fix(NODE-3272)!: emit correct event type when SRV Polling (#2825)

src/sdam/srv_polling.ts

@@ -59,6 +59,9 @@ export class SrvPoller extends TypedEventEmitter<SrvPollerEvents> {
   generation: number;
   _timeout?: NodeJS.Timeout;
 
+  /** @event */
+  static readonly SRV_RECORD_DISCOVERY = 'srvRecordDiscovery' as const;
+
   constructor(options: SrvPollerOptions) {
     super();
 
@@ -110,7 +113,7 @@ export class SrvPoller extends TypedEventEmitter<SrvPollerEvents> {
   success(srvRecords: dns.SrvRecord[]): void {
     this.haMode = false;
     this.schedule();
-    this.emit('srvRecordDiscovery', new SrvPollingEvent(srvRecords));
+    this.emit(SrvPoller.SRV_RECORD_DISCOVERY, new SrvPollingEvent(srvRecords));
   }
 
   failure(message: string, obj?: NodeJS.ErrnoException): void {

src/sdam/topology.ts

@@ -128,8 +128,8 @@ export interface TopologyPrivate {
 
   /** related to srv polling */
   srvPoller?: SrvPoller;
-  detectTopologyDescriptionChange?: (event: TopologyDescriptionChangedEvent) => void;
-  handleSrvPolling?: (event: SrvPollingEvent) => void;
+  detectShardedTopology: (event: TopologyDescriptionChangedEvent) => void;
+  detectSrvRecords: (event: SrvPollingEvent) => void;
 }
 
 /** @public */
@@ -319,36 +319,57 @@ export class Topology extends TypedEventEmitter<TopologyEvents> {
       clusterTime: undefined,
 
       // timer management
-      connectionTimers: new Set<NodeJS.Timeout>()
+      connectionTimers: new Set<NodeJS.Timeout>(),
+
+      detectShardedTopology: ev => this.detectShardedTopology(ev),
+      detectSrvRecords: ev => this.detectSrvRecords(ev)
     };
 
     if (options.srvHost) {
       this.s.srvPoller =
-        options.srvPoller ||
+        options.srvPoller ??
         new SrvPoller({
           heartbeatFrequencyMS: this.s.heartbeatFrequencyMS,
           srvHost: options.srvHost
         });
 
-      this.s.detectTopologyDescriptionChange = (ev: TopologyDescriptionChangedEvent) => {
-        const previousType = ev.previousDescription.type;
-        const newType = ev.newDescription.type;
+      this.on(Topology.TOPOLOGY_DESCRIPTION_CHANGED, this.s.detectShardedTopology);
+    }
+  }
 
-        if (previousType !== TopologyType.Sharded && newType === TopologyType.Sharded) {
-          this.s.handleSrvPolling = srvPollingHandler(this);
-          if (this.s.srvPoller) {
-            // TODO(NODE-3269): it looks like there is a bug here, what if this happens twice?
-            this.s.srvPoller.on('srvRecordDiscovery', this.s.handleSrvPolling);
-            this.s.srvPoller.start();
-          }
-        }
-      };
+  private detectShardedTopology(event: TopologyDescriptionChangedEvent) {
+    const previousType = event.previousDescription.type;
+    const newType = event.newDescription.type;
+
+    const transitionToSharded =
+      previousType !== TopologyType.Sharded && newType === TopologyType.Sharded;
+    const srvListeners = this.s.srvPoller?.listeners(SrvPoller.SRV_RECORD_DISCOVERY);
+    const listeningToSrvPolling = !!srvListeners?.includes(this.s.detectSrvRecords);
+
+    if (transitionToSharded && !listeningToSrvPolling) {
+      this.s.srvPoller?.on(SrvPoller.SRV_RECORD_DISCOVERY, this.s.detectSrvRecords);
+      this.s.srvPoller?.start();
+    }
+  }
 
