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From "Jeff Genender (JIRA)" <>
Subject [jira] [Created] (CAMEL-4345) Synchronized code causes long delays and hangs for big applications especially with Blueprint
Date Thu, 18 Aug 2011 05:19:27 GMT
Synchronized code causes long delays and hangs for big applications especially with Blueprint

                 Key: CAMEL-4345
             Project: Camel
          Issue Type: Bug
          Components: camel-core
    Affects Versions: 2.8.0
         Environment: Linux and Mac multicore machines
            Reporter: Jeff Genender

The DefaultCamelContext uses synchronized "endpoints" which ends up ultimately extending a
LinkedHashMap through the LRUCache.  The LinkedHashMap is obviously not thread safe, so it
requires synchronized guards when accessing the endpoints object.  This especially happens
in the getEndpoint(s) calls in the DefaultCamelContext.  In large systems with lots of routes
and on multicore systems, dynamically created routes (and many routes) can cause long delays
and hang for long times since route creation and the starting of the camel route can occur
in unison with synchronization.  In a blueprint container, such as Karaf, this can cause timeouts
on the bundle and camel routes will appear to hang indefinately.  Thread dumps show the hangs
occur on the synchronized call in getEndpoint(s).  The fix for this is to use concurrent apis
as much as possible and remove the synchronized code.  I refactored the LRUCache/LRUSoftCache
to use Google's ConcurrentLinkedHashMap (ASL2 License
and removed the synchronized code that locks the endpoints object.  This should remove the
hangs since the locks are no longer required.  Since COncurrentLinkedHashmap is not OSGi ready,
I have shaded the classes in core.  On my executions, all unit tests pass with this refactoring
using the concurrent code.  This should speed up Camel on multicore systems that have lots
of routes.

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