Before Connect + Before Subscribe help required (#6793)

* Before Connect + Before Subscribe #1

* Cleanup and Documentation

* Add E2E tests

* Bump parse to 2.15.0

Co-authored-by: Diamond Lewis <findlewis@gmail.com>

package-lock.json

@@ -10028,31 +10028,31 @@
       }
     },
     "parse": {
-      "version": "2.14.0",
+      "version": "2.15.0",
-      "resolved": "https://registry.npmjs.org/parse/-/parse-2.14.0.tgz",
+      "resolved": "https://registry.npmjs.org/parse/-/parse-2.15.0.tgz",
-      "integrity": "sha512-S4bbF80Aom/xDk4YNkzZG1xBHYbiFQGueJWyO4DpYlajfkEs3gp0oszFDnGadTARyCgoQGxNE4Qkege/QqNETA==",
+      "integrity": "sha512-Aupg+qd6I4X5uTacpsxROg5GlhkVn2+qOHtyOhlGj/Woi75c5cPD8kn7qhhLKcVVpe2L+HoJ+yGkMdI8IjKBKA==",
       "requires": {
-        "@babel/runtime": "7.10.2",
+        "@babel/runtime": "7.10.3",
-        "@babel/runtime-corejs3": "7.10.2",
+        "@babel/runtime-corejs3": "7.10.3",
         "crypto-js": "4.0.0",
         "react-native-crypto-js": "1.0.0",
-        "uuid": "3.3.3",
+        "uuid": "3.4.0",
         "ws": "7.3.0",
         "xmlhttprequest": "1.8.0"
       },
       "dependencies": {
         "@babel/runtime": {
-          "version": "7.10.2",
+          "version": "7.10.3",
-          "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.10.2.tgz",
+          "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.10.3.tgz",
-          "integrity": "sha512-6sF3uQw2ivImfVIl62RZ7MXhO2tap69WeWK57vAaimT6AZbE4FbqjdEJIN1UqoD6wI6B+1n9UiagafH1sxjOtg==",
+          "integrity": "sha512-RzGO0RLSdokm9Ipe/YD+7ww8X2Ro79qiXZF3HU9ljrM+qnJmH1Vqth+hbiQZy761LnMJTMitHDuKVYTk3k4dLw==",
           "requires": {
             "regenerator-runtime": "^0.13.4"
           }
         },
         "@babel/runtime-corejs3": {
-          "version": "7.10.2",
+          "version": "7.10.3",
-          "resolved": "https://registry.npmjs.org/@babel/runtime-corejs3/-/runtime-corejs3-7.10.2.tgz",
+          "resolved": "https://registry.npmjs.org/@babel/runtime-corejs3/-/runtime-corejs3-7.10.3.tgz",
-          "integrity": "sha512-+a2M/u7r15o3dV1NEizr9bRi+KUVnrs/qYxF0Z06DAPx/4VCWaz1WA7EcbE+uqGgt39lp5akWGmHsTseIkHkHg==",
+          "integrity": "sha512-HA7RPj5xvJxQl429r5Cxr2trJwOfPjKiqhCXcdQPSqO2G0RHPZpXu4fkYmBaTKCp2c/jRaMK9GB/lN+7zvvFPw==",
           "requires": {
             "core-js-pure": "^3.0.0",
             "regenerator-runtime": "^0.13.4"
@@ -10064,9 +10064,9 @@
           "integrity": "sha512-ZS5w8CpKFinUzOwW3c83oPeVXoNsrLsaCoLtJvAClH135j/R77RuymhiSErhm2lKcwSCIpmvIWSbDkIfAqKQlA=="
         },
         "uuid": {
-          "version": "3.3.3",
+          "version": "3.4.0",
-          "resolved": "https://registry.npmjs.org/uuid/-/uuid-3.3.3.tgz",
+          "resolved": "https://registry.npmjs.org/uuid/-/uuid-3.4.0.tgz",
-          "integrity": "sha512-pW0No1RGHgzlpHJO1nsVrHKpOEIxkGg1xB+v0ZmdNH5OAeAwzAVrCnI2/6Mtx+Uys6iaylxa+D3g4j63IKKjSQ=="
+          "integrity": "sha512-HjSDRw6gZE5JMggctHBcjVak08+KEVhSIiDzFnT9S9aegmp85S/bReBVTb4QTFaRNptJ9kuYaNhnbNEOkbKb/A=="
         }
       }
     },

