feat: error on invalid queue size

src/cmap/connection.ts

@@ -17,6 +17,7 @@ import {
   MongoMissingDependencyError,
   MongoNetworkError,
   MongoNetworkTimeoutError,
+  MongoRuntimeError,
   MongoServerError,
   MongoWriteConcernError
 } from '../error';
@@ -68,6 +69,8 @@ const kAutoEncrypter = Symbol('autoEncrypter');
 /** @internal */
 const kDelayedTimeoutId = Symbol('delayedTimeoutId');
 
+const INVALID_QUEUE_SIZE = 'Connection internal queue contains more than 1 operation description';
+
 /** @internal */
 export interface CommandOptions extends BSONSerializeOptions {
   command?: boolean;
@@ -374,15 +377,20 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
     if (!operationDescription && this.isMonitoringConnection) {
       // NODE-4783: How do we recover from this when the initial hello's requestId is not
       // the responseTo when hello responses have been skipped?
-      //
-      // Get the first orphaned operation description.
-      const entry = this[kQueue].entries().next();
-      if (entry) {
-        const [requestId, orphaned]: [number, OperationDescription] = entry.value;
-        // If the orphaned operation description exists then set it.
-        operationDescription = orphaned;
-        // Remove the entry with the bad request id from the queue.
-        this[kQueue].delete(requestId);
+
+      // First check if the map is of invalid size
+      if (this[kQueue].size > 1) {
+        this.onError(new MongoRuntimeError(INVALID_QUEUE_SIZE));
+      } else {
+        // Get the first orphaned operation description.
+        const entry = this[kQueue].entries().next();
+        if (entry) {
+          const [requestId, orphaned]: [number, OperationDescription] = entry.value;
+          // If the orphaned operation description exists then set it.
+          operationDescription = orphaned;
+          // Remove the entry with the bad request id from the queue.
+          this[kQueue].delete(requestId);
+        }
       }
     }
 

test/unit/cmap/connection.test.ts

@@ -1,5 +1,5 @@
 import { expect } from 'chai';
-import { EventEmitter, on } from 'events';
+import { EventEmitter, once } from 'events';
 import { Socket } from 'net';
 import * as sinon from 'sinon';
 import { Readable } from 'stream';
@@ -9,7 +9,7 @@ import { BinMsg } from '../../../src/cmap/commands';
 import { connect } from '../../../src/cmap/connect';
 import { Connection, hasSessionSupport } from '../../../src/cmap/connection';
 import { MessageStream } from '../../../src/cmap/message_stream';
-import { MongoNetworkTimeoutError } from '../../../src/error';
+import { MongoNetworkTimeoutError, MongoRuntimeError } from '../../../src/error';
 import { isHello, ns } from '../../../src/utils';
 import * as mock from '../../tools/mongodb-mock/index';
 import { generateOpMsgBuffer, getSymbolFrom } from '../../tools/utils';
@@ -172,12 +172,13 @@ describe('new Connection()', function () {
         let callbackSpy;
         const inputStream = new Readable();
         const document = { ok: 1 };
+        const last = { isWritablePrimary: true };
 
         beforeEach(function () {
           callbackSpy = sinon.spy();
           const firstHello = generateOpMsgBuffer(document);
           const secondHello = generateOpMsgBuffer(document);
-          const thirdHello = generateOpMsgBuffer(document);
+          const thirdHello = generateOpMsgBuffer(last);
           const buffer = Buffer.concat([firstHello, secondHello, thirdHello]);
 
           connection = sinon.spy(new Connection(inputStream, connectionOptionsDefaults));
@@ -199,9 +200,10 @@ describe('new Connection()', function () {
           inputStream.push(null);
         });
 
-        it('calls the operation description callback with the document', async function () {
-          await on(inputStream, 'message');
-          expect(callbackSpy).to.be.calledOnceWith(undefined, document);
+        it('calls the callback with the last hello document', async function () {
+          const messages = await once(connection, 'message');
+          expect(messages[0].responseTo).to.equal(0);
+          expect(callbackSpy).to.be.calledOnceWith(undefined, last);
         });
       });
 
@@ -230,8 +232,8 @@ describe('new Connection()', function () {
           const msg = generateOpMsgBuffer(document);
           const msgHeader: MessageHeader = {
             length: msg.readInt32LE(0),
-            requestId: msg.readInt32LE(4),
-            responseTo: msg.readInt32LE(8),
+            requestId: 1,
+            responseTo: 0, // This will not match.
             opCode: msg.readInt32LE(12)
           };
           const msgBody = msg.subarray(16);
@@ -284,6 +286,58 @@ describe('new Connection()', function () {
           expect(callbackSpy).to.be.calledOnceWith(undefined, document);
         });
       });
+
+      context('when more than one operation description is in the queue', function () {
+        let spyOne;
+        let spyTwo;
+        const document = { ok: 1 };
+
+        beforeEach(function () {
+          spyOne = sinon.spy();
+          spyTwo = sinon.spy();
+
+          // @ts-expect-error: driverSocket does not fully satisfy the stream type, but that's okay
+          connection = sinon.spy(new Connection(driverSocket, connectionOptionsDefaults));
+          connection.isMonitoringConnection = true;
+          const queueSymbol = getSymbolFrom(connection, 'queue');
+          queue = connection[queueSymbol];
+
+          // Create the operation descriptions.
+          const descriptionOne: OperationDescription = {
+            requestId: 1,
+            cb: spyOne
+          };
+          const descriptionTwo: OperationDescription = {
+            requestId: 2,
+            cb: spyTwo
+          };
+
+          // Stick an operation description in the queue.
+          queue.set(2, descriptionOne);
+          queue.set(3, descriptionTwo);
+          // Emit a message that matches the existing operation description.
+          const msg = generateOpMsgBuffer(document);
+          const msgHeader: MessageHeader = {
+            length: msg.readInt32LE(0),
+            requestId: 2,
+            responseTo: 1,
+            opCode: msg.readInt32LE(12)
+          };
+          const msgBody = msg.subarray(16);
+
+          const message = new BinMsg(msg, msgHeader, msgBody);
+          connection.onMessage(message);
+        });
+
+        it('calls all operation description callbacks with an error', function () {
+          expect(spyOne).to.be.calledOnce;
+          expect(spyTwo).to.be.calledOnce;
+          const errorOne = spyOne.firstCall.args[0];
+          const errorTwo = spyTwo.firstCall.args[0];
+          expect(errorOne).to.be.instanceof(MongoRuntimeError);
+          expect(errorTwo).to.be.instanceof(MongoRuntimeError);
+        });
+      });
     });
   });