Agent Connectivity Issue After Jenkins Upgrade to 2.555.1

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1

After upgrading Jenkins from version 2.528.3 to 2.555.1, we are experiencing agent connectivity issues with the Jenkins controller. The error message displayed is: “This node is offline because it uses an old agent.jar.”

We attempted to resolve this by downloading the latest swarm.jar and also tested with different versions of the Swarm client JAR, but the issue persists. Both the Jenkins controller and agents have been upgraded to Java 21.

Please suggest a resolution.

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2

You need to download and execute the latest swarm-client.jar. The plugin documentation says:

  1. Install the Swarm plugin from the Update Center.
  2. Ensure your agent is running version 11 or later of the Java Runtime Environment (JRE). The recommendation is to use the same JRE distribution and version as the controller.
  3. Download the Swarm client from ${JENKINS_URL}/swarm/swarm-client.jar on your agent.
  4. Run the Swarm client with java -jar path/to/swarm-client.jar -url ${JENKINS_URL} -username ${USERNAME} and one of the authentication options as described in the Global Security Configuration documentation. There are no other required command-line options; run with the -help option to see the available options.

When I follow those steps, the swarm agent that connects to my controller is using the same version of remoting as is provided with Jenkins 2.555.1.

If you’d like to monitor the version of remoting used by your agents, you can use the Versions Node Monitors plugin: