fix(NODE-7455): clear timeout on retry in server selection

Author: tadjik1

src/sdam/topology.ts

@@ -596,6 +596,9 @@ export class Topology extends TypedEventEmitter<TopologyEvents> {
         );
       }
       if (options.timeoutContext?.clearServerSelectionTimeout) timeout?.clear();
+      // if (!options.timeoutContext || options.timeoutContext.clearServerSelectionTimeout) {
+      //   timeout?.clear();
+      // }
       return transaction.server;
     }
 
@@ -667,6 +670,9 @@ export class Topology extends TypedEventEmitter<TopologyEvents> {
     } finally {
       abortListener?.[kDispose]();
       if (options.timeoutContext?.clearServerSelectionTimeout) timeout?.clear();
+      // if (!options.timeoutContext || options.timeoutContext.clearServerSelectionTimeout) {
+      //   timeout?.clear();
+      // }
     }
   }
   /**

test/integration/server-selection/server_selection_timeout_cleanup.test.ts

@@ -0,0 +1,83 @@
+import { expect } from 'chai';
+import * as process from 'process';
+import { setTimeout } from 'timers/promises';
+
+import { type Collection, type MongoClient } from '../../mongodb';
+
+describe.only('server selection timeout cleanup', function () {
+  let client: MongoClient;
+  let collection: Collection;
+  let utilClients: MongoClient[];
+
+  describe(
+    'timeout cleanup on retries',
+    { requires: { topology: 'sharded', mongodb: '>=4.4' } },
+    function () {
+      beforeEach(async function () {
+        client = this.configuration.newClient({ serverSelectionTimeoutMS: 500, retryWrites: true });
+        await client.connect();
+
+        collection = client.db('server_selection').collection('timeout_cleanup');
+
+        // we need to configure failpoint for every mongos as we don't know where the session will be pinned to
+        const seeds = client.topology.s.seedlist.map(address => address.toString());
+        for (const seed of seeds) {
+          const c = this.configuration.newClient(`mongodb://${seed}`, {
+            directConnection: true
+          });
+          await c.connect();
+          await c.db('admin').command({
+            configureFailPoint: 'failCommand',
+            mode: { times: 1 },
+            data: {
+              failCommands: ['insert'],
+              errorCode: 6,
+              errorsLabels: ['RetryableWriteError'],
+              closeConnection: false
+            }
+          });
+          utilClients.push(c);
+        }
+      });
+
+      afterEach(async function () {
+        for (const c of utilClients) {
+          await c.db('admin').command({
+            configureFailPoint: 'failCommand',
+            mode: 'off',
+            data: {
+              failCommands: ['insert'],
+              errorCode: 6,
+              errorsLabels: ['RetryableWriteError'],
+              closeConnection: false
+            }
+          });
+          await c.close();
+        }
+        await client.close();
+      });
+
+      it('does not leak timeout when retrying inside a sharded transaction', async function () {
+        const unhandlerRejections = [];
+        const handler = reason => unhandlerRejections.push(reason);
+        process.on('unhandledRejection', handler);
+
+        try {
+          const session = client.startSession();
+          try {
+            session.startTransaction();
+            await collection.find({}, { session }).toArray();
+            await collection.insertOne({ foo: 'bar' }, { session });
+            await session.commitTransaction();
+          } finally {
+            await session.endSession();
+          }
+          await setTimeout(1000);
+          expect(unhandlerRejections.length).to.have.lengthOf(0);
+        } finally {
+          process.removeListener('unhandledRejection', handler);
+        }
+      });
+    }
+  );
+});