[jboss-jira] [JBoss JIRA] Commented: (JBAS-5904) ClientUserTransaction singleton initialisation is not thread safe

[Galder Zamarreno (JIRA)]

    [ https://jira.jboss.org/jira/browse/JBAS-5904?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12427544#action_12427544 ] 

Galder Zamarreno commented on JBAS-5904:
----------------------------------------

This issue affects transaction sticky functionality quite badly 
because the key of weak hashmap that maps transactions to
sticky nodes is a thread local within ClientUserTransaction. So, 
this bug lead to multiple ClientUserTransaction instances to be 
created and garbage collection previous ones, effectively 
removing transaction (tpc to be more precise) to sticky target 
mappings of on going transactions.

> ClientUserTransaction singleton initialisation is not thread safe
> -----------------------------------------------------------------
>
>                 Key: JBAS-5904
>                 URL: https://jira.jboss.org/jira/browse/JBAS-5904
>             Project: JBoss Application Server
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: Transaction Manager (JBossTM)
>    Affects Versions: JBossAS-5.0.0.CR1, JBossAS-4.2.3.GA
>            Reporter: Adrian Brock
>            Assignee: Adrian Brock
>             Fix For: JBossAS-5.0.0.CR2, JBossAS-4.2.4.GA
>
>
> The ClientUserTransaction singleton initialistation is not thread safe:
> private static ClientUserTransaction singleton = null;
> public static ClientUserTransaction getSingleton()
> {
>    if (singleton == null)
>       singleton = new ClientUserTransaction();
>    return singleton;
> }
> Two threads can race to create the singleton which means the ThreadLocal within the class can become
> "masked".
> The construction of the singleton needs moving to static initialisation.

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