feat: Add requests idempotency verification on the server side

lib/express/idempotency.js

@@ -0,0 +1,133 @@
+import log from './logger';
+import LRU from 'lru-cache';
+import { fs, util } from 'appium-support';
+import os from 'os';
+import path from 'path';
+import { EventEmitter } from 'events';
+
+
+const CACHE_SIZE = 1024;
+const IDEMPOTENT_RESPONSES = new LRU({
+  max: CACHE_SIZE,
+  dispose: (key, {response}) => {
+    if (response) {
+      fs.rimrafSync(response);
+    }
+  },
+});
+const MONITORED_METHODS = ['POST', 'PATCH'];
+const IDEMPOTENCY_KEY_HEADER = 'x-idempotency-key';
+
+process.on('exit', () => IDEMPOTENT_RESPONSES.reset());
+
+
+function cacheResponse (key, req, res) {
+  const responseStateListener = new EventEmitter();
+  IDEMPOTENT_RESPONSES.set(key, {
+    method: req.method,
+    path: req.path,
+    response: null,
+    responseStateListener,
+  });
+  const tmpFile = path.resolve(os.tmpdir(), `${util.uuidV4()}.response`);
+  const responseListener = fs.createWriteStream(tmpFile, {
+    emitClose: true,
+  });
+  const originalSocketWriter = res.socket.write.bind(res.socket);
+  const patchedWriter = (chunk, encoding, next) => {
+    responseListener.write(chunk);
+    return originalSocketWriter(chunk, encoding, next);
+  };
+  res.socket.write = patchedWriter;
+  let writeError = null;
+  let isResponseFullySent = false;
+  responseListener.once('error', (e) => {
+    writeError = e;
+  });
+  res.once('finish', () => {
+    isResponseFullySent = true;
+    responseListener.end();
+  });
+  res.once('close', () => {
+    if (!isResponseFullySent) {
+      responseListener.end();
+    }
+  });
+  responseListener.once('close', () => {
+    if (!IDEMPOTENT_RESPONSES.has(key)) {
+      const msg = `Could not cache the response identified by '${key}'. ` +
+        `Cache consistency has been damaged`;
+      log.info(msg);
+      return responseStateListener.emit('error', new Error(msg));
+    }
+    if (writeError) {
+      log.info(`Could not cache the response identified by '${key}': ${writeError.message}`);
+      IDEMPOTENT_RESPONSES.del(key);
+      return responseStateListener.emit('error', writeError);
+    }
+    if (!isResponseFullySent) {
+      const msg = `Could not cache the response identified by '${key}', ` +
+        `because it has not been completed`;
+      log.info(msg);
+      log.info('Does the client terminate connections too early?');
+      IDEMPOTENT_RESPONSES.del(key);
+      return responseStateListener.emit('error', new Error(msg));
+    }
+
+    IDEMPOTENT_RESPONSES.get(key).response = tmpFile;
+    responseStateListener.emit('ready', tmpFile);
+  });
+}
+
+async function handleIdempotency (req, res, next) {
+  const key = req.headers[IDEMPOTENCY_KEY_HEADER];
+  if (!key) {
+    return next();
+  }
+  if (!MONITORED_METHODS.includes(req.method)) {
+    // GET, DELETE, etc. requests are idempotent by default
+    // there is no need to cache them
+    return next();
+  }
+
+  log.debug(`Request idempotency key: ${key}`);
+  if (!IDEMPOTENT_RESPONSES.has(key)) {
+    cacheResponse(key, req, res);
+    return next();
+  }
+
+  const {
+    method: storedMethod,
+    path: storedPath,
+    response,
+    responseStateListener,
+  } = IDEMPOTENT_RESPONSES.get(key);
+  if (req.method !== storedMethod || req.path !== storedPath) {
+    log.warn(`Got two different requests with the same idempotency key '${key}'`);
+    log.warn('Is the client generating idempotency keys properly?');
+    return next();
+  }
+
+  const rerouteCachedResponse = async (cachedResPath) => {
+    if (!await fs.exists(cachedResPath)) {
+      IDEMPOTENT_RESPONSES.del(key);
+      log.warn(`Could not read the cached response identified by key '${key}'`);
+      log.warn('The temporary storage is not accessible anymore');
+      return next();
+    }
+    fs.createReadStream(cachedResPath).pipe(res.socket);
+  };
+
+  if (response) {
+    log.info(`The same request with the idempotency key '${key}' has been already processed`);
+    log.info(`Rerouting its response to the current request`);
+    await rerouteCachedResponse(response);
+  } else {
+    log.info(`The same request with the idempotency key '${key}' is being processed`);
+    log.info(`Waiting for the response to be rerouted to the current request`);
+    responseStateListener.once('error', () => next());
+    responseStateListener.once('ready', rerouteCachedResponse);
+  }
+}
+
+export { handleIdempotency };

lib/express/middleware.js

@@ -1,7 +1,7 @@
 import _ from 'lodash';
 import log from './logger';
 import { errors } from '../protocol';
-
+import { handleIdempotency } from './idempotency';
 
 function allowCrossDomain (req, res, next) {
   try {
@@ -87,5 +87,5 @@ function catch404Handler (req, res) {
 export {
   allowCrossDomain, fixPythonContentType, defaultToJSONContentType,
   catchAllHandler, catch404Handler, catch4XXHandler,
-  allowCrossDomainAsyncExecute,
+  allowCrossDomainAsyncExecute, handleIdempotency,
 };