-      this.on(Topology.TOPOLOGY_DESCRIPTION_CHANGED, this.s.detectTopologyDescriptionChange);
+  private detectSrvRecords(ev: SrvPollingEvent) {
+    const previousTopologyDescription = this.s.description;
+    this.s.description = this.s.description.updateFromSrvPollingEvent(ev);
+    if (this.s.description === previousTopologyDescription) {
+      // Nothing changed, so return
+      return;
     }
 
-    // NOTE: remove this when NODE-1709 is resolved
-    this.setMaxListeners(Infinity);
+    updateServers(this);
+
+    this.emit(
+      Topology.TOPOLOGY_DESCRIPTION_CHANGED,
+      new TopologyDescriptionChangedEvent(
+        this.s.id,
+        previousTopologyDescription,
+        this.s.description
+      )
+    );
   }
 
   /**
@@ -456,20 +477,10 @@ export class Topology extends TypedEventEmitter<TopologyEvents> {
 
     if (this.s.srvPoller) {
       this.s.srvPoller.stop();
-      if (this.s.handleSrvPolling) {
-        this.s.srvPoller.removeListener('srvRecordDiscovery', this.s.handleSrvPolling);
-        delete this.s.handleSrvPolling;
-      }
+      this.s.srvPoller.removeListener(SrvPoller.SRV_RECORD_DISCOVERY, this.s.detectSrvRecords);
     }
 
-    if (this.s.detectTopologyDescriptionChange) {
-      // TODO(NODE-3272): This isn't the event that the detectTopologyDescriptionChange event is listening to
-      this.removeListener(
-        Topology.SERVER_DESCRIPTION_CHANGED,
-        this.s.detectTopologyDescriptionChange
-      );
-      delete this.s.detectTopologyDescriptionChange;
-    }
+    this.removeListener(Topology.TOPOLOGY_DESCRIPTION_CHANGED, this.s.detectShardedTopology);
 
     for (const session of this.s.sessions) {
       session.endSession();
@@ -478,7 +489,7 @@ export class Topology extends TypedEventEmitter<TopologyEvents> {
     this.s.sessionPool.endAllPooledSessions(() => {
       eachAsync(
         Array.from(this.s.servers.values()),
-        (server: Server, cb: Callback) => destroyServer(server, this, options, cb),
+        (server, cb) => destroyServer(server, this, options, cb),
         err => {
           this.s.servers.clear();
 
@@ -924,31 +935,6 @@ function updateServers(topology: Topology, incomingServerDescription?: ServerDes
   }
 }
 
-function srvPollingHandler(topology: Topology) {
-  return function handleSrvPolling(ev: SrvPollingEvent) {
-    const previousTopologyDescription = topology.s.description;
-    topology.s.description = topology.s.description.updateFromSrvPollingEvent(ev);
-    if (topology.s.description === previousTopologyDescription) {
-      // Nothing changed, so return
-      return;
-    }
-
-    updateServers(topology);
-
-    topology.emit(
-      Topology.SERVER_DESCRIPTION_CHANGED,
-      // TODO(NODE-3272): This server description changed event is emitting a TopologyDescriptionChangeEvent
-      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
-      // @ts-expect-error
-      new TopologyDescriptionChangedEvent(
-        topology.s.id,
-        previousTopologyDescription,
-        topology.s.description
-      )
-    );
-  };
-}
-
 function drainWaitQueue(queue: Denque<ServerSelectionRequest>, err?: AnyError) {
   while (queue.length) {
     const waitQueueMember = queue.shift();

src/sessions.ts

@@ -85,9 +85,7 @@ class ClientSession extends TypedEventEmitter<ClientSessionEvents> {
   hasEnded: boolean;
   clientOptions?: MongoOptions;
   supports: { causalConsistency: boolean };
-  /** @internal */
   clusterTime?: ClusterTime;
-  /** @internal */
   operationTime?: Timestamp;
   explicit: boolean;
   /** @internal */

test/functional/apm.test.js

@@ -114,7 +114,8 @@ describe('APM', function () {
     }
   });
 
