Underlying issue
Reactor run method (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L115) only catches TunnelException.
If another exception occurs in the task run method,
- done is set to true
- fatal is not set
- but pending variable is not decremented
This makes Reactor execute method wait for ever (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L266) as pending will never reach 0.
How can task.run throw something else than a TunnelException?
task run method (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L207) catches exceptions from the runTask method and wraps them in a TunnelException.
But listener methods are not protected by try/catch blocks (except onTaskCompleted for technical reasons)
So if an exception occurs in any of the onTaskStarted or onTaskFailed, it won't be wrapped in a TunnelException, making the problem arise.
For milestones, another type of run method is used (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L176), calling the listener's onAttained method, unprotected by try/catch.
Even if it can make sense not to protect listener methods, I am wondering if this is a good idea to have different behaviors depending on the listener method as one of them is in fact protected?
Where does a listener throw an exception?
InitReactorRunner provides a listener implementation calling InitReactorRunner's onInitMilestoneAttained method, when onAttained is called on a milestone of type InitMilestone.
|
onInitMilestoneAttained((InitMilestone) milestone); |
onInitMilestoneAttained implementation in Jenkins class (https://github.com/jenkinsci/jenkins/blob/a82a47a8f2a90727d873c637c99aa0d087500dfe/core/src/main/java/jenkins/model/Jenkins.java#L1092) can throw if ExtensionList.lookup(ExtensionFinder.class).getComponents(); throws.
Exceptions can occur through a static call to a plugin class in an exception point if this same plugin will not start for a dependency reason
Note that even if this seems an advanced scenario, other implementations of _ReactorListener_s could be provided through https://github.com/jenkinsci/jenkins/blob/a82a47a8f2a90727d873c637c99aa0d087500dfe/core/src/main/java/jenkins/InitReactorRunner.java#L63, and they might provide implementations which throw exception.
How to correct?
I would have proposed a fix, but I'm not sure of the direction to take:
- enhance the Reactor component
- by protecting listeners calls ?
- by adding a way for listener methods to mark the task as fatal for milestones?
- work around the limitations on listeners error-handling in Jenkins core code
- by try catching, logging, and swallowing the exception (not sure of the consequences) ?
- or by adding back to the reactor a task designed to throw the exception in case of errors (will occur at some unknown point in the future, but at least will stop Jenkins startup) ?
- just fix all plugins ?
- some other way?
Originally reported by 
greybird, imported from: Jenkins startup workflow can deadlock if exceptions occur during extensions lookup
- assignee: greybird
- status: Resolved
- priority: Major
- component(s): core
- label(s): exception, lib-task-reactor, robustness
- resolution: Fixed
- resolved: 2018-02-17T09:41:19+00:00
- votes: 0
- watchers: 4
- imported: 2025-11-24
Raw content of original issue
Underlying issue
Reactor run method (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L115) only catches TunnelException.
If another exception occurs in the task run method,
- done is set to true
- fatal is not set
- but pending variable is not decremented
This makes Reactor execute method wait for ever (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L266) as pending will never reach 0.
How can task.run throw something else than a TunnelException?
task run method (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L207) catches exceptions from the runTask method and wraps them in a TunnelException.
But listener methods are not protected by try/catch blocks (except onTaskCompleted for technical reasons)
So if an exception occurs in any of the onTaskStarted or onTaskFailed, it won't be wrapped in a TunnelException, making the problem arise.
For milestones, another type of run method is used (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L176), calling the listener's onAttained method, unprotected by try/catch.
Even if it can make sense not to protect listener methods, I am wondering if this is a good idea to have different behaviors depending on the listener method as one of them is in fact protected?
Where does a listener throw an exception?
InitReactorRunner provides a listener implementation calling InitReactorRunner's onInitMilestoneAttained method, when onAttained is called on a milestone of type InitMilestone.
|
onInitMilestoneAttained((InitMilestone) milestone); |
onInitMilestoneAttained implementation in Jenkins class (https://github.com/jenkinsci/jenkins/blob/a82a47a8f2a90727d873c637c99aa0d087500dfe/core/src/main/java/jenkins/model/Jenkins.java#L1092) can throw if ExtensionList.lookup(ExtensionFinder.class).getComponents(); throws.
