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From "Jeff Roberts" <j...@rcshome.com>
Subject (more info) 2.0.2 - maxConnectionsPerHost and maxTotalConnections
Date Wed, 25 Jan 2006 18:54:39 GMT
OK, I think I understand what we're TRYING to do better now, let me take a shot at explaining.

The defaults for maxConnectionsPerHost and maxTotalConnections are 2 and 20, so I think that's
where we got the *10 multiplier.  We believe the multiplier is supposed to account for the
number of http servers we're forwarding requests to, which in our case is only one Apache
server, so we think we could do without the *10 - please advise if any of that's wrong.

The one Apache server is load balancing via mod_jk to 1 or more Tomcat servers.  The cachesize
parameter in the workers.properties is set to 10, but we're trying to leave 2 slots there
for other requests besides the ones this particular server handles, which leaves us 8 slots
per server.

So we're setting maxConnectionsPerHost to 8, and currently we're setting maxTotalConnections
to 8*10, although we think the *10 may be unnecessary.  Now we're trying to account for there
being more Tomcats, so we're planning to set maxConnectionsPerHost to 8*num_tomcats and maxTotalConnections
to 8*num_tomcats as well.

Does that make any sense?
J. Jeff Roberts
(859) 552-5806

----- Original Message ----- 
From: 'Jeff Roberts' <jeff@rcshome.com>
To: httpclient-user@jakarta.apache.org
Sent: Wed, 25 Jan 2006 09:18:30
Subject: Fwd: 2.0.2 - maxConnectionsPerHost and maxTotalConnections

I've picked up some code that everyone suddenly disavows all knowledge of...you know how that
goes. :-)

We are creating a MultiThreadedHttpConnectionManager, setting maxConnectionsPerHost to 8 and
maxTotalConnections to 8 * 10.  That object is passed to the constructor for HttpClient. 
We then receive requests, which we route to an Apache server, which is load balancing to 1
or more Tomcats via mod_jk.

I am told that someone fiddled around and found the 8/80 setting works well if we're "balancing"
over only 1 Tomcat, but that they think we should multiply one or both of the properties by
the number of Tomcats as we add servers.  No one seems to know where the "* 10" in the call
to maxTotalConnections came from, or whether we still need it if we multiply the 8 by the
number of Tomcats.

1. If any of that made sense, does anyone have a clue if we're setting these parameters correctly,
and if either the 8 or the "* 10" makes any sense?

2. Does it sound right to multiply one or both by the number of Tomcats?

3. Can I call setMaxConnectionsPerHost() and setMaxTotalConnections() at any time?  While
requests are cranking through, in other words?  Can I call them both with a larger and a smaller
number than the current setting without problems, as Tomcats are added or removed?

Any info much appreciated.

J. Jeff Roberts 
(859) 552-5806 

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