = (&invoke{client: newRuntimeAPIClient("🚨")}).success(nil, "")
 	require.Error(t, err)
-	err = (&invoke{client: newRuntimeAPIClient("🚨")}).failure(nil, "")
+	err = (&invoke{client: newRuntimeAPIClient("🚨")}).failure(nil, "", nil)
 	require.Error(t, err)
 }
 
@@ -145,7 +145,7 @@ func TestStatusCodes(t *testing.T) {
 					require.NoError(t, err)
 				})
 				t.Run("failure should not error", func(t *testing.T) {
-					err := invoke.failure(nil, "")
+					err := invoke.failure(nil, "", nil)
 					require.NoError(t, err)
 				})
 			} else {
@@ -158,7 +158,7 @@ func TestStatusCodes(t *testing.T) {
 					}
 				})
 				t.Run("failure should error", func(t *testing.T) {
-					err := invoke.failure(nil, "")
+					err := invoke.failure(nil, "", nil)
 					require.Error(t, err)
 					if i != 301 && i != 302 && i != 303 {
 						assert.Contains(t, err.Error(), "unexpected status code")