[OAK-2143] NodeObservor should catch exception in case event processing

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.0.7, 1.1.1
• Component/s: core
• Assignee: Chetan Mehrotra
• Reporter: Chetan Mehrotra
• Created: 26/Sep/14 06:48
• Updated: 13/Oct/14 09:20
• Resolved: 01/Oct/14 06:42

Description

Currently NodeObservor does not catch any exception which might occur while event generation [1] while the ChangeDispatcher does catch the exception [2].

Due to this if any exception occurs while generating events in NodeObservor the previousState would not be reset. For next contentChanged call would trigger a diff from same old previousState and might again fail with same exception [3]. This would cause duplicate events to be generated. To keep things consistent NodeObservor should also catch and ignore exception (log it and move on) as it is done in ChangeDispatcher

[1] https://github.com/apache/jackrabbit-oak/blob/1.0/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/observation/NodeObserver.java#L120
[2] https://github.com/apache/jackrabbit-oak/blob/1.0/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/observation/ChangeProcessor.java#L268
[3] Exception seen here is caused due to some bug in DocumentNodeStore (being investigated separately)

24.09.2014 09:13:55.668 *ERROR* [pool-5-thread-5] org.apache.sling.jcr.resource.internal.OakResourceListener Uncaught exception in org.apache.sling.jcr.resource.internal.OakResourceListener@7c9c3fbb
java.lang.NullPointerException: Node at [/var/eventing/jobs/assigned/62f1f24b-027e-4434-b1ef-a7a3c2c90e16/logouttopic/2014/9/24/15/12] not found for fromRev [r148a837accc-0-4]
	at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:236)
	at org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.diffFewChildren(DocumentNodeStore.java:1628)
	at org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.diffImpl(DocumentNodeStore.java:1533)
	at org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.diffChildren(DocumentNodeStore.java:1210)
	at org.apache.jackrabbit.oak.plugins.document.DocumentNodeState.compareAgainstBaseState(DocumentNodeState.java:252)
	at org.apache.jackrabbit.oak.plugins.observation.EventGenerator$Continuation.run(EventGenerator.java:151)
	at org.apache.jackrabbit.oak.plugins.observation.EventGenerator.generate(EventGenerator.java:98)
	at org.apache.jackrabbit.oak.plugins.observation.NodeObserver.contentChanged(NodeObserver.java:155)
	at org.apache.jackrabbit.oak.spi.commit.BackgroundObserver$1$1.call(BackgroundObserver.java:117)
	at org.apache.jackrabbit.oak.spi.commit.BackgroundObserver$1$1.call(BackgroundObserver.java:111)
	at java.util.concurrent.FutureTask.run(FutureTask.java:262)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:744)

Issue Links

• relates to: OAK-2144 Intermittent Node not found at given revision with DocumentNodeStore