package.json

@@ -46,7 +46,7 @@
     "lru-cache": "5.1.1",
     "mime": "2.4.6",
     "mongodb": "3.5.9",
-    "parse": "2.14.0",
+    "parse": "2.15.0",
     "pg-promise": "10.5.7",
     "pluralize": "8.0.0",
     "redis": "3.0.2",
@@ -104,6 +104,7 @@
     "posttest": "cross-env MONGODB_VERSION=${MONGODB_VERSION:=4.0.4} MONGODB_TOPOLOGY=${MONGODB_TOPOLOGY:=standalone} MONGODB_STORAGE_ENGINE=${MONGODB_STORAGE_ENGINE:=mmapv1} mongodb-runner stop",
     "coverage": "cross-env MONGODB_VERSION=${MONGODB_VERSION:=4.0.4} MONGODB_TOPOLOGY=${MONGODB_TOPOLOGY:=standalone} MONGODB_STORAGE_ENGINE=${MONGODB_STORAGE_ENGINE:=mmapv1} TESTING=1 nyc jasmine",
     "start": "node ./bin/parse-server",
+    "prettier": "prettier --write {src,spec}/**/*.js",
     "prepare": "npm run build",
     "postinstall": "node -p 'require(\"./postinstall.js\")()'"
   },

spec/ParseLiveQuery.spec.js

@@ -24,6 +24,97 @@ describe('ParseLiveQuery', function() {
     await object.save();
   });
 
+  it('can handle beforeConnect / beforeSubscribe hooks', async done => {
+    await reconfigureServer({
+      liveQuery: {
+        classNames: ['TestObject'],
+      },
+      startLiveQueryServer: true,
+      verbose: false,
+      silent: true,
+    });
+    const object = new TestObject();
+    await object.save();
+
+    Parse.Cloud.beforeSubscribe('TestObject', req => {
+      expect(req.op).toBe('subscribe');
+      expect(req.requestId).toBe(1);
+      expect(req.query).toBeDefined();
+      expect(req.user).toBeUndefined();
+    });
+
+    Parse.Cloud.beforeConnect(req => {
+      expect(req.event).toBe('connect');
+      expect(req.clients).toBe(0);
+      expect(req.subscriptions).toBe(0);
+      expect(req.useMasterKey).toBe(false);
+      expect(req.installationId).toBeDefined();
+      expect(req.user).toBeUndefined();
+      expect(req.sessionToken).toBeUndefined();
+      expect(req.client).toBeDefined();
+    });
+    const query = new Parse.Query(TestObject);
+    query.equalTo('objectId', object.id);
+    const subscription = await query.subscribe();
+    subscription.on('update', async object => {
+      expect(object.get('foo')).toBe('bar');
+      done();
+    });
+    object.set({ foo: 'bar' });
+    await object.save();
+  });
+
+  it('can handle beforeConnect error', async done => {
+    await reconfigureServer({
+      liveQuery: {
+        classNames: ['TestObject'],
+      },
+      startLiveQueryServer: true,
+      verbose: false,
+      silent: true,
+    });
+    const object = new TestObject();
+    await object.save();
+
+    Parse.Cloud.beforeConnect(() => {
+      throw new Error('You shall not pass!');
+    });
+    Parse.LiveQuery.on('error', error => {
+      expect(error).toBe('You shall not pass!');
+      done();
+    });
+    const query = new Parse.Query(TestObject);
+    query.equalTo('objectId', object.id);
+    await query.subscribe();
+  });
+
+  it('can handle beforeSubscribe error', async done => {
+    await reconfigureServer({
+      liveQuery: {
+        classNames: ['TestObject'],
+      },
+      startLiveQueryServer: true,
+      verbose: false,
+      silent: true,
+    });
+    const object = new TestObject();
+    await object.save();
+
+    Parse.Cloud.beforeSubscribe(TestObject, () => {
+      throw new Error('You shall not subscribe!');
+    });
+    Parse.LiveQuery.on('error', error => {
+      expect(error).toBe('You shall not subscribe!');
+    });
+    const query = new Parse.Query(TestObject);
+    query.equalTo('objectId', object.id);
+    const subscription = await query.subscribe();
+    subscription.on('error', error => {
+      expect(error).toBe('You shall not subscribe!');
+      done();
+    });
+  });
+
   it('handle invalid websocket payload length', async done => {
     await reconfigureServer({
       liveQuery: {

spec/ParseLiveQueryServer.spec.js

@@ -285,7 +285,7 @@ describe('ParseLiveQueryServer', function() {
       .catch(done.fail);
   });
 
