feat(createRequestHtmlFragment): implemented circuit breaker

__tests__/integration/one-app.spec.js

@@ -102,7 +102,7 @@ describe('Tests that require Docker setup', () => {
       expect(rawHeaders).not.toHaveProperty('access-control-max-age');
       expect(rawHeaders).not.toHaveProperty('access-control-allow-methods');
       expect(rawHeaders).not.toHaveProperty('access-control-allow-headers');
-      // any respnse headers
+      // any response headers
       expect(rawHeaders).not.toHaveProperty('access-control-allow-origin');
       expect(rawHeaders).not.toHaveProperty('access-control-expose-headers');
       expect(rawHeaders).not.toHaveProperty('access-control-allow-credentials');

__tests__/server/middleware/createRequestHtmlFragment.spec.js

@@ -14,24 +14,35 @@
  * permissions and limitations under the License.
  */
 
+/* global BigInt */
+
 import url from 'url';
 import { browserHistory } from '@americanexpress/one-app-router';
 import { Map as iMap, fromJS } from 'immutable';
+import { composeModules } from 'holocron';
 import match from '../../../src/universal/utils/matchPromisified';
+import breaker from '../../../src/server/utils/circuitBreaker';
 
 import * as reactRendering from '../../../src/server/utils/reactRendering';
 
 jest.mock('../../../src/universal/utils/matchPromisified');
 
 jest.mock('holocron', () => ({
   composeModules: jest.fn(() => 'composeModules'),
+  getModule: () => () => 0,
 }));
 
+const sleep = (ms) => new Promise((res) => setTimeout(res, ms));
 const renderForStringSpy = jest.spyOn(reactRendering, 'renderForString');
 const renderForStaticMarkupSpy = jest.spyOn(reactRendering, 'renderForStaticMarkup');
+const msToNs = (n) => n * 1e6;
 
 describe('createRequestHtmlFragment', () => {
   jest.spyOn(console, 'error').mockImplementation(() => {});
+  const realHrtime = process.hrtime;
+  const mockHrtime = (...args) => realHrtime(...args);
+  mockHrtime.bigint = jest.fn();
+  process.hrtime = mockHrtime;
 
   let req;
   let res;
@@ -59,6 +70,8 @@ describe('createRequestHtmlFragment', () => {
   });
 
   beforeEach(() => {
+    jest.clearAllMocks();
+    breaker.close();
     req = jest.fn();
     req.headers = {};
 
@@ -78,6 +91,10 @@ describe('createRequestHtmlFragment', () => {
     renderForStaticMarkupSpy.mockClear();
   });
 
+  afterAll(() => {
+    process.hrtime = realHrtime;
+  });
+
   it('returns a function', () => {
     const createRequestHtmlFragment = require(
       '../../../src/server/middleware/createRequestHtmlFragment'
@@ -93,7 +110,6 @@ describe('createRequestHtmlFragment', () => {
     const middleware = createRequestHtmlFragment({ createRoutes });
     return middleware(req, res, next)
       .then(() => {
-        const { composeModules } = require('holocron');
         expect(composeModules).toHaveBeenCalled();
         expect(composeModules.mock.calls[0][0]).toMatchSnapshot();
         expect(dispatch).toHaveBeenCalledWith('composeModules');
@@ -229,4 +245,86 @@ describe('createRequestHtmlFragment', () => {
     expect(next).toHaveBeenCalled();
     /* eslint-enable no-console */
   });
+
+  it('should open the circuit when event loop lag is > 30ms', async () => {
+    expect.assertions(5);
+    const createRequestHtmlFragment = require(
+      '../../../src/server/middleware/createRequestHtmlFragment'
+    ).default;
+    const middleware = createRequestHtmlFragment({ createRoutes });
+    process.hrtime.bigint
+      .mockReturnValueOnce(BigInt(msToNs(100)))
+      .mockReturnValueOnce(BigInt(msToNs(131)));
+    await sleep(110);
+    await middleware(req, res, next);
+    expect(next).toHaveBeenCalled();
+    expect(composeModules).not.toHaveBeenCalled();
+    expect(renderForStringSpy).not.toHaveBeenCalled();
+    expect(renderForStaticMarkupSpy).not.toHaveBeenCalled();
+    expect(req.appHtml).toBe('');
+  });
+
+  it('should not open the circuit when event loop lag is < 30ms', async () => {
+    expect.assertions(5);
+    const createRequestHtmlFragment = require(
+      '../../../src/server/middleware/createRequestHtmlFragment'
+    ).default;
+    const middleware = createRequestHtmlFragment({ createRoutes });
+    process.hrtime.bigint
+      .mockReturnValueOnce(BigInt(msToNs(100)))
+      .mockReturnValueOnce(BigInt(msToNs(120)));
+    await sleep(110);
+    await middleware(req, res, next);
+    expect(next).toHaveBeenCalled();
+    expect(composeModules).toHaveBeenCalled();
+    expect(renderForStringSpy).toHaveBeenCalled();
+    expect(renderForStaticMarkupSpy).not.toHaveBeenCalled();
+    expect(req.appHtml).toBe('hi');
+  });
+
+  it('should not open the circuit for partials', async () => {
+    expect.assertions(5);
+    const createRequestHtmlFragment = require(
+      '../../../src/server/middleware/createRequestHtmlFragment'
+    ).default;
+    const middleware = createRequestHtmlFragment({ createRoutes });
+    getState.mockImplementationOnce(() => fromJS({
+      rendering: {
+        renderPartialOnly: true,
+      },
+    }));
+    process.hrtime.bigint
+      .mockReturnValueOnce(BigInt(msToNs(100)))
+      .mockReturnValueOnce(BigInt(msToNs(131)));
+    await sleep(110);
+    await middleware(req, res, next);
+    expect(next).toHaveBeenCalled();
+    expect(composeModules).toHaveBeenCalled();
+    expect(renderForStringSpy).not.toHaveBeenCalled();
+    expect(renderForStaticMarkupSpy).toHaveBeenCalled();
+    expect(req.appHtml).toBe('hi');
+  });
+
+  it('should not open the when scripts are disabled', async () => {
+    expect.assertions(5);
+    const createRequestHtmlFragment = require(
+      '../../../src/server/middleware/createRequestHtmlFragment'
+    ).default;
+    const middleware = createRequestHtmlFragment({ createRoutes });
+    getState.mockImplementationOnce(() => fromJS({
+      rendering: {
+        disableScripts: true,
+      },
+    }));
+    process.hrtime.bigint
+      .mockReturnValueOnce(BigInt(msToNs(100)))
+      .mockReturnValueOnce(BigInt(msToNs(131)));
+    await sleep(110);
+    await middleware(req, res, next);
+    expect(next).toHaveBeenCalled();
+    expect(composeModules).toHaveBeenCalled();
+    expect(renderForStringSpy).not.toHaveBeenCalled();
+    expect(renderForStaticMarkupSpy).toHaveBeenCalled();
+    expect(req.appHtml).toBe('hi');
+  });
 });

