[jira] [Commented] (CAMEL-11223) camel-jpa doesn't handle exclusive locks for concurrent consumers when setting consumeDelete to false

["TEIKITEETINI-VAYSSE Loic (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CAMEL-11223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15994928#comment-15994928 ] 

TEIKITEETINI-VAYSSE Loic commented on CAMEL-11223:
--------------------------------------------------

After further analysis, I figured out that the consumeDelete parameter when set to true :
* By default consumes the entity by deleting it
* If an @Consumed or @PreConsumed method is defined, applies it (Besides this point is not very clear in the documentation :( http://camel.apache.org/jpa.html)

In a external POC I managed to use multiple concurrent pollers using consumeDelete=true and @Consumed or @PreConsumed.

Reality is, sometimes you want to externalize your model from your app and and just use it as a dependency. In that case, it is currently impossible to scan the @Consumed method.

As a workaround it is possible to manually consume the entity setting consumeDelete to false and using a bean to update the entity. In that particular case, the exclusive lock fails.

See attached a reproduction of the issue.

> camel-jpa doesn't handle exclusive locks for concurrent consumers when setting consumeDelete to false
> -----------------------------------------------------------------------------------------------------
>
>                 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 1.5.3)
> RedHat RHEL 7.1 x86_64
> Oracle 11G
>            Reporter: TEIKITEETINI-VAYSSE Loic
>         Attachments: jira-camel-11223.zip
>
>
> 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)
> ## New Transaction
> ## Process exchange
> ## End Transaction
> 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}
> 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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