-  it('can handle connect command', function() {
+  it('can handle connect command', async () => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     const parseWebSocket = {
       clientId: -1,
@@ -293,7 +293,7 @@ describe('ParseLiveQueryServer', function() {
     parseLiveQueryServer._validateKeys = jasmine
       .createSpy('validateKeys')
       .and.returnValue(true);
-    parseLiveQueryServer._handleConnect(parseWebSocket, {
+    await parseLiveQueryServer._handleConnect(parseWebSocket, {
       sessionToken: 'token',
     });
 
@@ -307,16 +307,62 @@ describe('ParseLiveQueryServer', function() {
     expect(client.pushConnect).toHaveBeenCalled();
   });
 
-  it('can handle subscribe command without clientId', function() {
+  it('basic beforeConnect rejection', async () => {
+    Parse.Cloud.beforeConnect(function () {
+      throw new Error('You shall not pass!');
+    });
+    const parseLiveQueryServer = new ParseLiveQueryServer({});
+    const parseWebSocket = {
+      clientId: -1,
+    };
+    await parseLiveQueryServer._handleConnect(parseWebSocket, {
+      sessionToken: 'token',
+    });
+    expect(parseLiveQueryServer.clients.size).toBe(0);
+    const Client = require('../lib/LiveQuery/Client').Client;
+    expect(Client.pushError).toHaveBeenCalled();
+  });
+
+  it('basic beforeSubscribe rejection', async () => {
+    Parse.Cloud.beforeSubscribe('test', function () {
+      throw new Error('You shall not pass!');
+    });
+    const parseLiveQueryServer = new ParseLiveQueryServer({});
+    const parseWebSocket = {
+      clientId: -1,
+    };
+    await parseLiveQueryServer._handleConnect(parseWebSocket, {
+      sessionToken: 'token',
+    });
+    const query = {
+      className: 'test',
+      where: {
+        key: 'value',
+      },
+      fields: ['test'],
+    };
+    const requestId = 2;
+    const request = {
+      query: query,
+      requestId: requestId,
+      sessionToken: 'sessionToken',
+    };
+    await parseLiveQueryServer._handleSubscribe(parseWebSocket, request);
+    expect(parseLiveQueryServer.clients.size).toBe(1);
+    const Client = require('../lib/LiveQuery/Client').Client;
+    expect(Client.pushError).toHaveBeenCalled();
+  });
+
+  it('can handle subscribe command without clientId', async () => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     const incompleteParseConn = {};
-    parseLiveQueryServer._handleSubscribe(incompleteParseConn, {});
+    await parseLiveQueryServer._handleSubscribe(incompleteParseConn, {});
 
     const Client = require('../lib/LiveQuery/Client').Client;
     expect(Client.pushError).toHaveBeenCalled();
   });
 
-  it('can handle subscribe command with new query', function() {
+  it('can handle subscribe command with new query', async () => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Add mock client
     const clientId = 1;
@@ -338,7 +384,7 @@ describe('ParseLiveQueryServer', function() {
       requestId: requestId,
       sessionToken: 'sessionToken',
     };
-    parseLiveQueryServer._handleSubscribe(parseWebSocket, request);
+    await parseLiveQueryServer._handleSubscribe(parseWebSocket, request);
 
     // Make sure we add the subscription to the server
     const subscriptions = parseLiveQueryServer.subscriptions;
@@ -363,7 +409,7 @@ describe('ParseLiveQueryServer', function() {
     expect(client.pushSubscribe).toHaveBeenCalledWith(requestId);
   });
 