__tests__/server/utils/circuitBreaker.spec.js

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2020 American Express Travel Related Services Company, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+import CircuitBreaker from 'opossum';
+import breaker, {
+  setEventLoopLagThreshold,
+  getEventLoopLagThreshold,
+} from '../../../src/server/utils/circuitBreaker';
+
+describe('Circuit breaker', () => {
+  it('should be an opossum circuit breaker', () => {
+    expect(breaker).toBeInstanceOf(CircuitBreaker);
+  });
+
+  // Tests for circuit breaker functionality can be found in
+  // __tests__/server/middleware/createRequestHtmlFragment.spec.js
+
+  describe('setEventLoopLagThreshold', () => {
+    it('should set a default value of 30ms', () => {
+      setEventLoopLagThreshold();
+      expect(getEventLoopLagThreshold()).toBe(30);
+    });
+
+    it('should set value to 30ms if input is not a number', () => {
+      setEventLoopLagThreshold('hello, world');
+      expect(getEventLoopLagThreshold()).toBe(30);
+    });
+
+    it('should set the given value', () => {
+      setEventLoopLagThreshold(44);
+      expect(getEventLoopLagThreshold()).toBe(44);
+    });
+
+    it('should handle numbers as strings', () => {
+      setEventLoopLagThreshold('55');
+      expect(getEventLoopLagThreshold()).toBe(55);
+    });
+  });
+});

__tests__/server/utils/onModuleLoad.spec.jsx

@@ -29,11 +29,12 @@ import { setCorsOrigins } from '../../../src/server/middleware/conditionallyAllo
 import { extendRestrictedAttributesAllowList, validateSafeRequestRestrictedAttributes } from '../../../src/server/utils/safeRequest';
 import { setConfigureRequestLog } from '../../../src/server/utils/logging/serverMiddleware';
 import { setCreateSsrFetch } from '../../../src/server/utils/createSsrFetch';
+import { getEventLoopLagThreshold } from '../../../src/server/utils/circuitBreaker';
 
 jest.mock('../../../src/server/utils/stateConfig', () => ({
   setStateConfig: jest.fn(),
   getClientStateConfig: jest.fn(),
-  getServerStateConfig: jest.fn(),
+  getServerStateConfig: jest.fn(() => ({ rootModuleName: 'root-module' })),
 }));
 jest.mock('@americanexpress/env-config-utils');
 jest.mock('../../../src/server/utils/readJsonFile', () => () => ({ buildVersion: '4.43.0-0-38f0178d' }));
@@ -311,6 +312,22 @@ describe('onModuleLoad', () => {
     expect(setCorsOrigins).toHaveBeenCalledWith(corsOrigins);
   });
 
