[JENKINS-66446] WebSocket agent does not reconnect: ClassNotFoundException: jenkins.slaves.restarter.JnlpSlaveRestarterInstaller

I'm using jenkins helm <a href="https://github.com/jenkinsci/helm-charts/tree/main/charts/jenkins" class="external-link" target="_blank" rel="nofollow noopener">chart</a> for my jenkins controller (master) with persistence EFS volume together with Kubernetes plugin with inbound-agent (jdk11) pods for my agents (slaves) over websocket connection

It seems that the Agent (slave) pods are unable to re-connect the controller (master) after a reboot to the controller (master).

It seems that the process exit with exit code 0 from some reason instead of reconnecting.

 

jenkins controller (master) log

<pre>
2021-08-24 13:26:33.976+0000 [id=64] INFO o.c.j.p.k.KubernetesLauncher#launch: Agent has already been launched, activating: jenkins-agent-3q3j5
</pre>
 

jenkins agent (slave) log:

<pre>
Aug 24, 2021 1:23:56 PM hudson.remoting.Engine lambda$new$1
Aug 24, 2021 1:23:56 PM hudson.remoting.Engine lambda$new$1SEVERE: Uncaught exception in Engine thread Thread[Thread-0,5,main]
java.lang.NoClassDefFoundError: jenkins/slaves/restarter/JnlpSlaveRestarterInstaller 
 at jenkins.slaves.restarter.JnlpSlaveRestarterInstaller$FindEffectiveRestarters$1.onReconnect(JnlpSlaveRestarterInstaller.java:91) 
 at hudson.remoting.EngineListenerSplitter.onReconnect(EngineListenerSplitter.java:54) 
 at hudson.remoting.Engine.runWebSocket(Engine.java:687) 
 at hudson.remoting.Engine.run(Engine.java:496)
Caused by: java.lang.ClassNotFoundException: jenkins.slaves.restarter.JnlpSlaveRestarterInstaller 
 at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471) 
 at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:215) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:589) 
 at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522) ... 4 more
</pre>
 

jenkins agent (slave) pod status:

<pre>
NAME READY STATUS RESTARTS AGE
jenkins-agent-3q3j5 1/2 NotReady 0 15m


 lastState: {}
 name: jnlp
 ready: false
 restartCount: 0
 started: false
 state:
 terminated:
containerID: docker://9b490eafd5078fa95cbd915bed16bcee767c1005a7a96158a2017d1551fba87b
exitCode: 0
finishedAt: "2021-09-08T15:00:07Z"
reason: Completed
startedAt: "2021-09-08T14:53:19Z"

</pre>
 

 inbound-agent conf

<pre>
 - name: JENKINS_SECRET
 value: 271983729187392173921798379281739821793b
 - name: JENKINS_AGENT_NAME
 value: jenkins-agent-3q3j5
 - name: DOCKER_HOST
 value: tcp://localhost:2375
 - name: JENKINS_WEB_SOCKET
 value: "true"
 - name: JAVA_OPTS
 value: -Xms512m -Xmx1500m
 - name: JENKINS_NAME
 value: jenkins-agent-3q3j5
 - name: JENKINS_AGENT_WORKDIR
 value: /home/jenkins/agent
 - name: JENKINS_URL
 value: http://jenkins:8080/
 - name: AWS_DEFAULT_REGION
 value: us-east-1
 - name: AWS_REGION
 value: us-east-1
 - name: AWS_ROLE_ARN
 value: arn:aws:iam::123456789:role/jenkins-agent-pod
 - name: AWS_WEB_IDENTITY_TOKEN_FILE
 value: /var/run/secrets/eks.amazonaws.com/serviceaccount/token
</pre>
 

jenkins agent (slave) pod process

<pre>
/opt/java/openjdk/bin/java -Xms512m -Xmx1500m -cp /usr/share/jenkins/agent.jar hudson.remoting.jnlp.Main -headless -url http://jenkins:8080/ -workDir /home /jenkins/agent -webSocket 271983729187392173921798379281739821793b jenkins-agent-3q3j5
</pre>
 

same behavior in

<pre>
jenkins/jenkins:2.303.1-jdk11
jenkins/inbound-agent:4.10-2-jdk11
</pre>
 

It seems that this issue happens also on windows agent (slave)

 

might be related: <a href="https://issues.jenkins.io/browse/JENKINS-59910" class="external-link" rel="nofollow">https://issues.jenkins.io/browse/JENKINS-59910</a>

---
<details><summary>Originally reported by <a href="https://issues.jenkins.io/secure/ViewProfile.jspa?name=dordor">dordor</a>, imported from: <a class="no-jira-link-rewrite" href="https://issues.jenkins.io/browse/JENKINS-66446" target="_blank">WebSocket agent does not reconnect: ClassNotFoundException: jenkins.slaves.restarter.JnlpSlaveRestarterInstaller</a></summary>
<ul>
<li>assignee: <img align="left" width="20" src="https://raw.githubusercontent.com/jenkinsci/artifacts-from-jira-issues/refs/heads/main/avatars/timja.png" title="timja's avatar" /> <a href="https://issues.jenkins.io/secure/ViewProfile.jspa?name=timja">timja</a>
<li>status: Closed
<li>priority: Critical
<li>component(s): remoting
<li>label(s): 2.332.2-fixed, java11
<li>resolution: Fixed
<li>resolved: 2022-03-04T03:46:30+00:00
<li>votes: 1
<li>watchers: 6
<li>imported: 2025-11-25
</ul>
<details><summary>Raw content of original issue</summary>

<pre>
I'm using jenkins helm <a href="https://github.com/jenkinsci/helm-charts/tree/main/charts/jenkins" class="external-link" target="_blank" rel="nofollow noopener">chart</a> for my jenkins controller (master) with persistence EFS volume together with Kubernetes plugin with inbound-agent (jdk11) pods for my agents (slaves) over websocket connection

It seems that the Agent (slave) pods are unable to re-connect the controller (master) after a reboot to the controller (master).

It seems that the process exit with exit code 0 from some reason instead of reconnecting.

 

jenkins controller (master) log
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">2021-08-24 13:26:33.976+0000 [id=64] INFO o.c.j.p.k.KubernetesLauncher#launch: Agent has already been launched, activating: jenkins-agent-3q3j5
</pre>
</div></div>
 

jenkins agent (slave) log:
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">Aug 24, 2021 1:23:56 PM hudson.remoting.Engine lambda$new$1
Aug 24, 2021 1:23:56 PM hudson.remoting.Engine lambda$new$1SEVERE: Uncaught exception in Engine thread Thread[Thread-0,5,main]
java.lang.NoClassDefFoundError: jenkins/slaves/restarter/JnlpSlaveRestarterInstaller 
 at jenkins.slaves.restarter.JnlpSlaveRestarterInstaller$FindEffectiveRestarters$1.onReconnect(JnlpSlaveRestarterInstaller.java:91) 
 at hudson.remoting.EngineListenerSplitter.onReconnect(EngineListenerSplitter.java:54) 
 at hudson.remoting.Engine.runWebSocket(Engine.java:687) 
 at hudson.remoting.Engine.run(Engine.java:496)
Caused by: java.lang.ClassNotFoundException: jenkins.slaves.restarter.JnlpSlaveRestarterInstaller 
 at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471) 
 at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:215) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:589) 
 at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522) ... 4 more
</pre>
</div></div>
 

jenkins agent (slave) pod status:
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">NAME READY STATUS RESTARTS AGE
jenkins-agent-3q3j5 1/2 NotReady 0 15m


 lastState: {}
 name: jnlp
 ready: false
 restartCount: 0
 started: false
 state:
 terminated:
 containerID: docker://9b490eafd5078fa95cbd915bed16bcee767c1005a7a96158a2017d1551fba87b
 exitCode: 0
 finishedAt: "2021-09-08T15:00:07Z"
 reason: Completed
 startedAt: "2021-09-08T14:53:19Z"

</pre>
</div></div>
 

 inbound-agent conf
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java"> - name: JENKINS_SECRET
 value: 271983729187392173921798379281739821793b
 - name: JENKINS_AGENT_NAME
 value: jenkins-agent-3q3j5
 - name: DOCKER_HOST
 value: tcp://localhost:2375
 - name: JENKINS_WEB_SOCKET
 value: "true"
 - name: JAVA_OPTS
 value: -Xms512m -Xmx1500m
 - name: JENKINS_NAME
 value: jenkins-agent-3q3j5
 - name: JENKINS_AGENT_WORKDIR
 value: /home/jenkins/agent
 - name: JENKINS_URL
 value: http://jenkins:8080/
 - name: AWS_DEFAULT_REGION
 value: us-east-1
 - name: AWS_REGION
 value: us-east-1
 - name: AWS_ROLE_ARN
 value: arn:aws:iam::123456789:role/jenkins-agent-pod
 - name: AWS_WEB_IDENTITY_TOKEN_FILE
 value: /var/run/secrets/eks.amazonaws.com/serviceaccount/token
</pre>
</div></div>
 

jenkins agent (slave) pod process
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">/opt/java/openjdk/bin/java -Xms512m -Xmx1500m -cp /usr/share/jenkins/agent.jar hudson.remoting.jnlp.Main -headless -url http://jenkins:8080/ -workDir /home /jenkins/agent -webSocket 271983729187392173921798379281739821793b jenkins-agent-3q3j5
</pre>
</div></div>
 

same behavior in
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">jenkins/jenkins:2.303.1-jdk11
jenkins/inbound-agent:4.10-2-jdk11
</pre>
</div></div>
 

It seems that this issue happens also on windows agent (slave)

 

might be related: <a href="https://issues.jenkins.io/browse/JENKINS-59910" class="external-link" rel="nofollow">https://issues.jenkins.io/browse/JENKINS-59910</a></pre>
</details>
</details>
<details><summary>environment</summary>

```
Jenkins: 2.303.1 
jenkins k8s controller (master) pod version: jenkins/jenkins:2.289.3-jdk11 
jenkins k8s agent (slave) pod version:&#xA0; jenkins/inbound-agent:4.9-1-jdk11 
Kubernetes plugin: 1.30.1
```
</details>

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[JENKINS-66446] WebSocket agent does not reconnect: ClassNotFoundException: jenkins.slaves.restarter.JnlpSlaveRestarterInstaller #1448

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[JENKINS-66446] WebSocket agent does not reconnect: ClassNotFoundException: jenkins.slaves.restarter.JnlpSlaveRestarterInstaller #1448

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