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Date: Tue, 1 Oct 2013 14:40:05 +0530
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Subject: Re: Reg: Connection pool
From: Anu Prab <anuprab2@gmail.com>
To: Tomcat Users List <users@tomcat.apache.org>
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On Sep 27, 2013, at 12:21 AM, Anu Prab <anuprab2@gmail.com> wrote:


> On Sep 26, 2013, at 6:02 PM, Christopher Schultz <


> chris@christopherschultz.net> wrote:


>


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>> Hash: SHA256


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>>


>


>> Daniel,


>


>>


>


>> On 9/26/13 9:18 AM, Daniel Mikusa wrote:


>


>>> On Sep 26, 2013, at 2:22 AM, Anu Prab <anuprab2@gmail.com> wrote:


>


>>>


>


>>>> I am using Tomcat version 7.


>


>>>


>


>>> For future reference, please include the exact version of Tomcat you


>


>>> are running.  There are 40+ different versions.


>


>>>


>


>>>> Is it possible to update connection pool properties without


>


>>>> restarting the Tomcat server?


>


>>>


>


>>> Please also include specific details like which connection pool are


>


>>> you using.  There are two included with Tomcat, DBCP and tomcat-jdbc.


>


>>>


>


>>> To give a general answer to your question, you can update some of


>>> the


>


>>> properties through JMX.  It'll depend on the version of Tomcat and


>


>>> which pool you are using as to which properties you can update.


>


>>> Try connecting with jconsole or jvisualvm w/MBeans plugin and see if


>


>>> the properties you need are exposed and editable.


>


>>


>


>> While most properties are not immutable (e.g. you can change their


>


>> values via JMX), changing them usually has no effect because the


>


>> connection pool is not re-initialized when those values change.


>


>


>


> Good point.  It's important to be realistic about what you can do at


> runtime.


>


>


>


>> Perhaps Anu can give us a use case for when this kind of thing would


>


>> be appropriate... what would you want to change during runtime in a


>


>> stable system?


>


>


>


> +1 definitely need more info here.


>


> Dan


>


>


>


> Hi,


>


> Sorry, please ignore my previous mail. My bad.


>


> The Tomcat version I am using is 7.0.40 and the connection pool is


> tomcat-jdbc.


>


> Well, one case would be to increase the maxActive property so that if


> I want to increase this threshold limit, how do I do it?.


Connect with jconsole or jvisualvm.  Navigate to tomcat.jdbc ->
ConnectionPool -> "<your jndi name>" ->
org.apache.tomcat.jdbc.pool.DataSource.  Edit the "maxActive" attribute.


For the most part this works OK.  There were a couple quirks that I noticed
in my quick test.


  - When decreasing maxActive, if you set it lower than the number of
connections already it has no effect until the number of connects drops
below maxActive.


   -   If I tried to grab a connection from the pool and the pool has

already hit maxActive, my request would fail.  However subsequent requests
would succeed.


There could be others, so I'd suggest you test your specific use case in a
controlled environment before trying it in production.


Having said all this, I would agree that it's better to properly size your
connection pool from the start.  If that's not possible, this should work
for you though.


Dan


>Thank you Dan for your inputs.


One more information please:

I have a datasource created through a Servlet and no configuration
information is provided in the context.xml. If some other class within the
same web app wants to do a lookup for this datasource, how to go about
doing this?

- Anu

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