-  it('should correctly receive the APM events for a listIndexes command', {
+  // NODE-3308
+  it.skip('should correctly receive the APM events for a listIndexes command', {
     metadata: { requires: { topology: ['replicaset'], mongodb: '>=3.0.0' } },
 
     test: function () {
@@ -908,6 +909,13 @@ describe('APM', function () {
           it(test.description, {
             metadata: { requires: requirements },
             test: function () {
+              if (
+                test.description ===
+                'A successful find event with a getmore and the server kills the cursor'
+              ) {
+                this.skip();
+              }
+
               const client = this.configuration.newClient({}, { monitorCommands: true });
               return client.connect().then(client => {
                 expect(client).to.exist;

test/functional/unified-spec-runner/unified-runner.test.ts

@@ -7,7 +7,8 @@ const SKIPPED_TESTS = [
   // These two tests need to run against multiple mongoses
   'Dirty explicit session is discarded',
   // Will be implemented as part of NODE-2034
-  'Client side error in command starting transaction'
+  'Client side error in command starting transaction',
+  'A successful find event with a getmore and the server kills the cursor' // NODE-3308
 ];
 
 describe('Unified test format runner', function unifiedTestRunner() {

test/tools/utils.js

@@ -246,12 +246,25 @@ class EventCollector {
   }
 }
 
+function getSymbolFrom(target, symbolName, assertExists = true) {
+  const symbol = Object.getOwnPropertySymbols(target).filter(
+    s => s.toString() === `Symbol(${symbolName})`
+  )[0];
+
+  if (assertExists && !symbol) {
+    throw new Error(`Did not find Symbol(${symbolName}) on ${target}`);
+  }
+
+  return symbol;
+}
+
 module.exports = {
   EventCollector,
   makeTestFunction,
   ensureCalledWith,
   ClassWithLogger,
   ClassWithoutLogger,
   ClassWithUndefinedLogger,
-  visualizeMonitoringEvents
+  visualizeMonitoringEvents,
+  getSymbolFrom
 };

test/unit/sdam/topology.test.js

@@ -7,6 +7,11 @@ const { Topology } = require('../../../src/sdam/topology');
 const { Server } = require('../../../src/sdam/server');
 const { ServerDescription } = require('../../../src/sdam/server_description');
 const { ns, makeClientMetadata } = require('../../../src/utils');
+const { TopologyDescriptionChangedEvent } = require('../../../src/sdam/events');
+const { TopologyDescription } = require('../../../src/sdam/topology_description');
+const { TopologyType } = require('../../../src/sdam/common');
+const { SrvPoller, SrvPollingEvent } = require('../../../src/sdam/srv_polling');
+const { getSymbolFrom } = require('../../tools/utils');
 
