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https://issues.apache.org/jira/browse/CAMEL-14327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17004179#comment-17004179
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Rafał Gała commented on CAMEL-14327:
------------------------------------

I changed *isSingleton()* method to return true, but as a result, all threads 
were executing the process method on the same *Jt400PgmProducer* instance, so 
they shared the same iSeries object (connection). This may lead to 
unpredictable results. I modified the code to obtain *AS400* instance within 
*process()* method and release it back to the connection pool upon finishing.

Please take a look at proposed patch. I checked and the code worked. The amount 
of connections that were open to iSeries system were equal to amount of 
consumers on seda endpoint.

 

[^jt400.patch]

> Jt400PgmProducer doStop() method called on actively used instance
> -----------------------------------------------------------------
>
>                 Key: CAMEL-14327
>                 URL: https://issues.apache.org/jira/browse/CAMEL-14327
>             Project: Camel
>          Issue Type: Bug
>          Components: camel-jt400
>    Affects Versions: 3.0.0
>            Reporter: Rafał Gała
>            Priority: Major
>             Fix For: 3.0.1, 3.1.0
>
>         Attachments: jt400.patch
>
>
> Today I migrated to 3.0.0 version and there seems to be an issue with Service 
> pooling for the Jt400PgmpProducer.
>  
> Here's what I have:
>  
> {code:java}
>     from(
>         "seda:someName?concurrentConsumers=2&size=10")
>             
> .to("jt400://{{as400.user}}:{{as400.password}}@{{as400.host}}/QSYS.LIB/PROGRAM.LIB/KFKEVR.SRVPGM?fieldsLength=200,2000,4,8,8,1000&outputFieldsIdx=0,1,2,3,4,5&connectionPool=#as400ConnectionPool&format=binary&procedureName=RECEIVEEVENT");
> {code}
> When concurrentConsumers attribute of seda endpoint is set to 1 everything 
> works fine, but when it is greater than 1 then it looks like the evict method 
> from MultiplePool class calls stop method on a Jt400PgmProducer instance that 
> is still being used (the process method on it is still getting called). This 
> results in nulling the iSeries object inside Jt400PgmProducer instance:
> {code:java}
>     @Override
>     protected void doStop() throws Exception {
>         if (iSeries != null) {
>             LOG.info("Releasing connection to {}", getISeriesEndpoint());
>             getISeriesEndpoint().releaseSystem(iSeries);
>             iSeries = null;
>         }
>     }
> {code}
> and when the process method gets called later on this instance, it fails with 
> NPE while constructing ServiceProgramCall:
> {code:java}
>     @Override
>     public void process(Exchange exchange) throws Exception {
> ...
>             pgmCall = new ServiceProgramCall(iSeries);
> ...            
> {code}
>  
> I believe this may be related to producer caching in ServicePool class, some 
> sort of key issue in the cache Map maybe?



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