Task logs - produced by AsyncPeriodicWork / AsyncAperiodicWork under $JENKINS_HOME/log/tasks) - can grow very big. We have seen instance with files that account for up to 10s of GBs.

In most cases the culprit is https://github.com/jenkinsci/jenkins/blob/master/core/src/main/java/hudson/model/WorkspaceCleanupThread.java and most recently https://github.com/jenkinsci/jenkins/blob/master/core/src/main/java/jenkins/model/BackgroundGlobalBuildDiscarder.java.

Although the fact that a file grows in size is usually indicative of an issue that needs to be addressed with that particular task, we think that Jenkins should be defensive and have a size limit. Large instance are also likely to see large task logs especially from tasks that operate on each item and log a record for each of them.

By default, those logs are rotated once a day, but not limited in size. Gigabyte of data can bring you close to your storage limit and cause much more critical problems that just consuming disk space.

Jenkins core should:

• adjust those defaults
• warn users when a specific task is reaching the size limit