fix(NODE-3521): remove extra server selection

Author: durran

src/operations/execute_operation.ts

@@ -77,14 +77,6 @@ export function executeOperation<
   }
 
   return maybePromise(callback, cb => {
-    if (topology.shouldCheckForSessionSupport()) {
-      return topology.selectServer(ReadPreference.primaryPreferred, err => {
-        if (err) return cb(err);
-
-        executeOperation<T, TResult>(topology, operation, cb);
-      });
-    }
-
     // The driver sessions spec mandates that we implicitly create sessions for operations
     // that are not explicitly provided with a session.
     let session: ClientSession | undefined = operation.session;

src/sdam/topology.ts

@@ -630,17 +630,6 @@ export class Topology extends TypedEventEmitter<TopologyEvents> {
 
   // Sessions related methods
 
-  /**
-   * @returns Whether the topology should initiate selection to determine session support
-   */
-  shouldCheckForSessionSupport(): boolean {
-    if (this.description.type === TopologyType.Single) {
-      return !this.description.hasKnownServers;
-    }
-
-    return !this.description.hasDataBearingServers;
-  }
-
   /** Start a logical session */
   startSession(options: ClientSessionOptions, clientOptions?: MongoOptions): ClientSession {
     const session = new ClientSession(this, this.s.sessionPool, options, clientOptions);

test/unit/sdam/topology.test.js

@@ -77,80 +77,6 @@ describe('Topology (unit)', function () {
     });
   });
 
-  describe('shouldCheckForSessionSupport', function () {
-    beforeEach(function () {
-      this.sinon = sinon.createSandbox();
-
-      // these are mocks we want across all tests
-      this.sinon.stub(Server.prototype, 'requestCheck');
-      this.sinon
-        .stub(Topology.prototype, 'selectServer')
-        .callsFake(function (selector, options, callback) {
-          setTimeout(() => {
-            const server = Array.from(this.s.servers.values())[0];
-            callback(null, server);
-          }, 50);
-        });
-    });
-
-    afterEach(function () {
-      this.sinon.restore();
-    });
-
-    it('should check for sessions if connected to a single server and has no known servers', function (done) {
-      const topology = new Topology('someserver:27019');
-      this.sinon.stub(Server.prototype, 'connect').callsFake(function () {
-        this.s.state = 'connected';
-        this.emit('connect');
-      });
-
-      topology.connect(() => {
-        expect(topology.shouldCheckForSessionSupport()).to.be.true;
-        topology.close(done);
-      });
-    });
-
-    it('should not check for sessions if connected to a single server', function (done) {
-      const topology = new Topology('someserver:27019');
-      this.sinon.stub(Server.prototype, 'connect').callsFake(function () {
-        this.s.state = 'connected';
-        this.emit('connect');
-
-        setTimeout(() => {
-          this.emit(
-            'descriptionReceived',
-            new ServerDescription('someserver:27019', { ok: 1, maxWireVersion: 6 })
-          );
-        }, 20);
-      });
-
-      topology.connect(() => {
-        expect(topology.shouldCheckForSessionSupport()).to.be.false;
-        topology.close(done);
-      });
-    });
-
-    it('should check for sessions if there are no data-bearing nodes', function (done) {
-      const topology = new Topology(['mongos:27019', 'mongos:27018', 'mongos:27017'], {});
-      this.sinon.stub(Server.prototype, 'connect').callsFake(function () {
-        this.s.state = 'connected';
-        this.emit('connect');
-
-        setTimeout(() => {
-          this.emit(
-            'descriptionReceived',
-            new ServerDescription(this.name, { ok: 1, msg: 'isdbgrid', maxWireVersion: 6 })
-          );
-        }, 20);
-      });
-
-      topology.connect(() => {
-        expect(topology.shouldCheckForSessionSupport()).to.be.false;
-        topology.close(done);
-      });
-    });
-  });
-
   describe('black holes', function () {
     let mockServer;
     beforeEach(() => mock.createServer().then(server => (mockServer = server)));