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From "Oleg Kalnichevski (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HTTPCORE-469) Use ReentrantReadWriteLock in AbstractConnPool
Date Mon, 19 Jun 2017 08:54:00 GMT

     [ https://issues.apache.org/jira/browse/HTTPCORE-469?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Oleg Kalnichevski updated HTTPCORE-469:
           Labels: stuck volunteers-wanted  (was: )
    Fix Version/s: Future

I looked at the possibility of replacing {{ReentrantLock}} with {{ReentrantReadWriteLock}}.
Most of connection pool methods would require write access. Only very few methods could be
potentially considered read-only and would benefit from a separate read lock. I also suspect
write lock acquisition with {{ReentrantReadWriteLock}} might be somewhat more expensive than
with {{ReentrantLock}} thus making the pool slower when leasing / releasing connection. 

I am more inclined to put my efforts into HTTPCORE-390. Unless someone else steps in and volunteers
to do the necessary research and development I am leaning toward closing this issue as WONTFIX.


> Use ReentrantReadWriteLock in AbstractConnPool
> ----------------------------------------------
>                 Key: HTTPCORE-469
>                 URL: https://issues.apache.org/jira/browse/HTTPCORE-469
>             Project: HttpComponents HttpCore
>          Issue Type: Improvement
>          Components: HttpCore
>            Reporter: Matt Nelson
>            Assignee: Oleg Kalnichevski
>            Priority: Minor
>              Labels: stuck, volunteers-wanted
>             Fix For: Future
> AbstractConnPool is currently using a {{ReentrantLock}} which has to lock for read and
write operations. Switching to {{ReentrantReadWriteLock}}[1] and read locks for the stats/getters
methods would reduce the possibility for instrumentation[1] to cause contention. Another option
would be {{StampedLock}}[3] if the compile target is 1.8.
> [1] https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/ReentrantReadWriteLock.html
> [2] https://github.com/dropwizard/metrics/blob/v3.2.2/metrics-httpclient/src/main/java/com/codahale/metrics/httpclient/InstrumentedHttpClientConnectionManager.java#L63-L95
> [3] https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/StampedLock.html

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