-  it('can handle subscribe command with existing query', function() {
+  it('can handle subscribe command with existing query', async () => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Add two mock clients
     const clientId = 1;
@@ -382,7 +428,7 @@ describe('ParseLiveQueryServer', function() {
       },
       fields: ['test'],
     };
-    addMockSubscription(
+    await addMockSubscription(
       parseLiveQueryServer,
       clientId,
       requestId,
@@ -401,7 +447,7 @@ describe('ParseLiveQueryServer', function() {
       fields: ['testAgain'],
     };
     const requestIdAgain = 1;
-    addMockSubscription(
+    await addMockSubscription(
       parseLiveQueryServer,
       clientIdAgain,
       requestIdAgain,
@@ -447,7 +493,7 @@ describe('ParseLiveQueryServer', function() {
     expect(Client.pushError).toHaveBeenCalled();
   });
 
-  it('can handle unsubscribe command without not existed query', function() {
+  it('can handle unsubscribe command without not existed query', async () => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Add mock client
     const clientId = 1;
@@ -462,7 +508,7 @@ describe('ParseLiveQueryServer', function() {
     expect(Client.pushError).toHaveBeenCalled();
   });
 
-  it('can handle unsubscribe command', function() {
+  it('can handle unsubscribe command', async () => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Add mock client
     const clientId = 1;
@@ -472,7 +518,7 @@ describe('ParseLiveQueryServer', function() {
       clientId: 1,
     };
     const requestId = 2;
-    const subscription = addMockSubscription(
+    const subscription = await addMockSubscription(
       parseLiveQueryServer,
       clientId,
       requestId,
@@ -696,7 +742,7 @@ describe('ParseLiveQueryServer', function() {
     parseLiveQueryServer._onAfterDelete(message, {});
   });
 
-  it('can handle object delete command which does not match any subscription', function() {
+  it('can handle object delete command which does not match any subscription', async () => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Make deletedParseObject
     const parseObject = new Parse.Object(testClassName);
@@ -714,7 +760,7 @@ describe('ParseLiveQueryServer', function() {
     addMockClient(parseLiveQueryServer, clientId);
     // Add mock subscription
     const requestId = 2;
-    addMockSubscription(parseLiveQueryServer, clientId, requestId);
+    await addMockSubscription(parseLiveQueryServer, clientId, requestId);
     const client = parseLiveQueryServer.clients.get(clientId);
     // Mock _matchesSubscription to return not matching
     parseLiveQueryServer._matchesSubscription = function () {
@@ -729,7 +775,7 @@ describe('ParseLiveQueryServer', function() {
     expect(client.pushDelete).not.toHaveBeenCalled();
   });
 
-  it('can handle object delete command which matches some subscriptions', function(done) {
+  it('can handle object delete command which matches some subscriptions', async done => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Make deletedParseObject
     const parseObject = new Parse.Object(testClassName);
@@ -746,7 +792,7 @@ describe('ParseLiveQueryServer', function() {
     addMockClient(parseLiveQueryServer, clientId);
     // Add mock subscription
     const requestId = 2;
-    addMockSubscription(parseLiveQueryServer, clientId, requestId);
+    await addMockSubscription(parseLiveQueryServer, clientId, requestId);
     const client = parseLiveQueryServer.clients.get(clientId);
     // Mock _matchesSubscription to return matching
     parseLiveQueryServer._matchesSubscription = function () {
@@ -765,7 +811,7 @@ describe('ParseLiveQueryServer', function() {
     }, jasmine.ASYNC_TEST_WAIT_TIME);
   });
 
-  it('has no subscription and can handle object save command', function() {
+  it('has no subscription and can handle object save command', async () => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Make mock request message
     const message = generateMockMessage();
@@ -773,7 +819,7 @@ describe('ParseLiveQueryServer', function() {
     parseLiveQueryServer._onAfterSave(message);
   });
 
-  it('can handle object save command which does not match any subscription', function(done) {
+  it('can handle object save command which does not match any subscription', async done => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Make mock request message
     const message = generateMockMessage();
@@ -782,7 +828,7 @@ describe('ParseLiveQueryServer', function() {
     const client = addMockClient(parseLiveQueryServer, clientId);
     // Add mock subscription
     const requestId = 2;
-    addMockSubscription(parseLiveQueryServer, clientId, requestId);
+    await addMockSubscription(parseLiveQueryServer, clientId, requestId);
     // Mock _matchesSubscription to return not matching
     parseLiveQueryServer._matchesSubscription = function () {
       return false;
@@ -804,7 +850,7 @@ describe('ParseLiveQueryServer', function() {
     }, jasmine.ASYNC_TEST_WAIT_TIME);
   });
 
