mongodb/node-mongodb-native · error · MongoUnexpectedServerResponseError

Server ended moreToCome unexpectedly

Error message

Server ended moreToCome unexpectedly

What it means

A MongoUnexpectedServerResponseError thrown in Connection.exhaustCommand when the sendCommand generator ends normally (no more data) while the driver expected the server to keep sending moreToCome batches. Exhaust cursors (used by change streams and getMore-style streaming) rely on the server continuously pushing replies; a clean end signals the stream was terminated prematurely.

Solutions

1. Disable response buffering on any proxy in front of MongoDB.
2. Use resume tokens to restart the change stream after the interruption.
3. Check server logs for killCursors or cursor timeout events.
4. Ensure the connection between driver and server is not terminated by an idle-timeout device.

Example fix

// before (no resume strategy)
const cs = coll.watch();
for await (const c of cs) handle(c);

// after (resume on unexpected end)
let resumeToken;
while (true) {
  const cs = coll.watch([], { resumeAfter: resumeToken });
  try {
    for await (const c of cs) { resumeToken = c._id; handle(c); }
  } catch (e) { /* reconnect */ }
}

function isExhaustEndedUnexpectedly(e: unknown): boolean {
  return e?.constructor?.name === 'MongoUnexpectedServerResponseError' && /moreToCome/.test((e as any)?.message ?? '');
}

let resumeToken;
while (true) {
  const cs = coll.watch([], { resumeAfter: resumeToken });
  try {
    for await (const change of cs) { resumeToken = change._id; handle(change); }
  } catch (e) {
    if (isExhaustEndedUnexpectedly(e)) continue; // reconnect and resume
    throw e;
  }
}

When it happens

Trigger: Using exhaustCommand (change streams, certain legacy exhaust getMore paths) where the server stops sending moreToCome frames without the driver initiating cursor close. Happens when the server kills the cursor, the connection is reset mid-stream, or a proxy buffers/terminates the long-lived stream.

Common situations: Change streams behind a buffering proxy (nginx, envoy) with response buffering on; server-side cursor timeout or killCursors; network interruption during a long-running change stream; load balancers that do not support HTTP/1.1-style streaming for raw TCP.

Related errors

• ChangeStream is closed
• Unable to get response from server
• Unknown compressor failed to compress

AI-assisted analysis of mongodb/node-mongodb-native@dce7939f86 (2026-08-11). Data as JSON: /api/errors/3a7afb3e88866265. Report an issue: GitHub.

Appendix: source

Thrown at src/cmap/connection.ts:676

      return document;
    }
    throw new MongoUnexpectedServerResponseError('Unable to get response from server');
  }

  public exhaustCommand(
    ns: MongoDBNamespace,
    command: Document,
    options: CommandOptions,
    replyListener: Callback
  ) {
    const exhaustLoop = async () => {
      this.throwIfAborted();
      for await (const reply of this.sendCommand(ns, command, options)) {
        replyListener(undefined, reply);
        this.throwIfAborted();
      }
      throw new MongoUnexpectedServerResponseError('Server ended moreToCome unexpectedly');
    };

    exhaustLoop().then(undefined, replyListener);
  }

  private throwIfAborted() {
    if (this.error) throw this.error;
  }

  /**
   * @internal
   *
   * Writes an OP_MSG or OP_QUERY request to the socket, optionally compressing the command. This method
   * waits until the socket's buffer has emptied (the Nodejs socket `drain` event has fired).
   */
  private async writeCommand(
    command: WriteProtocolMessageType,
    options: {

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