Exceptions can occur through a static call to a plugin class in an exception point if this same plugin will not start for a dependency reason
Note that even if this seems an advanced scenario, other implementations of _ReactorListener_s could be provided through https://github.com/jenkinsci/jenkins/blob/a82a47a8f2a90727d873c637c99aa0d087500dfe/core/src/main/java/jenkins/InitReactorRunner.java#L63, and they might provide implementations which throw exception.
How to correct?
I would have proposed a fix, but I'm not sure of the direction to take:
- enhance the Reactor component
- by protecting listeners calls ?
- by adding a way for listener methods to mark the task as fatal for milestones?
- work around the limitations on listeners error-handling in Jenkins core code
- by try catching, logging, and swallowing the exception (not sure of the consequences) ?
- or by adding back to the reactor a task designed to throw the exception in case of errors (will occur at some unknown point in the future, but at least will stop Jenkins startup) ?
- just fix all plugins ?
- some other way?
- environment:
Jenkins v2.89.2
Underlying issue
Reactor run method (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L115) only catches TunnelException.
If another exception occurs in the task run method,
This makes Reactor execute method wait for ever (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L266) as pending will never reach 0.
How can task.run throw something else than a TunnelException?
task run method (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L207) catches exceptions from the runTask method and wraps them in a TunnelException.
But listener methods are not protected by try/catch blocks (except onTaskCompleted for technical reasons)
So if an exception occurs in any of the onTaskStarted or onTaskFailed, it won't be wrapped in a TunnelException, making the problem arise.
For milestones, another type of run method is used (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L176), calling the listener's onAttained method, unprotected by try/catch.
Where does a listener throw an exception?
InitReactorRunner provides a listener implementation calling InitReactorRunner's onInitMilestoneAttained method, when onAttained is called on a milestone of type InitMilestone.
jenkins/core/src/main/java/jenkins/InitReactorRunner.java
Line 83 in a82a47a
onInitMilestoneAttained implementation in Jenkins class (https://github.com/jenkinsci/jenkins/blob/a82a47a8f2a90727d873c637c99aa0d087500dfe/core/src/main/java/jenkins/model/Jenkins.java#L1092) can throw if ExtensionList.lookup(ExtensionFinder.class).getComponents(); throws.
Exceptions can occur through a static call to a plugin class in an exception point if this same plugin will not start for a dependency reason
How to correct?
I would have proposed a fix, but I'm not sure of the direction to take:
Originally reported by
greybird, imported from: Jenkins startup workflow can deadlock if exceptions occur during extensions lookup
Raw content of original issue
This makes Reactor execute method wait for ever (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L266) as pending will never reach 0.
How can task.run throw something else than a TunnelException?
task run method (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L207) catches exceptions from the runTask method and wraps them in a TunnelException.
But listener methods are not protected by try/catch blocks (except onTaskCompleted for technical reasons)
So if an exception occurs in any of the onTaskStarted or onTaskFailed, it won't be wrapped in a TunnelException, making the problem arise.
For milestones, another type of run method is used (https://github.com/jenkinsci/lib-task-reactor/blob/master/src/main/java/org/jvnet/hudson/reactor/Reactor.java#L176), calling the listener's onAttained method, unprotected by try/catch.
Where does a listener throw an exception?
InitReactorRunner provides a listener implementation calling InitReactorRunner's onInitMilestoneAttained method, when onAttained is called on a milestone of type InitMilestone.
jenkins/core/src/main/java/jenkins/InitReactorRunner.java
Line 83 in a82a47a
onInitMilestoneAttained implementation in Jenkins class (https://github.com/jenkinsci/jenkins/blob/a82a47a8f2a90727d873c637c99aa0d087500dfe/core/src/main/java/jenkins/model/Jenkins.java#L1092) can throw if ExtensionList.lookup(ExtensionFinder.class).getComponents(); throws.
Exceptions can occur through a static call to a plugin class in an exception point if this same plugin will not start for a dependency reason
How to correct?
I would have proposed a fix, but I'm not sure of the direction to take:
Jenkins v2.89.2