[FLINK-5142] Resource leak in CheckpointCoordinator

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.1.1, 1.1.2, 1.1.3
• Fix Version/s: 1.1.4
• Component/s: Runtime / State Backends
• Assignee: Stephan Ewen
• Reporter: Frank Lauterwald
• Created: 23/Nov/16 09:33
• Updated: 28/Nov/16 17:32
• Resolved: 28/Nov/16 17:32

Description

We run Flink 1.1.3 with a fairly aggressive time between checkpoints and a minimum interval between checkpoints to make sure that some work gets done between checkpoints.
Over time, the JobManager uses more and more CPU time until it saturates the available cores. It does not show heavy I/O load and the task managers seem to work without problems.
We see lots of log messages of the form "Trying to trigger another checkpoint while one was queued already" - sometimes multiple in the same millisecond.
It seems like checkpoints are triggered way too often.

I suspect there is a resource leak in the CheckpointCoordinator which leads to this behavior:

// in triggerCheckpoint(long timestamp, long nextCheckpointId), line 414ff
// introduced as part of FLINK-3492
if (lastTriggeredCheckpoint + minPauseBetweenCheckpoints > timestamp) {
if (currentPeriodicTrigger != null)

{ currentPeriodicTrigger.cancel(); currentPeriodicTrigger = null; }

ScheduledTrigger trigger = new ScheduledTrigger();
timer.scheduleAtFixedRate(trigger, minPauseBetweenCheckpoints, baseInterval);
return false;
}

The newly created trigger is not assigned to currentPeriodicTrigger, so it cannot be cancelled whenever another rescheduling is required.
If rescheduling is common (it happens several times per minute for us), the running triggers accumulate until they overwhelm the JobManager.

Versions up to Flink 1.0.x are unaffected because FLINK-3492 is a Flink 1.1 feature.
The issue seems to be already fixed in master by commit 8854d75c due to (unrelated) work on FLINK-4322.

Let me know if there's anything else I can do to help.