[jboss-jira] [JBoss JIRA] (WFLY-3852) EJB @Schedule interleaves timer calls with @AccessTimeout(0)

[Stuart Douglas (JIRA)]

    [ https://issues.jboss.org/browse/WFLY-3852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13002142#comment-13002142 ] 

Stuart Douglas commented on WFLY-3852:
--------------------------------------

I'm saying that the current behaviour is silly. If you want no concurrent access + immediate timeout the spec should require WRITE+AccessTimeout(0), it should not (IMHO) change the behaviour of a read lock if the timeout is set to zero (the whole point of a READ lock is that it does allow concurrent access from multiple threads as long as the WRITE lock is not held). 

I am going to find out if this was actually the intention of the expert group, or if the current version of the spec is just badly worded. 

> EJB @Schedule interleaves timer calls with @AccessTimeout(0)
> ------------------------------------------------------------
>
>                 Key: WFLY-3852
>                 URL: https://issues.jboss.org/browse/WFLY-3852
>             Project: WildFly
>          Issue Type: Feature Request
>          Components: EJB
>    Affects Versions: 8.1.0.Final
>         Environment: Win 7 x64 / i7
>            Reporter: Tibor Digana
>            Assignee: David Lloyd
>            Priority: Critical
>
> Note: The value in @AccessTimeout(value = 0) is not a real timeout. It's a marker skipping scheduler on concurrent Thread.
> Actual: 
> The scheduled method is annotated with @AccessTimeout(0) and @Lock(READ). Very long calls interleave concurrently.
> Expected: 
> The calls should not interleave if and only if @AccessTimeout(0) is used. Does not matter which LockType is used.
> According to the Javadoc
>  "A value of 0 means concurrent access is not permitted."
> In other words the timer should give it up on concurrent Thread. 
> The timer should not wait for read/write lock due to the value in the annotation is not -1.
> In the internal implementation of TomEE server the timer skips scheduling if Lock.tryLock() returns false in this usecase. This can be Read or Write lock - does not matter.
> Don't be confused with WFLY-3430. 
> I think the fix in WFLY-3430 should only go with the annotation @AccessTimeout(0) with whatever LockType. If this annotation is not used then the next call should be concurrent / blocked depending on READ / WRITE LockType, respectively.
> My code:
> @Startup
> @Singleton
> @Lock(READ)
> public class MyTimer {
>  @Schedule(minute = "*", hour = "*", persistent = false, info = "My Timer")
>   @AccessTimeout(0)
>   public void updateByMinutes() {}
> }



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