-  it('can handle object enter command which matches some subscriptions', function(done) {
+  it('can handle object enter command which matches some subscriptions', async done => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Make mock request message
     const message = generateMockMessage(true);
@@ -813,7 +859,7 @@ describe('ParseLiveQueryServer', function() {
     const client = addMockClient(parseLiveQueryServer, clientId);
     // Add mock subscription
     const requestId = 2;
-    addMockSubscription(parseLiveQueryServer, clientId, requestId);
+    await addMockSubscription(parseLiveQueryServer, clientId, requestId);
     // Mock _matchesSubscription to return matching
     // In order to mimic a enter, we need original match return false
     // and the current match return true
@@ -841,7 +887,7 @@ describe('ParseLiveQueryServer', function() {
     }, jasmine.ASYNC_TEST_WAIT_TIME);
   });
 
-  it('can handle object update command which matches some subscriptions', function(done) {
+  it('can handle object update command which matches some subscriptions', async done => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Make mock request message
     const message = generateMockMessage(true);
@@ -850,7 +896,7 @@ describe('ParseLiveQueryServer', function() {
     const client = addMockClient(parseLiveQueryServer, clientId);
     // Add mock subscription
     const requestId = 2;
-    addMockSubscription(parseLiveQueryServer, clientId, requestId);
+    await addMockSubscription(parseLiveQueryServer, clientId, requestId);
     // Mock _matchesSubscription to return matching
     parseLiveQueryServer._matchesSubscription = function (parseObject) {
       if (!parseObject) {
@@ -874,7 +920,7 @@ describe('ParseLiveQueryServer', function() {
     }, jasmine.ASYNC_TEST_WAIT_TIME);
   });
 
-  it('can handle object leave command which matches some subscriptions', function(done) {
+  it('can handle object leave command which matches some subscriptions', async done => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Make mock request message
     const message = generateMockMessage(true);
@@ -883,7 +929,7 @@ describe('ParseLiveQueryServer', function() {
     const client = addMockClient(parseLiveQueryServer, clientId);
     // Add mock subscription
     const requestId = 2;
-    addMockSubscription(parseLiveQueryServer, clientId, requestId);
+    await addMockSubscription(parseLiveQueryServer, clientId, requestId);
     // Mock _matchesSubscription to return matching
     // In order to mimic a leave, we need original match return true
     // and the current match return false
@@ -911,7 +957,7 @@ describe('ParseLiveQueryServer', function() {
     }, jasmine.ASYNC_TEST_WAIT_TIME);
   });
 
-  it('can handle update command with original object', function(done) {
+  it('can handle update command with original object', async done => {
     jasmine.restoreLibrary('../lib/LiveQuery/Client', 'Client');
     const Client = require('../lib/LiveQuery/Client').Client;
     const parseLiveQueryServer = new ParseLiveQueryServer({});
@@ -930,7 +976,7 @@ describe('ParseLiveQueryServer', function() {
     // Add mock subscription
     const requestId = 2;
 
-    addMockSubscription(
+    await addMockSubscription(
       parseLiveQueryServer,
       clientId,
       requestId,
@@ -961,7 +1007,7 @@ describe('ParseLiveQueryServer', function() {
     }, jasmine.ASYNC_TEST_WAIT_TIME);
   });
 
-  it('can handle object create command which matches some subscriptions', function(done) {
+  it('can handle object create command which matches some subscriptions', async done => {
     const parseLiveQueryServer = new ParseLiveQueryServer({});
     // Make mock request message
     const message = generateMockMessage();
@@ -970,7 +1016,7 @@ describe('ParseLiveQueryServer', function() {
     const client = addMockClient(parseLiveQueryServer, clientId);
     // Add mock subscription
     const requestId = 2;
-    addMockSubscription(parseLiveQueryServer, clientId, requestId);
+    await addMockSubscription(parseLiveQueryServer, clientId, requestId);
     // Mock _matchesSubscription to return matching
     parseLiveQueryServer._matchesSubscription = function (parseObject) {
       if (!parseObject) {
@@ -994,7 +1040,7 @@ describe('ParseLiveQueryServer', function() {
     }, jasmine.ASYNC_TEST_WAIT_TIME);
   });
 