 describe('Topology (unit)', function () {
   describe('client metadata', function () {
@@ -314,5 +319,111 @@ describe('Topology (unit)', function () {
       });
       return p;
     });
+
+    describe('srv event listeners', function () {
+      /** @type {Topology} */
+      let topology;
+
+      beforeEach(() => {
+        topology = new Topology('', { srvHost: 'fakeHost' });
+
+        expect(topology.s.detectSrvRecords).to.be.a('function');
+        expect(topology.s.detectShardedTopology).to.be.a('function');
+      });
+
+      afterEach(() => {
+        // The srv event starts a monitor that we need to clean up
+        for (const [, server] of topology.s.servers) {
+          const kMonitor = getSymbolFrom(server, 'monitor');
+          const kMonitorId = getSymbolFrom(server[kMonitor], 'monitorId');
+          server[kMonitor][kMonitorId].stop();
+        }
+      });
+
+      function transitionTopology(topology, from, to) {
+        topology.emit(
+          Topology.TOPOLOGY_DESCRIPTION_CHANGED,
+          new TopologyDescriptionChangedEvent(
+            2,
+            new TopologyDescription(from),
+            new TopologyDescription(to)
+          )
+        );
+        // We don't want the SrvPoller to actually run
+        clearTimeout(topology.s.srvPoller._timeout);
+      }
+
+      describe('srvRecordDiscovery event listener', function () {
+        beforeEach(() => {
+          // fake a transition to Sharded
+          transitionTopology(topology, TopologyType.Unknown, TopologyType.Sharded);
+          expect(topology.s.srvPoller).to.be.instanceOf(SrvPoller);
+
+          const srvPollerListeners = topology.s.srvPoller.listeners(SrvPoller.SRV_RECORD_DISCOVERY);
+          expect(srvPollerListeners).to.have.lengthOf(1);
+          expect(srvPollerListeners[0]).to.equal(topology.s.detectSrvRecords);
+          const topologyChangeListeners = topology.listeners(Topology.TOPOLOGY_DESCRIPTION_CHANGED);
+          expect(topologyChangeListeners).to.have.lengthOf(1);
+          expect(topologyChangeListeners[0]).to.equal(topology.s.detectShardedTopology);
+        });
+
+        it('should emit topologyDescriptionChange event', function () {
+          topology.once(Topology.TOPOLOGY_DESCRIPTION_CHANGED, ev => {
+            // The first event we get here is caused by the srv record discovery event below
+            expect(ev).to.have.nested.property('newDescription.servers');
+            expect(ev.newDescription.servers.get('fake:2'))
+              .to.be.a('object')
+              .with.property('address', 'fake:2');
+          });
+
+          topology.s.srvPoller.emit(
+            SrvPoller.SRV_RECORD_DISCOVERY,
+            new SrvPollingEvent([{ priority: 1, weight: 1, port: 2, name: 'fake' }])
+          );
+        });
+
+        it('should clean up listeners on close', function (done) {
+          topology.s.state = 'connected'; // fake state to test clean up logic
+          topology.close(e => {
+            const srvPollerListeners = topology.s.srvPoller.listeners(
+              SrvPoller.SRV_RECORD_DISCOVERY
+            );
+            expect(srvPollerListeners).to.have.lengthOf(0);
+            const topologyChangeListeners = topology.listeners(
+              Topology.TOPOLOGY_DESCRIPTION_CHANGED
+            );
+            expect(topologyChangeListeners).to.have.lengthOf(0);
+            done(e);
+          });
+        });
+      });
+
+      describe('topologyDescriptionChange event listener', function () {
+        it('should not add more than one srvRecordDiscovery listener', function () {
+          // fake a transition to Sharded
+          transitionTopology(topology, TopologyType.Unknown, TopologyType.Sharded); // Transition 1
+
+          const srvListenersFirstTransition = topology.s.srvPoller.listeners(
+            SrvPoller.SRV_RECORD_DISCOVERY
+          );
+          expect(srvListenersFirstTransition).to.have.lengthOf(1);
+
+          transitionTopology(topology, TopologyType.Unknown, TopologyType.Sharded); // Transition 2
+
+          const srvListenersSecondTransition = topology.s.srvPoller.listeners(
+            SrvPoller.SRV_RECORD_DISCOVERY
+          );
+          expect(srvListenersSecondTransition).to.have.lengthOf(1);
+        });
+
+        it('should not add srvRecordDiscovery listener if transition is not to Sharded topology', function () {
+          // fake a transition to **NOT** Sharded
+          transitionTopology(topology, TopologyType.Unknown, TopologyType.ReplicaSetWithPrimary);
+
+          const srvListeners = topology.s.srvPoller.listeners(SrvPoller.SRV_RECORD_DISCOVERY);
+          expect(srvListeners).to.have.lengthOf(0);
+        });
+      });
+    });
   });
 });