Ack Range

Overview

A single streaming delivery often bundles several messages together, but "successfully processed" rarely applies to all of them uniformly — one handler might fail while its siblings succeed. Acknowledging one message at a time works, but costs a round-trip per message; acknowledging the whole batch blindly risks confirming work that didn't actually finish. Range acknowledgment splits the difference: settle exactly the messages you know succeeded, in one call.

handle.ackRange(sequences) takes an array of broker-assigned sequence numbers — read off each message in the onMessages() callback — and acknowledges all of them together in a single server round-trip, instead of calling an individual ack for each one. Any sequence you leave out of the array stays unsettled and is redelivered once the session's visibility window expires.

Gotchas: the sequences you pass to ackRange must be numbers your handler actually received in that delivery — passing an unknown or already-settled sequence is a wasted (or erroring) call, not a no-op you can rely on. Messages you never include in any ackRange call aren't implicitly skipped forever; they come back for redelivery once the timeout elapses. And handle.close() ends the streaming session — call it only after you've settled everything you intend to, since messages still in flight when the handle closes are left for the next consumer.

Prerequisites

• KubeMQ server running on localhost:50000
• Node.js SDK installed (npm install kubemq-js)

Code

import { KubeMQClient, createQueueMessage } from 'kubemq-js';

async function main() {
  const client = await KubeMQClient.create({
    address: 'localhost:50000',
    clientId: 'js-queues-stream-ack-range-client',
  });

  try {
    for (let i = 0; i < 3; i++) {
      await client.sendQueueMessage(
        createQueueMessage({ channel: 'js-queues-stream.ack-range', body: `msg-${i}` }),
      );
    }

    const handle = client.streamQueueMessages({
      channel: 'js-queues-stream.ack-range',
      maxMessages: 3,
    });
    handle.onMessages((msgs) => {
      const sequences = msgs.map((m) => m.sequence);
      console.log('Received sequences:', sequences);
      handle.ackRange(sequences);
      console.log('Acknowledged range:', sequences);
      handle.close();
    });
    handle.onError((err) => {
      console.error('Error:', err.message);
    });

    await new Promise((r) => setTimeout(r, 2000));
  } finally {
    await client.close();
  }
}

main().catch(console.error);

How It Works

• streamQueueMessages() opens a streaming downstream session; onMessages() fires once the batch of up to maxMessages is delivered.
• handle.ackRange(sequences) acknowledges all messages whose sequence numbers appear in the array in a single server round-trip, more efficient than per-message acks.
• The sequence numbers come from m.sequence on each received QueueStreamMessage — the server assigns these monotonically per queue.
• handle.close() is called inside the onMessages callback to end the session after all messages are acknowledged; the outer setTimeout provides a safety timeout in case the callback never fires.

Related

• Pattern overview
• Node.js SDK Reference
• Send & Receive
• Ack All