fix(NODE-5064): consolidate connection cleanup logic and ensure socket is always closed

src/cmap/connection.ts

@@ -154,8 +154,8 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
   address: string;
   socketTimeoutMS: number;
   monitorCommands: boolean;
+  /** Indicates that the connection (including underlying TCP socket) has been closed. */
   closed: boolean;
-  destroyed: boolean;
   lastHelloMS?: number;
   serverApi?: ServerApi;
   helloOk?: boolean;
@@ -204,7 +204,6 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
     this.monitorCommands = options.monitorCommands;
     this.serverApi = options.serverApi;
     this.closed = false;
-    this.destroyed = false;
     this[kHello] = null;
     this[kClusterTime] = null;
 
@@ -294,56 +293,19 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
   }
 
   onError(error: Error) {
-    if (this.closed) {
-      return;
-    }
-
-    this[kStream].destroy(error);
-
-    this.closed = true;
-
-    for (const op of this[kQueue].values()) {
-      op.cb(error);
-    }
-
-    this[kQueue].clear();
-    this.emit(Connection.CLOSE);
+    this.cleanup(true, error);
   }
 
   onClose() {
-    if (this.closed) {
-      return;
-    }
-
-    this.closed = true;
-
     const message = `connection ${this.id} to ${this.address} closed`;
-    for (const op of this[kQueue].values()) {
-      op.cb(new MongoNetworkError(message));
-    }
-
-    this[kQueue].clear();
-    this.emit(Connection.CLOSE);
+    this.cleanup(true, new MongoNetworkError(message));
   }
 
   onTimeout() {
-    if (this.closed) {
-      return;
-    }
-
     this[kDelayedTimeoutId] = setTimeout(() => {
-      this[kStream].destroy();
-
-      this.closed = true;
-
       const message = `connection ${this.id} to ${this.address} timed out`;
       const beforeHandshake = this.hello == null;
-      for (const op of this[kQueue].values()) {
-        op.cb(new MongoNetworkTimeoutError(message, { beforeHandshake }));
-      }
-
-      this[kQueue].clear();
-      this.emit(Connection.CLOSE);
+      this.cleanup(true, new MongoNetworkTimeoutError(message, { beforeHandshake }));
     }, 1).unref(); // No need for this timer to hold the event loop open
   }
 
@@ -364,7 +326,7 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
 
       // First check if the map is of invalid size
       if (this[kQueue].size > 1) {
-        this.onError(new MongoRuntimeError(INVALID_QUEUE_SIZE));
+        this.cleanup(true, new MongoRuntimeError(INVALID_QUEUE_SIZE));
       } else {
         // Get the first orphaned operation description.
         const entry = this[kQueue].entries().next();
@@ -444,34 +406,67 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
   }
 
   destroy(options: DestroyOptions, callback?: Callback): void {
+    if (this.closed) {
+      process.nextTick(() => callback?.());
+      return;
+    }
+    if (typeof callback === 'function') {
+      this.once('close', () => process.nextTick(() => callback()));
+    }
+
+    // load balanced mode requires that these listeners remain on the connection
+    // after cleanup on timeouts, errors or close so we remove them before calling
+    // cleanup.
     this.removeAllListeners(Connection.PINNED);
     this.removeAllListeners(Connection.UNPINNED);
+    const message = `connection ${this.id} to ${this.address} closed`;
+    this.cleanup(options.force, new MongoNetworkError(message));
+  }
 
-    if (this[kStream] == null || this.destroyed) {
-      this.destroyed = true;
-      if (typeof callback === 'function') {
-        callback();
-      }
-
+  /**
+   * A method that cleans up the connection.  When `force` is true, this method
+   * forcibly destroys the socket.
+   *
+   * If an error is provided, any in-flight operations will be closed with the error.
+   *
+   * This method does nothing if the connection is already closed.
+   */
+  private cleanup(force: boolean, error?: Error): void {
+    if (this.closed) {
       return;
     }
 
-    if (options.force) {
-      this[kStream].destroy();
-      this.destroyed = true;
-      if (typeof callback === 'function') {
-        callback();
+    this.closed = true;
+
+    const completeCleanup = () => {
+      for (const op of this[kQueue].values()) {
+        op.cb(error);
       }
 
+      this[kQueue].clear();
+
+      this.emit(Connection.CLOSE);
+    };
+
+    this[kStream].removeAllListeners();
+    this[kMessageStream].removeAllListeners();
+
+    this[kMessageStream].destroy();
+
+    if (force) {
+      this[kStream].destroy();
+      completeCleanup();
       return;
     }
 
-    this[kStream].end(() => {
-      this.destroyed = true;
-      if (typeof callback === 'function') {
-        callback();
-      }
-    });
+    if (!this[kStream].writableEnded) {
+      this[kStream].end(() => {
+        this[kStream].destroy();
+        completeCleanup();
+      });
+    } else {
+      completeCleanup();
+    }
   }
 
   command(