Sergiu Prodan created HTTPCORE-433:
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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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