TEIKITEETINI-VAYSSE Loic created CAMEL-11223:
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Summary: camel-jpa doesn't handle exclusive locks for concurrent
consumers
Key: CAMEL-11223
URL: https://issues.apache.org/jira/browse/CAMEL-11223
Project: Camel
Issue Type: Improvement
Components: camel-jpa
Affects Versions: 2.18.3
Environment: Java JDK 1.8.0_121
Spring 4 (reproduced with Spring Boot
RedHat RHEL 7.1 x86_64
Oracle 11G
Reporter: TEIKITEETINI-VAYSSE Loic
Deploying 4 instances of the same app containing a camel-jpa consumer polling
on the same database, I noticed that several servers can consume the same
entities.
The polling is currently done as follow :
# Poll without lock on the `maxResult` first rows
# On each row :
## Apply a lock _select ... for update (NOWAIT)_
## Consume entity
## Release the lock (commit)
What can happen with several instances of the consuming on the same database is
:
# {color:green}Server 1 polls the 10 first rows{color}
# {color:red}Server 2 polls the same 10 first rows{color}
# {color:green}Server 1 locks row 1 for update and consume it{color}
# {color:red}Server 2 locks row 1 for update as the previous lock is already
released and consumes it{color}
One fix could be to add a _@IsConsumed_ annotation defining a method to check
whether or not the entity has already been consumed. This method would be
called at the beginning of the _batchProcess_. That is the work around we
applied on our project but directly in our route ie without modifying the
component.
This demand is related to my previous post on the user forum :
http://camel.465427.n5.nabble.com/JPA-consumer-component-is-not-handling-multiple-server-concurrent-polling-td5797937.html
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