lib/express/server.js

@@ -7,13 +7,17 @@ import bodyParser from 'body-parser';
 import methodOverride from 'method-override';
 import log from './logger';
 import { startLogFormatter, endLogFormatter } from './express-logging';
-import { allowCrossDomain, fixPythonContentType, defaultToJSONContentType,
-         catchAllHandler, catch404Handler, catch4XXHandler,
-         allowCrossDomainAsyncExecute} from './middleware';
+import {
+  allowCrossDomain, fixPythonContentType, defaultToJSONContentType,
+  catchAllHandler, catch404Handler, catch4XXHandler,
+  allowCrossDomainAsyncExecute, handleIdempotency,
+} from './middleware';
 import { guineaPig, guineaPigScrollable, guineaPigAppBanner, welcome, STATIC_DIR } from './static';
 import { produceError, produceCrash } from './crash';
-import { addWebSocketHandler, removeWebSocketHandler, removeAllWebSocketHandlers,
-         getWebSocketHandlers } from './websocket';
+import {
+  addWebSocketHandler, removeWebSocketHandler, removeAllWebSocketHandlers,
+  getWebSocketHandlers
+} from './websocket';
 import B from 'bluebird';
 import { DEFAULT_BASE_PATH } from '../protocol';
 
@@ -41,14 +45,12 @@ async function server (opts = {}) {
   // http.Server.close() only stops new connections, but we need to wait until
   // all connections are closed and the `close` event is emitted
   const close = httpServer.close.bind(httpServer);
-  httpServer.close = async () => {
-    return await new B((resolve, reject) => {
-      httpServer.on('close', resolve);
-      close((err) => {
-        if (err) reject(err); // eslint-disable-line curly
-      });
+  httpServer.close = async () => await new B((resolve, reject) => {
+    httpServer.on('close', resolve);
+    close((err) => {
+      if (err) reject(err); // eslint-disable-line curly
     });
-  };
+  });
 
   return await new B((resolve, reject) => {
     httpServer.on('error', (err) => {
@@ -123,6 +125,7 @@ function configureServer (app, routeConfiguringFunction, allowCors = true, baseP
   } else {
     app.use(allowCrossDomainAsyncExecute(basePath));
   }
+  app.use(handleIdempotency);
   app.use(fixPythonContentType(basePath));
   app.use(defaultToJSONContentType);
   app.use(bodyParser.urlencoded({extended: true}));

package.json

@@ -53,7 +53,7 @@
     "serve-favicon": "^2.4.5",
     "source-map-support": "^0.5.5",
     "validate.js": "^0.13.0",
-    "webdriverio": "^5.10.9",
+    "webdriverio": "^6.0.2",
     "ws": "^7.0.0"
   },
   "scripts": {

test/basedriver/driver-e2e-tests.js

@@ -53,6 +53,67 @@ function baseDriverE2ETests (DriverClass, defaultCaps = {}) {
     }
 
     describe('session handling', function () {
+      it('should handle idempotency while creating sessions', async function () {
+        const sessionIds = [];
+        let times = 0;
+        do {
+          const res = await request({
+            url: 'http://localhost:8181/wd/hub/session',
+            headers: {
+              'X-Idempotency-Key': '123456',
+            },
+            method: 'POST',
+            json: {desiredCapabilities: defaultCaps, requiredCapabilities: {}},
+            simple: false,
+            resolveWithFullResponse: true
+          });
+
+          sessionIds.push(res.body.sessionId);
+          times++;
+        } while (times < 2);
+        _.uniq(sessionIds).length.should.equal(1);
+
+        const res = await request({
+          url: `http://localhost:8181/wd/hub/session/${sessionIds[0]}`,
+          method: 'DELETE',
+          json: true,
+          simple: false,
+          resolveWithFullResponse: true
+        });
+        res.statusCode.should.equal(200);
+        res.body.status.should.equal(0);
+      });
+
+      it('should handle idempotency while creating parallel sessions', async function () {
+        const reqs = [];
+        let times = 0;
+        do {
+          reqs.push(request({
+            url: 'http://localhost:8181/wd/hub/session',
+            headers: {
+              'X-Idempotency-Key': '12345',
+            },
+            method: 'POST',
+            json: {desiredCapabilities: defaultCaps, requiredCapabilities: {}},
+            simple: false,
+            resolveWithFullResponse: true
+          }));
+          times++;
+        } while (times < 2);
+        const sessionIds = (await B.all(reqs)).map((x) => x.body.sessionId);
+        _.uniq(sessionIds).length.should.equal(1);
+
+        const res = await request({
+          url: `http://localhost:8181/wd/hub/session/${sessionIds[0]}`,
+          method: 'DELETE',
+          json: true,
+          simple: false,
+          resolveWithFullResponse: true
+        });
+        res.statusCode.should.equal(200);
+        res.body.status.should.equal(0);
+      });
+
       it('should create session and retrieve a session id, then delete it', async function () {
         let res = await request({
           url: 'http://localhost:8181/wd/hub/session',

test/express/server-specs.js

@@ -15,7 +15,7 @@ describe('server configuration', function () {
     let app = {use: sinon.spy(), all: sinon.spy()};
     let configureRoutes = () => {};
     configureServer(app, configureRoutes);
-    app.use.callCount.should.equal(15);
+    app.use.callCount.should.equal(16);
     app.all.callCount.should.equal(4);
   });