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From "Sergiu Prodan (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HTTPCORE-433) Setting validateAfterInactivity to 1ms increases lock contention in AbstractConnPool
Date Mon, 19 Sep 2016 14:30:20 GMT

    [ https://issues.apache.org/jira/browse/HTTPCORE-433?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15503642#comment-15503642
] 

Sergiu Prodan edited comment on HTTPCORE-433 at 9/19/16 2:29 PM:
-----------------------------------------------------------------

Added two screenshots of thread visualisation when making requests from 10 threads. 

PoolingHttpClientConnectionManager#setValidateAfterInactivity set to 1 and 2000 respectively


was (Author: sergiuprodan):
Thread visualisation when making requests from 10 different threads. PoolingHttpClientConnectionManager#setValidateAfterInactivity
set to 1

> 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
>         Attachments: httpclient_thread_dump, threads_when_inactivity_set_to_1.png, threads_when_inactivity_set_to_2000.png
>
>
> 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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