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From Jakob Korherr <jakob.korh...@gmail.com>
Subject Re: 100% CPU Usage and blocking concurrent Threads when using t:saveState
Date Thu, 10 Dec 2009 09:34:32 GMT
I agree with Mario. It really seams llike the internal structure of the
TreeMap is destroyed, thus ending in some infinite loop and causing 100%
CPU.

Shouldn't we generally synchronize those Maps or use ConcurrentMaps?

Regards,

Jakob Korherr

2009/12/10 Mario Ivankovits <mario@ops.co.at>

>   For me, this clearly looks like concurrent usage of the request map.
>
> All the servlet scopes (session, request, …) are not thread safe and one
> has to assure that they are not accessed at the same time by multiple
> threads.
>
>
>
> This turns out to be hard as e.g. there is no "standard" how to synchronize
> against the session map. As a side note: I often wonder why this does not
> lead to much more problems in the wild …
>
>
>
> Anyway, in your case it seems the internal datastructure of the request map
> is damaged - which in fact is strange as I do not know when the request map
> will be accessed by multiple threads.
>
>
>
> Sorry that this is not a solution, but it should give you a clue where to
> look next …
>
>
>
> Ciao,
>
> Mario
>
>
>
> *Von:* Jan Baudisch [mailto:jan.baudisch@gmx.net]
> *Gesendet:* Donnerstag, 10. Dezember 2009 08:02
> *An:* MyFaces Discussion
> *Betreff:* 100% CPU Usage and blocking concurrent Threads when using
> t:saveState
>
>
>
> Hello MyFaces Community,
>
>
>
> we are using MyFaces 1.2.0 with Tomahawk Sandbox  1.1.5 and have the
> problem, that once in a while we get 100% CPU Usage and blocking concurrent
> threads because of using t:saveState
>
>
>
> A thread dump shows that the threads always stops at
>
>
>
>         at java.util.TreeMap.put(TreeMap.java:545)
>
>         at
> org.apache.myfaces.custom.redirectTracker.RedirectTrackerManager.addSaveStateBean(RedirectTrackerManager.java:306)
>
>         at
> org.apache.myfaces.custom.redirectTracker.RedirectTrackerVariableResolver.resolveVariable(RedirectTrackerVariableResolver.java:50)
>
>
>
> (The complete thread dump is attached). The problem shows up on one system
> with heavy concurrent usage and JxBrowser as client.
>
>
>
> After we kill these threads using Lambda Probe, the CPU Usage normalizes.
>
>
>
> The problem occurs in that method:
>
>
>
> ...
>
>     public void addSaveStateBean(String expressionString, Object value)
>
>     {
>
>         if(log.isDebugEnabled())
>
>             log.debug("addSaveStateBean: " + expressionString + " value=" +
> value);
>
>         requestBeanMap.put(expressionString, value);
>
>     }
>
> ...
>
>     private final Map requestBeanMap = new TreeMap(); ...
>
>
>
> As the problem is really severe for us, any hints are highly appreciated.
>
>
>
> Many thanks in advance,
>
> -- Jan
>
>
>

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