-  it('can handle create command with fields', function(done) {
+  it('can handle create command with fields', async done => {
     jasmine.restoreLibrary('../lib/LiveQuery/Client', 'Client');
     const Client = require('../lib/LiveQuery/Client').Client;
     const parseLiveQueryServer = new ParseLiveQueryServer({});
@@ -1019,7 +1065,7 @@ describe('ParseLiveQueryServer', function() {
       },
       fields: ['test'],
     };
-    addMockSubscription(
+    await addMockSubscription(
       parseLiveQueryServer,
       clientId,
       requestId,
@@ -1842,7 +1888,7 @@ describe('ParseLiveQueryServer', function() {
     return client;
   }
 
-  function addMockSubscription(
+  async function addMockSubscription(
     parseLiveQueryServer,
     clientId,
     requestId,
@@ -1870,7 +1916,7 @@ describe('ParseLiveQueryServer', function() {
       requestId: requestId,
       sessionToken: 'sessionToken',
     };
-    parseLiveQueryServer._handleSubscribe(parseWebSocket, request);
+    await parseLiveQueryServer._handleSubscribe(parseWebSocket, request);
 
     // Make mock subscription
     const subscription = parseLiveQueryServer.subscriptions

src/LiveQuery/Client.js

@@ -62,15 +62,17 @@ class Client {
     parseWebSocket: any,
     code: number,
     error: string,
-    reconnect: boolean = true
+    reconnect: boolean = true,
+    requestId: number | void = null
   ): void {
     Client.pushResponse(
       parseWebSocket,
       JSON.stringify({
         op: 'error',
-        error: error,
+        error,
-        code: code,
+        code,
-        reconnect: reconnect,
+        reconnect,
+        requestId,
       })
     );
   }

src/LiveQuery/ParseLiveQueryServer.js

@@ -10,7 +10,11 @@ import { ParsePubSub } from './ParsePubSub';
 import SchemaController from '../Controllers/SchemaController';
 import _ from 'lodash';
 import { v4 as uuidv4 } from 'uuid';
-import { runLiveQueryEventHandlers } from '../triggers';
+import {
+  runLiveQueryEventHandlers,
+  maybeRunConnectTrigger,
+  maybeRunSubscribeTrigger,
+} from '../triggers';
 import { getAuthForSessionToken, Auth } from '../Auth';
 import { getCacheController } from '../Controllers';
 import LRU from 'lru-cache';
@@ -574,7 +578,7 @@ class ParseLiveQueryServer {
     return false;
   }
 
-  _handleConnect(parseWebsocket: any, request: any): any {
+  async _handleConnect(parseWebsocket: any, request: any): any {
     if (!this._validateKeys(request, this.keyPairs)) {
       Client.pushError(parseWebsocket, 4, 'Key in request is not valid');
       logger.error('Key in request is not valid');
@@ -589,11 +593,8 @@ class ParseLiveQueryServer {
       request.sessionToken,
       request.installationId
     );
-    parseWebsocket.clientId = clientId;
+    try {
-    this.clients.set(parseWebsocket.clientId, client);
+      const req = {
-    logger.info(`Create new client: ${parseWebsocket.clientId}`);
-    client.pushConnect();
-    runLiveQueryEventHandlers({
         client,
         event: 'connect',
         clients: this.clients.size,
@@ -601,7 +602,25 @@ class ParseLiveQueryServer {
         sessionToken: request.sessionToken,
         useMasterKey: client.hasMasterKey,
         installationId: request.installationId,
-    });
+      };
+      await maybeRunConnectTrigger('beforeConnect', req);
+      parseWebsocket.clientId = clientId;
+      this.clients.set(parseWebsocket.clientId, client);
+      logger.info(`Create new client: ${parseWebsocket.clientId}`);
+      client.pushConnect();
+      runLiveQueryEventHandlers(req);
+    } catch (error) {
+      Client.pushError(
+        parseWebsocket,
+        error.code || 101,
+        error.message || error,
+        false
+      );
+      logger.error(
+        `Failed running beforeConnect for session ${request.sessionToken} with:\n Error: ` +
+          JSON.stringify(error)
+      );
+    }
   }
 
