[FLINK-16245] Use a delegating classloader as the user code classloader to prevent class leaks.

• Type: Improvement
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 1.12.0
• Component/s: Runtime / Task
• Labels: pull-request-available usability
• Assignee: Arvid Heise
• Reporter: Stephan Ewen
• Created: 23/Feb/20 16:43
• Updated: 04/Mar/22 13:59
• Resolved: 16/Aug/20 21:28

Description

As reported in FLINK-11205, a reference to the user-code ClassLoader can be held by some libraries, causing class leaks.

One way to circumvent this class leak is if the ClassLoader that we set as the user-code ClassLoader is a delegating ClassLoader to the real class loader, and when closing the user code ClassLoader we null out the reference.

Issue Links

• blocks: FLINK-16225 Metaspace Out Of Memory should be handled as Fatal Error in TaskManager
• fixes: FLINK-24080 FileCache can leak user code classloader
• links to: GitHub Pull Request #11303
• links to: GitHub Pull Request #13027