fix(NODE-5749): RTTPinger always sends legacy hello (#3921)

Author: nbbeeken

src/sdam/monitor.ts

@@ -27,8 +27,6 @@ const kConnection = Symbol('connection');
 /** @internal */
 const kCancellationToken = Symbol('cancellationToken');
 /** @internal */
-const kRTTPinger = Symbol('rttPinger');
-/** @internal */
 const kRoundTripTime = Symbol('roundTripTime');
 
 const STATE_IDLE = 'idle';
@@ -100,7 +98,7 @@ export class Monitor extends TypedEventEmitter<MonitorEvents> {
   [kCancellationToken]: CancellationToken;
   /** @internal */
   [kMonitorId]?: MonitorInterval;
-  [kRTTPinger]?: RTTPinger;
+  rttPinger?: RTTPinger;
 
   get connection(): Connection | undefined {
     return this[kConnection];
@@ -219,8 +217,8 @@ function resetMonitorState(monitor: Monitor) {
   monitor[kMonitorId]?.stop();
   monitor[kMonitorId] = undefined;
 
-  monitor[kRTTPinger]?.close();
-  monitor[kRTTPinger] = undefined;
+  monitor.rttPinger?.close();
+  monitor.rttPinger = undefined;
 
   monitor[kCancellationToken].emit('cancel');
 
@@ -294,8 +292,8 @@ function checkServer(monitor: Monitor, callback: Callback<Document | null>) {
         }
       : { socketTimeoutMS: connectTimeoutMS };
 
-    if (isAwaitable && monitor[kRTTPinger] == null) {
-      monitor[kRTTPinger] = new RTTPinger(
+    if (isAwaitable && monitor.rttPinger == null) {
+      monitor.rttPinger = new RTTPinger(
         monitor[kCancellationToken],
         Object.assign(
           { heartbeatFrequencyMS: monitor.options.heartbeatFrequencyMS },
@@ -314,9 +312,10 @@ function checkServer(monitor: Monitor, callback: Callback<Document | null>) {
         hello.isWritablePrimary = hello[LEGACY_HELLO_COMMAND];
       }
 
-      const rttPinger = monitor[kRTTPinger];
       const duration =
-        isAwaitable && rttPinger ? rttPinger.roundTripTime : calculateDurationInMs(start);
+        isAwaitable && monitor.rttPinger
+          ? monitor.rttPinger.roundTripTime
+          : calculateDurationInMs(start);
 
       monitor.emit(
         Server.SERVER_HEARTBEAT_SUCCEEDED,
@@ -332,8 +331,8 @@ function checkServer(monitor: Monitor, callback: Callback<Document | null>) {
         );
         start = now();
       } else {
-        monitor[kRTTPinger]?.close();
-        monitor[kRTTPinger] = undefined;
+        monitor.rttPinger?.close();
+        monitor.rttPinger = undefined;
 
         callback(undefined, hello);
       }
@@ -430,8 +429,7 @@ export interface RTTPingerOptions extends ConnectionOptions {
 
 /** @internal */
 export class RTTPinger {
-  /** @internal */
-  [kConnection]?: Connection;
+  connection?: Connection;
   /** @internal */
   [kCancellationToken]: CancellationToken;
   /** @internal */
@@ -441,7 +439,7 @@ export class RTTPinger {
   closed: boolean;
 
   constructor(cancellationToken: CancellationToken, options: RTTPingerOptions) {
-    this[kConnection] = undefined;
+    this.connection = undefined;
     this[kCancellationToken] = cancellationToken;
     this[kRoundTripTime] = 0;
     this.closed = false;
@@ -458,8 +456,8 @@ export class RTTPinger {
     this.closed = true;
     clearTimeout(this[kMonitorId]);
 
-    this[kConnection]?.destroy({ force: true });
-    this[kConnection] = undefined;
+    this.connection?.destroy({ force: true });
+    this.connection = undefined;
   }
 }
 
@@ -478,8 +476,8 @@ function measureRoundTripTime(rttPinger: RTTPinger, options: RTTPingerOptions) {
       return;
     }
 
-    if (rttPinger[kConnection] == null) {
-      rttPinger[kConnection] = conn;
+    if (rttPinger.connection == null) {
+      rttPinger.connection = conn;
     }
 
     rttPinger[kRoundTripTime] = calculateDurationInMs(start);
@@ -489,11 +487,11 @@ function measureRoundTripTime(rttPinger: RTTPinger, options: RTTPingerOptions) {
     );
   }
 