   _hasMasterKey(request: any, validKeyPairs: any): boolean {
@@ -636,7 +655,7 @@ class ParseLiveQueryServer {
     return isValid;
   }
 
-  _handleSubscribe(parseWebsocket: any, request: any): any {
+  async _handleSubscribe(parseWebsocket: any, request: any): any {
     // If we can not find this client, return error to client
     if (!Object.prototype.hasOwnProperty.call(parseWebsocket, 'clientId')) {
       Client.pushError(
@@ -650,11 +669,14 @@ class ParseLiveQueryServer {
       return;
     }
     const client = this.clients.get(parseWebsocket.clientId);
+    const className = request.query.className;
+    try {
+      await maybeRunSubscribeTrigger('beforeSubscribe', className, request);
 
       // Get subscription from subscriptions, create one if necessary
       const subscriptionHash = queryHash(request.query);
       // Add className to subscriptions if necessary
-    const className = request.query.className;
+
       if (!this.subscriptions.has(className)) {
         this.subscriptions.set(className, new Map());
       }
@@ -705,6 +727,19 @@ class ParseLiveQueryServer {
         useMasterKey: client.hasMasterKey,
         installationId: client.installationId,
       });
+    } catch (e) {
+      Client.pushError(
+        parseWebsocket,
+        e.code || 101,
+        e.message || e,
+        false,
+        request.requestId
+      );
+      logger.error(
+        `Failed running beforeSubscribe on ${className} for session ${request.sessionToken} with:\n Error: ` +
+          JSON.stringify(e)
+      );
+    }
   }
 
   _handleUpdateSubscription(parseWebsocket: any, request: any): any {

src/cloud-code/Parse.Cloud.js

@@ -453,6 +453,60 @@ ParseCloud.afterDeleteFile = function (handler) {
   );
 };
 
+/**
+ * Registers a before live query server connect function.
+ *
+ * **Available in Cloud Code only.**
+ *
+ * ```
+ * Parse.Cloud.beforeConnect(async (request) => {
+ *   // code here
+ * })
+ *```
+ *
+ * @method beforeConnect
+ * @name Parse.Cloud.beforeConnect
+ * @param {Function} func The function to before connection is made. This function can be async and should take just one parameter, {@link Parse.Cloud.ConnectTriggerRequest}.
+ */
+ParseCloud.beforeConnect = function (handler) {
+  triggers.addConnectTrigger(
+    triggers.Types.beforeConnect,
+    handler,
+    Parse.applicationId
+  );
+};
+
+/**
+ * Registers a before live query subscription function.
+ *
+ * **Available in Cloud Code only.**
+ *
+ * If you want to use beforeSubscribe for a predefined class in the Parse JavaScript SDK (e.g. {@link Parse.User}), you should pass the class itself and not the String for arg1.
+ * ```
+ * Parse.Cloud.beforeSubscribe('MyCustomClass', (request) => {
+ *   // code here
+ * })
+ *
+ * Parse.Cloud.beforeSubscribe(Parse.User, (request) => {
+ *   // code here
+ * })
+ *```
+ *
+ * @method beforeSubscribe
+ * @name Parse.Cloud.beforeSubscribe
+ * @param {(String|Parse.Object)} arg1 The Parse.Object subclass to register the before subscription function for. This can instead be a String that is the className of the subclass.
+ * @param {Function} func The function to run before a subscription. This function can be async and should take one parameter, a {@link Parse.Cloud.TriggerRequest}.
+ */
+ParseCloud.beforeSubscribe = function (parseClass, handler) {
+  var className = getClassName(parseClass);
+  triggers.addTrigger(
+    triggers.Types.beforeSubscribe,
+    className,
+    handler,
+    Parse.applicationId
+  );
+};
+
 ParseCloud.onLiveQueryEvent = function (handler) {
   triggers.addLiveQueryEventHandler(handler, Parse.applicationId);
 };
@@ -499,6 +553,16 @@ module.exports = ParseCloud;
  * @property {Object} log The current logger inside Parse Server.
  */
 
