[jira] [Resolved] (AMQ-5198) MessageConsumer and Producer are not thread safe

["Timothy Bish (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AMQ-5198?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Timothy Bish resolved AMQ-5198.
-------------------------------

       Resolution: Fixed
    Fix Version/s: 5.11.0

Fixed the assignment of the member variable to occur after the created scheduler is initialized so that the initialization doesn't allow the instance to escape the synchronized block.  

> MessageConsumer and Producer are not thread safe
> ------------------------------------------------
>
>                 Key: AMQ-5198
>                 URL: https://issues.apache.org/jira/browse/AMQ-5198
>             Project: ActiveMQ
>          Issue Type: Bug
>    Affects Versions: 5.9.0
>            Reporter: Enrico Musuruana
>             Fix For: 5.11.0
>
>         Attachments: ActiveMq.zip
>
>
> We currently have an object that acts both as a consumer and as a producer over the same queue.
> Lazy initialization of the scheduler is not 100% thread safe when a consumer and a producer are created sharing the same connection.
> We encountered the following sporadic NPE when a rollback() is invoked:
> Caused by: java.lang.NullPointerException
>         at org.apache.activemq.thread.Scheduler.executeAfterDelay(Scheduler.java:64)
>         at org.apache.activemq.ActiveMQMessageConsumer.rollback(ActiveMQMessageConsumer.java:1278)
>         at org.apache.activemq.ActiveMQMessageConsumer$5.afterRollback(ActiveMQMessageConsumer.java:1054)
>         at org.apache.activemq.TransactionContext.afterRollback(TransactionContext.java:157)
>         ... 11 more
> We believe that the lazy initialized getScheduler() is open for a race condition when a publish and rollback are happening concurrently.
> try {
>                         result = scheduler = new Scheduler("ActiveMQConnection["+info.getConnectionId().getValue()+"] Scheduler");
>                         scheduler.start();
>                     } catch(Exception e) {
>                         throw JMSExceptionSupport.create(e);
>                     }
> The suggested fix is to simply invoke the start within the constructor of the Scheduler class.



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