Jenkins Builds Fail with "Connection Refused" Error in Remote Node Setup

A rare but critical problem in Jenkins occurs when builds fail with a Connection Refused error when trying to execute jobs on a remote node.

This issue typically arises when Jenkins is unable to connect to a slave or agent node, preventing jobs from being executed on that node.

The first thing to check is whether the remote node is running and accessible from the Jenkins master.

If the remote node is down or not reachable, Jenkins will not be able to connect, and you will see the Connection Refused error.

Verify that the remote node is online and that the appropriate network configurations allow communication between the Jenkins master and the slave node.

If the node is running but still refusing connections, check the node’s firewall settings to ensure that the necessary ports are open.

Jenkins typically uses port 22 (SSH) or 8080 for communication, but this can vary based on your setup.

If the firewall is blocking these ports, the Jenkins master will not be able to establish a connection to the slave node.

Additionally, check the configuration of the slave node in Jenkins.

Navigate to Manage Jenkins > Manage Nodes and verify that the node configuration is correct, including the correct host, port, and credentials.

If the node uses SSH for communication, ensure that the correct SSH key is configured and that the key is authorized on the slave node.

Sometimes, incorrect permissions on the slave node’s file system can prevent Jenkins from connecting.

Ensure that the Jenkins user has the necessary permissions to read and write to the directories used for the Jenkins workspace and job execution.

Another potential issue is related to the Jenkins agent process.

If the agent process on the remote node has crashed or is not running, Jenkins will be unable to connect to the node.

Check the agent logs on the slave node to see if there are any error messages indicating why the agent is not functioning properly.

If necessary, restart the Jenkins agent on the remote node and attempt the connection again.

Finally, review the Jenkins master logs for any further error messages or warnings that may provide more details about the failed connection attempt.

Sometimes, misconfigured or conflicting network settings can prevent Jenkins from connecting to remote nodes, and the logs may provide clues for troubleshooting.

If the issue persists, consider recreating the remote node configuration to rule out any misconfigurations.