-  const connection = rttPinger[kConnection];
+  const connection = rttPinger.connection;
   if (connection == null) {
     connect(options, (err, conn) => {
       if (err) {
-        rttPinger[kConnection] = undefined;
+        rttPinger.connection = undefined;
         rttPinger[kRoundTripTime] = 0;
         return;
       }
@@ -504,15 +502,17 @@ function measureRoundTripTime(rttPinger: RTTPinger, options: RTTPingerOptions) {
     return;
   }
 
-  connection.command(ns('admin.$cmd'), { [LEGACY_HELLO_COMMAND]: 1 }, undefined, err => {
-    if (err) {
-      rttPinger[kConnection] = undefined;
+  const commandName =
+    connection.serverApi?.version || connection.helloOk ? 'hello' : LEGACY_HELLO_COMMAND;
+  connection.commandAsync(ns('admin.$cmd'), { [commandName]: 1 }, undefined).then(
+    () => measureAndReschedule(),
+    () => {
+      rttPinger.connection?.destroy({ force: true });
+      rttPinger.connection = undefined;
       rttPinger[kRoundTripTime] = 0;
       return;
     }
-
-    measureAndReschedule();
-  });
+  );
 }
 
 /**

src/sdam/server.ts

@@ -74,9 +74,6 @@ const stateTransition = makeStateMachine({
   [STATE_CLOSING]: [STATE_CLOSING, STATE_CLOSED]
 });
 
-/** @internal */
-const kMonitor = Symbol('monitor');
-
 /** @internal */
 export type ServerOptions = Omit<ConnectionPoolOptions, 'id' | 'generation' | 'hostAddress'> &
   MonitorOptions;
@@ -119,7 +116,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
   serverApi?: ServerApi;
   hello?: Document;
   commandAsync: (ns: MongoDBNamespace, cmd: Document, options: CommandOptions) => Promise<Document>;
-  [kMonitor]: Monitor | null;
+  monitor: Monitor | null;
 
   /** @event */
   static readonly SERVER_HEARTBEAT_STARTED = SERVER_HEARTBEAT_STARTED;
@@ -175,22 +172,20 @@ export class Server extends TypedEventEmitter<ServerEvents> {
     });
 
     if (this.loadBalanced) {
-      this[kMonitor] = null;
+      this.monitor = null;
       // monitoring is disabled in load balancing mode
       return;
     }
 
     // create the monitor
-    // TODO(NODE-4144): Remove new variable for type narrowing
-    const monitor = new Monitor(this, this.s.options);
-    this[kMonitor] = monitor;
+    this.monitor = new Monitor(this, this.s.options);
 
     for (const event of HEARTBEAT_EVENTS) {
-      monitor.on(event, (e: any) => this.emit(event, e));
+      this.monitor.on(event, (e: any) => this.emit(event, e));
     }
 
-    monitor.on('resetServer', (error: MongoError) => markServerUnknown(this, error));
-    monitor.on(Server.SERVER_HEARTBEAT_SUCCEEDED, (event: ServerHeartbeatSucceededEvent) => {
+    this.monitor.on('resetServer', (error: MongoError) => markServerUnknown(this, error));
+    this.monitor.on(Server.SERVER_HEARTBEAT_SUCCEEDED, (event: ServerHeartbeatSucceededEvent) => {
       this.emit(
         Server.DESCRIPTION_RECEIVED,
         new ServerDescription(this.description.hostAddress, event.reply, {
@@ -246,7 +241,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
     // a load balancer. It never transitions out of this state and
     // has no monitor.
     if (!this.loadBalanced) {
-      this[kMonitor]?.connect();
+      this.monitor?.connect();
     } else {
       stateTransition(this, STATE_CONNECTED);
       this.emit(Server.CONNECT, this);
@@ -272,7 +267,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
     stateTransition(this, STATE_CLOSING);
 
     if (!this.loadBalanced) {
-      this[kMonitor]?.close();
+      this.monitor?.close();
     }
 
     this.pool.close(options, err => {
@@ -290,7 +285,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
    */
   requestCheck(): void {
     if (!this.loadBalanced) {
-      this[kMonitor]?.requestCheck();
+      this.monitor?.requestCheck();
     }
   }
 
@@ -465,7 +460,7 @@ function markServerUnknown(server: Server, error?: MongoServerError) {
   }
 
   if (error instanceof MongoNetworkError && !(error instanceof MongoNetworkTimeoutError)) {
-    server[kMonitor]?.reset();
+    server.monitor?.reset();
   }
 
   server.emit(