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From "Sergiu Prodan (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HTTPCORE-433) Setting validateAfterInactivity to 1ms increases lock contention in AbstractConnPool
Date Mon, 19 Sep 2016 14:17:20 GMT
Sergiu Prodan created HTTPCORE-433:
--------------------------------------

             Summary: Setting validateAfterInactivity to 1ms increases lock contention in
AbstractConnPool
                 Key: HTTPCORE-433
                 URL: https://issues.apache.org/jira/browse/HTTPCORE-433
             Project: HttpComponents HttpCore
          Issue Type: Bug
          Components: HttpCore
    Affects Versions: 4.4.4
            Reporter: Sergiu Prodan


This issue was observed after upgrading to httpclient v4.5.2 and httpcore v4.4.4. 

When configuring the PoolingHttpClientConnectionManager, I have set validateAfterInactivity
to 1ms as this is the only way of maintaining the old behaviour, i.e. checking every connection
if is stale before using it.

I have observed a performance degradation under high load when the httpclient is shared between
multiple threads. 

After taking a thread dump, one thing that got my attention was several threads waiting for
same ReentrantLock instance while trying to AbstractConnPool#getPoolEntryBlocking
/AbstractConnPool#release. The ReentrantLock instance in question was owned by another thread
performing CPool#validate.

It seems to me that performing this stale check inside the region protected by this lock is
unnecessary and also induces a big performance hit when using the httpclient from multiple
threads.

I've atached a thread dump of a test application that reproduces this behaviour. ReentrantLock
in question in this thread dump is 0x0000000706e8b9a8 and is owned by Thread-4



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