After upgrade gerrit trigger to 2.30, sometimes gerrit trigger can not trigger jenkins jobs, but the jenkins account can receive the gerrit stream events at the same time. We find a lot of WARNING logs in jenkins log, 

The Gerrit incoming events queue contains 6389 items! Something might be stuck, or your system can't process the commands fast enough. Try to increase the number of receiving worker threads. Current thead-pool size: 10.

By the way, we set gerrit-trigger only listening to change-merged and comment-added event types. Even we restart jenkins server, gerrit-trigger seems still stuck.