[JENKINS-73119] Catch the class not found exception

[MarkEWaite]

JENKINS-73119 Catch the class not found exception

If the folders plugin is not installed, jobs fail to start and report: "Exception evaluating if the gueue can run the task"

Once the class not found exception is caught, then the job runs as expected.

Users that need the fix before a release is available can download it from Artifactory and install it on their controller. If plugin installation manager tool is being used, then the syntax to use the pull request build is:

build-blocker-plugin:incrementals;org.jenkins-ci.plugins;166.v7992612cb_4b_5

Testing done

Confirmed the failure by running Jenkins 2.426.3 with the build blocker plugin 165.v5ecb_fb_f61520 installed. I created a freestyle job and ran it. The run failed with the message "Exception evaluating if the gueue can run the task".

Confirmed the failure is resolved by installing the build of this commit and ran the same job without error. Confirmed that the class not found exception was written to the Jenkins logger when I enabled FINE logging for the BuildBlockerQueueTaskDispatcher. FINE logging is disabled by default, so the Jenkins log will not be cluttered by those exception messages unless an administrator specifically enables it.

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[jonesbusy]

@Denis1990 Hi, can you take a look at this ? I think its' worth to merge and let the CD do a release

I think the fine logger is fine. If the folder plugin is not installed, it just mean we cannot check if the property exists on parent folder. Therefore the job can run.

Perhaps the code could be improved to check if the plugin is installed instead of try/catch error

[Denis1990]

Thank you for the fix guys.
Will merge.

[jonesbusy]

Note: The main branch didn't build for some reason (flaky test ?). Also this PR must be labeled 'bug' for the CD to create a release

[MarkEWaite]

Note: The main branch didn't build for some reason (flaky test ?).

That looks like a flaky test. I've started the build on ci.jenkins.io again in hopes of confirming that.

Also this PR must be labeled 'bug' for the CD to create a release

Agreed.

[Denis1990]

I triggered a release manually, in order to publish the new release.