[CAMEL-4447] thread safety issue with Exchange.getUnitOfWork()

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.8.1
• Fix Version/s: 2.8.2, 2.9.0
• Component/s: camel-core

Environment

JDK 1.6.0_20 on Linux x86_64

• Estimated Complexity: Unknown
• Assignee: Claus Ibsen
• Reporter: David Tombs
• Created: 13/Sep/11 20:30
• Updated: 12/Dec/11 17:31
• Resolved: 05/Oct/11 07:13

Description

I'm having a somewhat rare issue with NullPointerExceptions in a multithreaded route. It seems that there is a race condition between one thread operating on the UnitOfWork and another removing it. I have gotten the following stacktraces so far:

ERROR [Camel0 - Resequencer Delivery] o.a.c.p.StreamResequencer - Caused by: [java.lang.NullPointerException - null]
java.lang.NullPointerException: null
	at org.apache.camel.processor.DefaultChannel$1.done(DefaultChannel.java:309) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.RedeliveryErrorHandler.processErrorHandler(RedeliveryErrorHandler.java:349) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.RedeliveryErrorHandler.process(RedeliveryErrorHandler.java:209) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.DefaultChannel.process(DefaultChannel.java:305) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.util.AsyncProcessorHelper.process(AsyncProcessorHelper.java:78) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.Pipeline.process(Pipeline.java:116) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.Pipeline.process(Pipeline.java:79) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.util.AsyncProcessorHelper.process(AsyncProcessorHelper.java:104) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.Pipeline.process(Pipeline.java:59) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.StreamResequencer.sendElement(StreamResequencer.java:165) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.StreamResequencer.sendElement(StreamResequencer.java:61) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.resequencer.ResequencerEngine.deliverNext(ResequencerEngine.java:254) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.resequencer.ResequencerEngine.deliver(ResequencerEngine.java:218) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.StreamResequencer$Delivery.run(StreamResequencer.java:212) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]

And:

ERROR [Camel0 - Resequencer Delivery] o.a.c.p.StreamResequencer - Caused by: [java.lang.NullPointerException - null]
java.lang.NullPointerException: null
	at org.apache.camel.impl.DefaultExchange.isTransacted(DefaultExchange.java:331) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.util.AsyncProcessorHelper.process(AsyncProcessorHelper.java:57) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.Pipeline.process(Pipeline.java:116) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.Pipeline.process(Pipeline.java:79) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.util.AsyncProcessorHelper.process(AsyncProcessorHelper.java:104) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.Pipeline.process(Pipeline.java:59) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.StreamResequencer.sendElement(StreamResequencer.java:165) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.StreamResequencer.sendElement(StreamResequencer.java:61) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.resequencer.ResequencerEngine.deliverNext(ResequencerEngine.java:254) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.resequencer.ResequencerEngine.deliver(ResequencerEngine.java:218) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]
	at org.apache.camel.processor.StreamResequencer$Delivery.run(StreamResequencer.java:212) ~[camel-core-2.8.1-SNAPSHOT.jar:2.8.1-SNAPSHOT]

Looking at the source, both NullPointerExceptions were thrown by code like:

return getUnitOfWork() != null && getUnitOfWork().isTransacted();

Oddly, I've only seen this happen soon after startup and only once per run.

The actual route is company confidential, but it's basically:

JMS -> Stream Resequencer -> Bean