+  it('sets the event loop lag threshold from the root module', () => {
+    const eventLoopLagThreshold = 50;
+    expect(getEventLoopLagThreshold()).not.toBe(eventLoopLagThreshold);
+    onModuleLoad({
+      module: {
+        [CONFIGURATION_KEY]: {
+          csp,
+          eventLoopLagThreshold,
+        },
+        [META_DATA_KEY]: { version: '1.0.14' },
+      },
+      moduleName: 'some-root',
+    });
+    expect(getEventLoopLagThreshold()).toBe(eventLoopLagThreshold);
+  });
+
   it('logs when the root module is loaded', () => {
     onModuleLoad({
       module: { [CONFIGURATION_KEY]: { csp }, [META_DATA_KEY]: { version: '1.0.15' } },

docs/api/modules/App-Configuration.md

@@ -267,6 +267,26 @@ if (!global.BROWSER) {
 }
 ```
 
+## `eventLoopLagThreshold`
+**Module Type**
+* ✅ Root Module
+* 🚫 Child Module
+
+**Shape**
+```js
+if (!global.BROWSER) {
+  Module.appConfig = {
+    eventLoopLagThreshold: Number,
+  };
+}
+```
+
+The `eventLoopLagThreshold` directive accepts a number representing the threshold of the event loop lag (in milliseconds) before opening the circuit in our circuit breaker created with [Opossum](https://nodeshift.dev/opossum/). Once the circuit is open, it will remain open for 10 seconds and close at that time pending the event loop lag. The default value is `30`. If you desire to disable the circuit completely, set this value to `Infinity`.
+
+**📘 More Information**
+* [Frank Lloyd Root's `appConfig`](../../../prod-sample/sample-modules/frank-lloyd-root/0.0.0/src/config.js)
+* Library: [Opossum](https://nodeshift.dev/opossum/)
+
 `createSsrFetch` allows for customizing the fetch client used in `one-app` to perform server-side requests.
 
 For example, you may wish to forward cookies or headers from the initial page load request to all the requisite SSR API requests.

package.json

@@ -94,6 +94,8 @@
     "ip": "^1.1.5",
     "lean-intl": "^4.2.2",
     "matcher": "^2.1.0",
+    "opossum": "^5.0.0",
+    "opossum-prometheus": "^0.1.0",
     "pidusage": "^2.0.17",
     "prom-client": "^11.5.3",
     "prometheus-gc-stats": "^0.6.2",

prod-sample/sample-modules/frank-lloyd-root/0.0.0/src/config.js

@@ -18,6 +18,7 @@ import csp from './csp';
 import createFrankLikeFetch from './createFrankLikeFetch';
 
 export default {
+  eventLoopLagThreshold: Infinity,
   csp,
   corsOrigins: [/\.example.com$/],
   configureRequestLog: ({ req, log = {} }) => {

prod-sample/sample-modules/frank-lloyd-root/0.0.1/src/components/FrankLloydRoot.jsx

@@ -48,6 +48,7 @@ FrankLloydRoot.propTypes = {
 
 if (!global.BROWSER) {
   FrankLloydRoot.appConfig = {
+    eventLoopLagThreshold: Infinity,
     // eslint-disable-next-line global-require
     csp: require('../csp').default,
     provideStateConfig: {

prod-sample/sample-modules/frank-lloyd-root/0.0.2/src/config.js

@@ -17,6 +17,7 @@
 import csp from './csp';
 
 export default {
+  eventLoopLagThreshold: Infinity,
   csp,
   extendSafeRequestRestrictedAttributes: {
     cookies: [

src/server/middleware/createRequestHtmlFragment.jsx

@@ -20,6 +20,7 @@ import url, { Url } from 'url';
 import { RouterContext } from '@americanexpress/one-app-router';
 import { composeModules } from 'holocron';
 import match from '../../universal/utils/matchPromisified';
+import breaker from '../utils/circuitBreaker';
 
 import { renderForString, renderForStaticMarkup } from '../utils/reactRendering';
 
@@ -69,11 +70,22 @@ export default function createRequestHtmlFragment({ createRoutes }) {
           },
         }));
 
-      await dispatch(composeModules(routeModules));
-
       const state = store.getState();
       const disableScripts = state.getIn(['rendering', 'disableScripts']);
       const renderPartialOnly = state.getIn(['rendering', 'renderPartialOnly']);
+
+      if (disableScripts || renderPartialOnly) {
+        await dispatch(composeModules(routeModules));
+      } else {
+        const fallback = await breaker.fire({ dispatch, modules: routeModules });
+
+        if (fallback) {
+          req.appHtml = '';
+          req.helmetInfo = {};
+          return next();
+        }
+      }
+
       const renderMethod = (disableScripts || renderPartialOnly)
         ? renderForStaticMarkup : renderForString;