Poll Mode

Overview

Poll mode is a pull-based way to consume queue messages: the consumer decides exactly when to ask for work and how much, instead of holding an open stream the broker pushes into. That control matters for batch jobs, cron-triggered workers, and any consumer that only runs intermittently and would rather ask "is there anything for me?" than keep a subscription alive.

A single call to receiveQueueMessages() sends a channel, maxMessages, and waitTimeoutSeconds; the broker holds the request open as a long poll and returns once enough messages are available or the timeout elapses, so the call never spins on an empty queue. There's no persistent streaming session to manage — just a plain request and a batch of messages back.

Gotchas: messages received but not acked stay locked (invisible to other consumers) until the visibility timeout expires — always ack or nack in production code, unlike this minimal example; the timeout bounds latency, not throughput, so a small maxMessages on a busy queue means many round trips; and reach for streamQueueMessages() instead when you need continuous delivery callbacks or fine-grained ack/nack control in one long-lived session.

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-poll-mode-client',
  });

  try {
    await client.sendQueueMessage(
      createQueueMessage({ channel: 'js-queues-stream.poll-mode', body: 'poll-me' }),
    );

    const messages = await client.receiveQueueMessages({
      channel: 'js-queues-stream.poll-mode',
      maxMessages: 1,
      waitTimeoutSeconds: 5,
    });

    for (const msg of messages) {
      console.log('Polled:', new TextDecoder().decode(msg.body));
    }
    console.log('Total polled:', messages.length);
  } finally {
    await client.close();
  }
}

main().catch(console.error);

How It Works

• receiveQueueMessages() is a one-shot blocking poll: it waits up to waitTimeoutSeconds for up to maxMessages: 1 to become available and then returns.
• This is the simplest consumption model — no streaming session, no persistent handle. Call it in a loop to implement continuous polling.
• Messages received but not acked are locked (invisible to other consumers) until the visibility timeout expires. This example omits the ack to keep the demo minimal; production code should always ack or nack.
• Compare with streamQueueMessages() when you need batch delivery callbacks or fine-grained ack/nack/requeue control within the same session.

Related

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