Unusually large number of blocking threads

>
> Hi,
>
>  We have an urgent issue in production. When the application is under load
> requests to generate the xform sometimes do not come back and the threads
> associated with those request keep on waiting for a lock monitor to become
> available. I am still digging but it appears there may be an issue with
> MemoryCacheImpl. I looked at the source code and no changes have been made
> to this class in a while and hence I am not sure why we would be the only
> ones with the issue. Looking at the class it does look like a couple of
> methods are not threadsafe (findAny, getMax etc....) but I am really not
> sure if this is really the issue. Any thoughts out there?
>
> Here is a thread that seems to hang on to a lock:
>
> "http-172.17.0.66-1443-46" daemon prio=10 tid=0x00002aab4c80d800 nid=0x643d
> waiting for monitor entry [0x000000004a9a7000]
>   java.lang.Thread.State: BLOCKED (on object monitor)
>        at org.orbeon.oxf.cache.MemoryCacheImpl.findValid(MemoryCacheImpl.java:124)
>        - locked <0x00002aaabea27c88> (a org.orbeon.oxf.cache.MemoryCacheImpl)
>        at org.orbeon.oxf.util.XPathCache.getXPathExpression(XPathCache.java:367)
>        at org.orbeon.oxf.util.XPathCache.getXPathExpression(XPathCache.java:276)
>        at
> org.orbeon.oxf.processor.pipeline.choose.ConcreteChooseProcessor.start(ConcreteChooseProcessor.java:193)
>        at
> org.orbeon.oxf.processor.pipeline.PipelineProcessor$5.run(PipelineProcessor.java:647)
>        at
> org.orbeon.oxf.processor.ProcessorImpl.executeChildren(ProcessorImpl.java:526)
>        at
> org.orbeon.oxf.processor.pipeline.PipelineProcessor.start(PipelineProcessor.java:644)
>        at org.orbeon.oxf.pipeline.InitUtils.runProcessor(InitUtils.java:90)
>        at
> org.orbeon.oxf.webapp.ProcessorService.service(ProcessorService.java:100)
>        at
> org.orbeon.oxf.servlet.OrbeonServletDelegate.service(OrbeonServletDelegate.java:138)
>        at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
> .......
> Here is one of 50  typical threads that is waiting forever to get that lock:
>
> "http-172.17.0.66-1443-258" daemon prio=10 tid=0x000000005125b000 nid=0x66d0
> waiting for monitor entry [0x0000000068985000]
>   java.lang.Thread.State: BLOCKED (on object monitor)
>        at org.orbeon.oxf.cache.MemoryCacheImpl.findValid(MemoryCacheImpl.java:124)
>        - waiting to lock <0x00002aaabea27c88> (a
> org.orbeon.oxf.cache.MemoryCacheImpl)
>        at org.orbeon.oxf.util.XPathCache.getXPathExpression(XPathCache.java:367)
>        at org.orbeon.oxf.util.XPathCache.getXPathExpression(XPathCache.java:276)
>        at
> org.orbeon.oxf.processor.pipeline.choose.ConcreteChooseProcessor.start(ConcreteChooseProcessor.java:193)
>        at
> org.orbeon.oxf.processor.pipeline.PipelineProcessor$5.run(PipelineProcessor.java:647)
>        at
> org.orbeon.oxf.processor.ProcessorImpl.executeChildren(ProcessorImpl.java:526)
>        at
> org.orbeon.oxf.processor.pipeline.PipelineProcessor.start(PipelineProcessor.java:644)
>        at org.orbeon.oxf.pipeline.InitUtils.runProcessor(InitUtils.java:90)
>        at
> org.orbeon.oxf.webapp.ProcessorService.service(ProcessorService.java:100)
>        at
> org.orbeon.oxf.servlet.OrbeonServletDelegate.service(OrbeonServletDelegate.java:138)
>        at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
>
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>
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>