+/**
+ * @interface Parse.Cloud.ConnectTriggerRequest
+ * @property {String} installationId If set, the installationId triggering the request.
+ * @property {Boolean} useMasterKey If true, means the master key was used.
+ * @property {Parse.User} user If set, the user that made the request.
+ * @property {Integer} clients The number of clients connected.
+ * @property {Integer} subscriptions The number of subscriptions connected.
+ * @property {String} sessionToken If set, the session of the user that made the request.
+ */
+
 /**
  * @interface Parse.Cloud.BeforeFindRequest
  * @property {String} installationId If set, the installationId triggering the request.

src/triggers.js

@@ -16,9 +16,12 @@ export const Types = {
   afterSaveFile: 'afterSaveFile',
   beforeDeleteFile: 'beforeDeleteFile',
   afterDeleteFile: 'afterDeleteFile',
+  beforeConnect: 'beforeConnect',
+  beforeSubscribe: 'beforeSubscribe',
 };
 
 const FileClassName = '@File';
+const ConnectClassName = '@Connect';
 
 const baseStore = function () {
   const Validators = {};
@@ -132,6 +135,10 @@ export function addFileTrigger(type, handler, applicationId) {
   add(Category.Triggers, `${type}.${FileClassName}`, handler, applicationId);
 }
 
+export function addConnectTrigger(type, handler, applicationId) {
+  add(Category.Triggers, `${type}.${ConnectClassName}`, handler, applicationId);
+}
+
 export function addLiveQueryEventHandler(handler, applicationId) {
   applicationId = applicationId || Parse.applicationId;
   _triggerStore[applicationId] = _triggerStore[applicationId] || baseStore();
@@ -233,10 +240,12 @@ export function getRequestObject(
     request.original = originalParseObject;
   }
 
-  if (triggerType === Types.beforeSave ||
+  if (
+    triggerType === Types.beforeSave ||
     triggerType === Types.afterSave ||
     triggerType === Types.beforeDelete ||
-    triggerType === Types.afterDelete) {
+    triggerType === Types.afterDelete
+  ) {
     // Set a copy of the context on the request object.
     request.context = Object.assign({}, context);
   }
@@ -721,7 +730,12 @@ export function getRequestFileObject(triggerType, auth, fileObject, config) {
   return request;
 }
 
-export async function maybeRunFileTrigger(triggerType, fileObject, config, auth) {
+export async function maybeRunFileTrigger(
+  triggerType,
+  fileObject,
+  config,
+  auth
+) {
   const fileTrigger = getFileTrigger(triggerType, config.applicationId);
   if (typeof fileTrigger === 'function') {
     try {
@@ -737,8 +751,8 @@ export async function maybeRunFileTrigger(triggerType, fileObject, config, auth)
         'Parse.File',
         { ...fileObject.file.toJSON(), fileSize: fileObject.fileSize },
         result,
-        auth,
+        auth
-      )
+      );
       return result || fileObject;
     } catch (error) {
       logTriggerErrorBeforeHook(
@@ -746,10 +760,57 @@ export async function maybeRunFileTrigger(triggerType, fileObject, config, auth)
         'Parse.File',
         { ...fileObject.file.toJSON(), fileSize: fileObject.fileSize },
         auth,
-        error,
+        error
       );
       throw error;
     }
   }
   return fileObject;
 }
+
+export async function maybeRunConnectTrigger(triggerType, request) {
+  const trigger = getTrigger(
+    ConnectClassName,
+    triggerType,
+    Parse.applicationId
+  );
+  if (!trigger) {
+    return;
+  }
+  request.user = await userForSessionToken(request.sessionToken);
+  return trigger(request);
+}
+
+export async function maybeRunSubscribeTrigger(
+  triggerType,
+  className,
+  request
+) {
+  const trigger = getTrigger(className, triggerType, Parse.applicationId);
+  if (!trigger) {
+    return;
+  }
+  const parseQuery = new Parse.Query(className);
+  parseQuery.withJSON(request.query);
+  request.query = parseQuery;
+  request.user = await userForSessionToken(request.sessionToken);
+  return trigger(request);
+}
+
+async function userForSessionToken(sessionToken) {
+  if (!sessionToken) {
+    return;
+  }
+  const q = new Parse.Query('_Session');
+  q.equalTo('sessionToken', sessionToken);
+  const session = await q.first({ useMasterKey: true });
+  if (!session) {
+    return;
+  }
+  const user = session.get('user');
+  if (!user) {
+    return;
+  }
+  await user.fetch({ useMasterKey: true });
+  return user;
+}