WebSocket Jenkins agent disconnects (java.util.concurrent.TimeoutException: Ping started at 1775776035301 hasn't completed by 1775776275302)

Using Jenkins Ask a question
1

Hi,

We are seeing random disconnects on our Jenkins inbound agents using WebSocket.

Jenkins version: 2.541.3
Remoting version: 3352.v17a_fb_4b_2773f
Agent Java: OpenJDK 21.0.10
Controller Java: OpenJDK 21.0.9 Temurin

Our setup is:

agent → AWS Global Accelerator → ALB → Jenkins controller

What we are seeing:

  • Agents disconnect randomly, sometimes even while a job is running

  • On the agent side we see:

    Ping failed. Terminating the channel
java.util.concurrent.TimeoutException: Ping started at ... hasn't completed by ...
    at hudson.remoting.PingThread.ping
    at hudson.remoting.PingThread.run

INFO: Write side closed
INFO: Read side closed
INFO: Terminated
INFO: Performing onReconnect operation

  • Immediately after that, the agent reconnects and comes back online

  • On the controller side we mostly only see:

    INFO	j.s.DefaultJnlpSlaveReceiver#channelClosed: Jetty (winstone)-194376 for .... terminated: java.nio.channels.ClosedChannelException

What we checked so far:

  • Agent machine looks healthy

  • ALB logs do not show clear errors like 460/504 around the disconnect window

  • Connection is over WebSocket on HTTPS (443)

So it does not look like a normal node crash. It feels like the connection stops responding for some time and Jenkins later closes it due to ping timeout.

Questions:

  1. Has anyone seen WebSocket agents disconnect like this without clear errors?

  2. Could this be related to Jenkins remoting or WebSocket handling?

  3. Are there recommended settings for ping interval / timeout or WebSocket keepalive?

Thanks!

2

We’re seeing the same problem in Jenkins with the same version, and it’s making builds unstable. Any suggestions would be appreciated.

3

We tried AWS GA as well, but nothing worked and we experienced different types of errors. Since the issue is still related to disconnection, we are moving to use an AWS ALB for the Jenkins URL and an AWS NLB for the node connection.

REF: Inbound WebSocket Jenkins agent intermittently disconnects with Connection timed out / Read side closed · Issue #26726 · jenkinsci/jenkins · GitHub

4

will reply you back in week, about stability using NLB

5

We observed improved stability after moving the node connections to the AWS NLB.