[AMQ-4710] The first heart-beat after a connection becomes idle isn't sent as quickly as it should be

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 5.8.0
• Fix Version/s: 5.x
• Component/s: STOMP
• Assignee: Timothy A. Bish
• Reporter: Andy Wilkinson
• Created: 02/Sep/13 12:21
• Updated: 29/Apr/21 15:59

Description

After ActiveMQ sends a stomp frame, it may not send a heart-beat for up to almost 2x the negotiated interval.

The following test should illustrate the problem:

import org.junit.Test;

import static org.junit.Assert.*;

public class ActiveMqHeartbeatTests {

	@Test
	public void heartbeats() throws Exception {
		BrokerService broker = createAndStartBroker();
		Socket socket = null;
		try {
			socket = new Socket("localhost", 61613);
			byte[] connectFrame = "CONNECT\nheart-beat:0,10000\naccept-version:1.2\n\n\0".getBytes();
			socket.getOutputStream().write(connectFrame);
			byte[] buffer = new byte[4096];

			long lastReadTime = System.currentTimeMillis();

			while (true) {
				int read = socket.getInputStream().read(buffer);
				byte[] frame = Arrays.copyOf(buffer, read);
				long now = System.currentTimeMillis();
				long timeSinceLastRead = now - lastReadTime;
				lastReadTime = now;
				System.out.println(new String(frame));
				System.out.println("Time since last read: " + timeSinceLastRead + "ms");
				if (timeSinceLastRead > 15000) {
					fail("Data not received for " + timeSinceLastRead + "ms");
				}
			}
		} finally {
			if (socket != null) {
				socket.close();
			}
			broker.stop();
		}
	}

	private BrokerService createAndStartBroker() throws Exception {
		BrokerService broker = new BrokerService();
		broker.addConnector("stomp://localhost:61613");
		broker.setStartAsync(false);
		broker.setDeleteAllMessagesOnStartup(true);
		broker.start();

		return broker;
	}

}

For the initial read of the CONNECTED frame I see:

Time since last read: 49ms

However, it's then almost 20 seconds before a heart-beat's sent:

Time since last read: 19994ms

If I comment out the fail(…) line in the test, after the first heartbeat taking almost 20000ms to be sent, things settle down and a heartbeat's received every 10000ms.

It looks like the write checker wakes up every 10000ms. The first time it wakes up, it notices that the CONNECTED frame was sent and does nothing. It then sleeps for a further 10000ms before checking again. As the CONNECTED frame was sent very early in the first 10000ms window, this leads to it taking almost 20000ms for the first heart-beat to be sent. From this point, as no further data frames are sent, the write checker wakes up and sends a heart-beat every 10000ms.

In short, I don't think ActiveMQ is adhering to the requirement that "the sender MUST send new data over the network connection at least every <n> milliseconds".