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https://issues.apache.org/jira/browse/SCXML-112?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ate Douma resolved SCXML-112.
-----------------------------
Resolution: Fixed
With SCXML-196 and SCXML-197 the event handling has been completely refactored
and for the larger part all the above issues have either be resolved or handled
differently.
I'm closing this now as it probably is better to review the new implementation
first and start from there if other/extra functionality is needed.
> Wrong behavior if event is triggered from EventDispatcher
> ---------------------------------------------------------
>
> Key: SCXML-112
> URL: https://issues.apache.org/jira/browse/SCXML-112
> Project: Commons SCXML
> Issue Type: Bug
> Reporter: Ales Dolecek
> Assignee: Ate Douma
> Fix For: 2.0
>
> Attachments: Dispatcher.java, test1.xml, test2.xml
>
>
> Method SCMLExecutor#triggerEvents is synchronized which is too naive way to
> ensure that events are processed in order they arrive.
> Since the callback to EventDispatcher is made by thread that holds lock on
> SCMLExecutor triggering event from the dispatcher allows this thread to
> re-enter the event handling.
> Note: This has nothing to do with multi-threading since there is only one
> thread.
> Simple queue might e sufficient but in multi-threaded application would make
> the first thread to enter #triggerEvents process events from other threads
> queued while the method is running.
> Another approach might be to call EventDispatcher in separate thread,but it
> has it's drawbacks too:
> a) changes single-threaded application into-multithreaded which might break
> assumtions made by unaware user
> b) might start too many threads
> c) Java does not guarantee that threads waiting for lock will get it in same
> order as they arrive => might result in non-deterministic behavior of SCXML
> interpretation
> Possible solutions would be:
> 1) add queue and allow the "first" thread server all events - might be just
> fine since multi-threaded applications might create dedicate thread just for
> SCXML imterpretation
> 2) add queue and block threads after they queue event - so they "wait" until
> execute their event become first in queue
> 3) factor out the queue event queue management and allow for "pluggable"
> strategy
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