[CAMEL-16025] [camel-mongodb] ChangeStreams: Exception not gracefully handled

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.7.0
• Fix Version/s: 3.10.0
• Component/s: camel-mongodb
• Estimated Complexity: Unknown
• Assignee: Claus Ibsen
• Reporter: Dario Nuevo
• Created: 12/Jan/21 13:37
• Updated: 22/Mar/21 17:26
• Resolved: 22/Mar/21 17:26

Description

I'm a bit confused how it should be handled when an Exception happens during the watch() in MongoDbChangeStreamsThread.

I observed that the Mongo Client throws an Exception if the collection the watch() is on is deleted (the whole collection) - it that case, this exception is thrown:

Exception in thread "Camel (camel-1) thread #1 - mongodb://mongoConnection" java.lang.NullPointerException
	at org.apache.camel.component.mongodb.MongoDbChangeStreamsThread.doRun(MongoDbChangeStreamsThread.java:74)
	at org.apache.camel.component.mongodb.MongoAbstractConsumerThread.run(MongoAbstractConsumerThread.java:68)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:830)

After the exception, Camel keeps running, the route is still "started", but no Changestreams _watch()_es are active - so we are in a strange state.

Exceptions can happen quite often using changeStreams - I think it should be documented how the user should handle this. Or if this is an error and the changestream watch() should be restarted, that should be fixed.