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From Boris Granveaud <boris.granve...@europages.com>
Subject Re: How to close persistent non-idle connections after some time
Date Thu, 19 Sep 2013 08:05:00 GMT
Le 18/09/2013 18:07, Oleg Kalnichevski a écrit :
> On Wed, 2013-09-18 at 17:25 +0200, Boris Granveaud wrote:
>
> ...
>
>>> Connection manager's job is to keep track of available persistent
>>> connections and enforce certain time-to-live constraints for those
>>> connections. It is not meant to police busy connections leased by worker
>>> threads.
>>>
>>> Nothing prevents you from creating a custom connection manager, though,
>>> tailored specifically to your application needs.
>> My intention is not to close busy connections but to enforce a maxAge
>> policy when the connection is released to the pool. I see this as
>> complementary to keepalive.
>>
>> Sure I could extend PoolingHttpClientConnectionManager but this implies
>> some code duplication (at least releaseConnection) and reflection to
>> access CPoolEntry.
>>
>> My point is that it is difficult to add this feature externally, but it
>> could be easily integrated as a standard behavior as does Tomcat JDBC
>> Pool for example (see maxAge parameter
>> http://tomcat.apache.org/tomcat-7.0-doc/jdbc-pool.html#Tomcat_JDBC_Enhanced_Attributes).
>>
>> Boris.
>>
> Maybe I am getting too dense with age, but still fail to see a problem
> here. There is already a TTL (total time to live) parameter settable at
> the connection manager level, which prevents connections from being
> re-used beyond a particular time limit.
>
> Besides, I would very much rather add a protected method to
> PoolingHttpClientConnectionManager allowing the expiry time to be
> adjusted by a super class instead of introducing yet another parameter
> that basically duplicates an existing one.

Hum, sorry you are right! I have been confused by the keepalive 
management and I didn't see that the timeToLive parameter is exactly 
what I need. Thanks!

Another point: in Tomcat JDBC pool, there is a validationInterval 
parameter which allows to avoid checking for stale connection each time 
a connection is borrowed from the pool. Basically, this check is 
performed at most at the specified frequency. I have a benchmark where 
the number of requests per second is doubled if I disable the stale 
connection detection, but this seems not a good idea for production. 
Maybe this validationInterval could provide a good compromise between 
performance and reliability, what do you think?

Boris.



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