refactor(db)!: suppress Db events (#2251)

Db class no longer emits events, only MongoClient does now. Also removed parent/child relationships for databases.

NODE-1709

Author: emadum

lib/db.js

@@ -1,7 +1,6 @@
 'use strict';
 
-const EventEmitter = require('events');
-const { inherits, deprecate } = require('util');
+const { deprecate } = require('util');
 const { AggregationCursor, CommandCursor } = require('./cursor');
 const { ObjectID } = require('./utils').retrieveBSON();
 const ReadPreference = require('./read_preference');
@@ -26,7 +25,6 @@ const {
 
 // Operations
 const {
-  createListener,
   ensureIndex,
   evaluate,
   profilingInfo,
@@ -88,7 +86,6 @@ const legalOptionNames = [
   'readConcern',
   'retryMiliSeconds',
   'numberOfRetries',
-  'parentDb',
   'noListener',
   'loggerLevel',
   'logger',
@@ -130,18 +127,11 @@ const legalOptionNames = [
  * @property {boolean} slaveOk The current slaveOk value for the db instance.
  * @property {object} writeConcern The current write concern values.
  * @property {object} topology Access the topology object (single server, replicaset or mongos).
- * @fires Db#close
- * @fires Db#reconnect
- * @fires Db#error
- * @fires Db#timeout
- * @fires Db#parseError
- * @fires Db#fullsetup
  * @return {Db} a Db instance.
  */
 function Db(databaseName, topology, options) {
   options = options || {};
   if (!(this instanceof Db)) return new Db(databaseName, topology, options);
-  EventEmitter.call(this);
 
   // Get the promiseLibrary
   const promiseLibrary = options.promiseLibrary || Promise;
@@ -156,8 +146,6 @@ function Db(databaseName, topology, options) {
   this.s = {
     // DbCache
     dbCache: {},
-    // Children db's
-    children: [],
     // Topology
     topology: topology,
     // Options
@@ -170,8 +158,6 @@ function Db(databaseName, topology, options) {
     readPreference: ReadPreference.fromOptions(options),
     // Set buffermaxEntries
     bufferMaxEntries: typeof options.bufferMaxEntries === 'number' ? options.bufferMaxEntries : -1,
-    // Parent db (if chained)
-    parentDb: options.parentDb || null,
     // Set up the primary key factory or fallback to ObjectID
     pkFactory: options.pkFactory || ObjectID,
     // Get native parser
@@ -195,23 +181,9 @@ function Db(databaseName, topology, options) {
   getSingleProperty(this, 'bufferMaxEntries', this.s.bufferMaxEntries);
   getSingleProperty(this, 'databaseName', this.s.namespace.db);
 
-  // This is a child db, do not register any listeners
-  if (options.parentDb) return;
   if (this.s.noListener) return;
-
-  // Add listeners
-  topology.on('error', createListener(this, 'error', this));
-  topology.on('timeout', createListener(this, 'timeout', this));
-  topology.on('close', createListener(this, 'close', this));
-  topology.on('parseError', createListener(this, 'parseError', this));
-  topology.once('open', createListener(this, 'open', this));
-  topology.once('fullsetup', createListener(this, 'fullsetup', this));
-  topology.once('all', createListener(this, 'all', this));
-  topology.on('reconnect', createListener(this, 'reconnect', this));
 }
 
-inherits(Db, EventEmitter);
-
 // Topology
 Object.defineProperty(Db.prototype, 'topology', {
   enumerable: true,
@@ -789,11 +761,6 @@ Db.prototype.ensureIndex = deprecate(function(name, fieldOrSpec, options, callba
   ]);
 }, 'Db.ensureIndex is deprecated as of MongoDB version 3.0 / driver version 2.0');
 
-Db.prototype.addChild = function(db) {
-  if (this.s.parentDb) return this.s.parentDb.addChild(db);
-  this.s.children.push(db);
-};
-
 /**
  * Add a user to the database.
  * @method
@@ -963,64 +930,6 @@ Db.prototype.getLogger = function() {
   return this.s.logger;
 };
 
-/**
- * Db close event
- *
- * Emitted after a socket closed against a single server or mongos proxy.
- *
- * @event Db#close
- * @type {MongoError}
- */
-
-/**
- * Db reconnect event
- *
- *  * Server: Emitted when the driver has reconnected and re-authenticated.
- *  * ReplicaSet: N/A
- *  * Mongos: Emitted when the driver reconnects and re-authenticates successfully against a Mongos.
- *
- * @event Db#reconnect
- * @type {object}
- */
-
-/**
- * Db error event
- *
- * Emitted after an error occurred against a single server or mongos proxy.
- *
- * @event Db#error
- * @type {MongoError}
- */
-
-/**
- * Db timeout event
- *
- * Emitted after a socket timeout occurred against a single server or mongos proxy.
- *
- * @event Db#timeout
- * @type {MongoError}
- */
-
-/**
- * Db parseError event
- *
- * The parseError event is emitted if the driver detects illegal or corrupt BSON being received from the server.
- *
- * @event Db#parseError
- * @type {MongoError}
- */
-
-/**
- * Db fullsetup event, emitted when all servers in the topology have been connected to at start up time.
- *
- * * Server: Emitted when the driver has connected to the single server and has authenticated.
- * * ReplSet: Emitted after the driver has attempted to connect to all replicaset members.
- * * Mongos: Emitted after the driver has attempted to connect to all mongos proxies.
- *
- * @event Db#fullsetup
- * @type {Db}
- */
-
 // Constants
 Db.SYSTEM_NAMESPACE_COLLECTION = CONSTANTS.SYSTEM_NAMESPACE_COLLECTION;
 Db.SYSTEM_INDEX_COLLECTION = CONSTANTS.SYSTEM_INDEX_COLLECTION;

