[KAFKA-6277] Make loadClass thread-safe for class loaders of Connect plugins

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.11.0.2, 1.0.0
• Fix Version/s: 0.11.0.3, 1.0.1, 1.1.0
• Component/s: connect
• Assignee: Konstantine Karantasis
• Reporter: Konstantine Karantasis
• Created: 28/Nov/17 03:19
• Updated: 22/Jan/18 03:42
• Resolved: 22/Jan/18 03:42

Description

In Connect's classloading isolation framework, PluginClassLoader class encounters a race condition when several threads corresponding to tasks using a specific plugin (e.g. a Connector) try to load the same class at the same time on a single JVM.

The race condition is related to calls to method defineClass which, contract to findClass, is not thread safe for classloaders that override loadClass. More details here:

https://docs.oracle.com/javase/7/docs/technotes/guides/lang/cl-mt.html

Issue Links

• links to: GitHub Pull Request #4428