[jbossts-issues] [JBoss JIRA] Commented: (JBTM-503) Shutdown the ExpiredEntryMonitor when stopping the RecoveryManager

[Mauro Molinari (JIRA)]

    [ https://jira.jboss.org/jira/browse/JBTM-503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12456370#action_12456370 ] 

Mauro Molinari commented on JBTM-503:
-------------------------------------

Hi Andrew,
I was trying to work in this issue to provide you with a patch. I synchronized the start&stop of ExpiredEntryMonitor but I have a problem understanding the lifecycle of the RecoveryManagerImple.

It seems that:
- RecoveryManagerImple.start() is called just from RecoveryManager.startRecoveryManagerThread(), for which I couldn't find any caller
- the ExpiredEntryMonitor is started through ExpiredEntryMonitor.startUp(), which in turn is called by the constructor of RecoveryManagerImple

So, I can't find the correct place where to call ExpiredEntryMonitor.shutdown().

While things work in this way, I would say that it would be safe to call it from RecoveryManagerImple.finalize(), however in this way I would have to explicitely call RecoveryManagerImple.finalize() from my application if I want it to be completely shut down.

If I add a call to ExpiredEntryMonitor.shutdown() into RecoveryManagerImple.stop(boolean), then I would rather expect to find the call to ExpiredEntryMonitor.startUp() in RecoveryManagerImple.start(), so that:
- the RecoveryManagerImple is started and stopped with start() and stop(boolean) by the RecoveryManager
- the ExpiredEntryMonitor is started and stopped sith startUp() and shutdown() by the RecoveryManagerImple
However, as it's not clear to me whether RecoveryManagerImple.start() is actually called and when it is called, I'm not self-confident to move the call to ExpiredEntryMonitor.startUp() from the constructor of RecoveryManagerImple to RecoveryManagerImple.start()...

I would be grateful if you could help me to shed light on this.

> Shutdown the ExpiredEntryMonitor when stopping the RecoveryManager
> ------------------------------------------------------------------
>
>                 Key: JBTM-503
>                 URL: https://jira.jboss.org/jira/browse/JBTM-503
>             Project: JBoss Transaction Manager
>          Issue Type: Feature Request
>      Security Level: Public(Everyone can see) 
>          Components: Recovery
>    Affects Versions: 4.5
>         Environment: Tomcat + Spring + DBCP + JBossJTA
>            Reporter: Mauro Molinari
>            Assignee: Andrew Dinn
>
> When the recovery manager is started, the implementation RecoveryManagerImple starts the ExpiredEntryMonitor.
> When you stop the recovery manager, however, the ExpiredEntryMonitor is not shut down.
> On line 250 of com.arjuna.ats.internal.arjuna.recovery.RecoveryManagerImple there's the line ExpiredEntryMonitor.shutdown() commented out, with a "TODO why?" comment immediately before.
> I don't know exactly what should be the lifecylce of ExpiredEntryMonitor versus that of RecoveryManagerImple, however I think that one of the following should happen:
> - ExpiredEntryMonitor is started when RecoveryManagerImple is started (rather than constructed), so that it is shut down when the RecoveryManagerImple is stopped
> OTHERWISE
> - RecoveryManagerImple provides a way to "dispose" or "disable" it and this includes the shutdown of ExpiredEntryMonitor
> OTHERWISE
> - it is documented that stopping the recovery manager needs the ExpiredEntryMonitor to be stopped too: however, please consider that com.arjuna.ats.internal.arjuna.recovery.ExpiredEntryMonitor.shutdown() throws a NullPointerException if called while the ExpiredEntryMonitor has not been started before and there is no public method to test if it has been started or not; so if I need to write some code that stops the ExpiredEntryMonitor (without knowing if it has been started or not) I have to write some ugly code like:
> {code:java}
> try
> {
>   ExpiredEntryMonitor.shutdown();
> }
> catch(final NullPointerException e)
> {
>   // ExpiredEntryMonitor had not been started
> }
> {code}

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