lib/mongo_client.js

@@ -6,7 +6,6 @@ const ChangeStream = require('./change_stream');
 const ReadPreference = require('./read_preference');
 const { MongoError } = require('./error');
 const WriteConcern = require('./write_concern');
-const NativeTopology = require('./topologies/native_topology');
 const { maybePromise, MongoDBNamespace } = require('./utils');
 const { inherits, deprecate } = require('util');
 const { connect, validOptions } = require('./operations/connect');
@@ -241,40 +240,26 @@ MongoClient.prototype.close = function(force, callback) {
 
   const client = this;
   return maybePromise(callback, cb => {
-    const completeClose = err => {
-      client.emit('close', client);
-
-      if (!(client.topology instanceof NativeTopology)) {
-        for (const item of client.s.dbCache) {
-          item[1].emit('close', client);
-        }
-      }
-
-      client.removeAllListeners('close');
-      cb(err);
-    };
-
     if (client.topology == null) {
-      completeClose();
+      cb();
       return;
     }
 
     client.topology.close(force, err => {
       const autoEncrypter = client.topology.s.options.autoEncrypter;
       if (!autoEncrypter) {
-        completeClose(err);
+        cb(err);
         return;
       }
 
-      autoEncrypter.teardown(force, err2 => completeClose(err || err2));
+      autoEncrypter.teardown(force, err2 => cb(err || err2));
     });
   });
 };
 
 /**
- * Create a new Db instance sharing the current socket connections. Be aware that the new db instances are
- * related in a parent-child relationship to the original instance so that events are correctly emitted on child
- * db instances. Child db instances are cached so performing db('db1') twice will return the same instance.
+ * Create a new Db instance sharing the current socket connections.
+ * Db instances are cached so performing db('db1') twice will return the same instance.
  * You can control these behaviors with the options noListener and returnNonCachedInstance.
  *
  * @method

lib/operations/command.js

@@ -28,7 +28,6 @@ const debugFields = [
   'retryMiliSeconds',
   'readPreference',
   'pkFactory',
-  'parentDb',
   'promiseLibrary',
   'noListener'
 ];

lib/operations/db_ops.js

@@ -48,7 +48,6 @@ const debugFields = [
   'retryMiliSeconds',
   'readPreference',
   'pkFactory',
-  'parentDb',
   'promiseLibrary',
   'noListener'
 ];
@@ -236,11 +235,6 @@ function createListener(db, e, object) {
   function listener(err) {
     if (object.listeners(e).length > 0) {
       object.emit(e, err, db);
-
-      // Emit on all associated db's if available
-      for (let i = 0; i < db.s.children.length; i++) {
-        db.s.children[i].emit(e, err, db.s.children[i]);
-      }
     }
   }
   return listener;

test/functional/multiple_db.test.js

@@ -7,66 +7,6 @@ describe('Multiple Databases', function() {
     return setupDatabase(this.configuration);
   });
 
-  /**
-   * @ignore
-   */
-  it('shouldCorrectlyEmitErrorOnAllDbsOnPoolClose', {
-    // Add a tag that our runner can trigger on
-    // in this case we are setting that node needs to be higher than 0.10.X to run
-    metadata: { requires: { topology: 'single' } },
-
-    // The actual test we wish to run
-    test: function(done) {
-      if (process.platform !== 'linux') {
-        var configuration = this.configuration;
-        var client = configuration.newClient({ w: 1 }, { poolSize: 1 });
-
-        // All inserted docs
-        var numberOfCloses = 0;
-
-        // Start server
-        client.on('close', function(err) {
-          test.ok(err !== null);
-          numberOfCloses = numberOfCloses + 1;
-        });
-
-        client.connect(function(err, client) {
-          var db = client.db(configuration.db);
-
-          db.createCollection('shouldCorrectlyErrorOnAllDbs', function(err, collection) {
-            test.equal(null, err);
-
-            collection.insert({ a: 1 }, { w: 1 }, function(err) {
-              test.equal(null, err);
-              // Open a second db
-              var db2 = client.db('tests_2');
-              // Add a close handler
-              db2.on('close', function(err) {
-                test.ok(err !== null);
-                numberOfCloses = numberOfCloses + 1;
-                test.equal(2, numberOfCloses);
-              });
-
-              // Open a second db
-              var db3 = client.db('tests_3');
-              // Add a close handler
-              db3.on('close', function(err) {
-                test.ok(err !== null);
-                numberOfCloses = numberOfCloses + 1;
-                test.equal(3, numberOfCloses);
-                done();
-              });
-
-              client.close();
-            });
-          });
-        });
-      } else {
-        done();
-      }
-    }
-  });
-
   /**
    * Test the auto connect functionality of the db
    *

test/functional/operation_example.test.js

@@ -3615,6 +3615,10 @@ describe('Operation Examples', function() {
     test: function(done) {
       var configuration = this.configuration;
       var client = configuration.newClient(configuration.writeConcernMax(), { poolSize: 1 });
+      // NODE-2484: investigate double close event in Unified Topology environment
+      // client.on('close', function() {
+      //   done();
+      // });
       client.connect(function(err, client) {
         // LINE var MongoClient = require('mongodb').MongoClient,
         // LINE   test = require('assert');
@@ -3626,14 +3630,9 @@ describe('Operation Examples', function() {
         // REMOVE-LINE done();
         // REMOVE-LINE var db = client.db(configuration.db);
         // BEGIN
-        var db = client.db(configuration.db);
         test.equal(null, err);
 
-        db.on('close', function() {
-          done();
-        });
-
-        client.close();
+        client.close(done);
       });
       // END
     }