Tomcat JDBC pool - auto reconnect

[Vasily Kukhta <v....@gmail.com>]

Hi friends,

I have a question regarding the ability of Tomcat JDBC pool to reconnect
automatically to a database in case of temporarily network failures.

I'm developing a high-load application which uses Oracle 11g database. It
may happen that the DB can become unavailable for several minutes - it is
located in another geographic region, so network failures can happen
sometimes and the DB becomes unresponsive. Can the Tomcat JDBC pool
automatically reconnect to the DB when it becomes online again? Is this
done by default or it should be configured somehow?

Thank you in advance!

Best regards,
Vasily Kukhta.

Re: Tomcat JDBC pool - auto reconnect

[Daniel Mikusa <dm...@pivotal.io>]

On Fri, Oct 10, 2014 at 9:51 AM, Vasily Kukhta <v....@gmail.com> wrote:

> Hi friends,
>
> I have a question regarding the ability of Tomcat JDBC pool to reconnect
> automatically to a database in case of temporarily network failures.
>
> I'm developing a high-load application which uses Oracle 11g database. It
> may happen that the DB can become unavailable for several minutes - it is
> located in another geographic region, so network failures can happen
> sometimes and the DB becomes unresponsive. Can the Tomcat JDBC pool
> automatically reconnect to the DB when it becomes online again?


In a manner of speaking.  You can configure the pool to test connections,
remove bad ones and try to replace them with new, good connections.  See
"validationQuery", "testWhileIdle and "testOn*" here.

  http://tomcat.apache.org/tomcat-7.0-doc/jdbc-pool.html#Common_Attributes

The trick is that the pool doesn't know when your DB comes back online, so
you might get exceptions while the DB is offline (especially if it's down
for a long time).  It will start talking again once the DB comes back
online though.


> Is this done by default or it should be configured somehow?
>

No.  You need to set a validation query and set at least one of the "test*"
attributes to "true".

Dan


>
> Thank you in advance!
>
> Best regards,
> Vasily Kukhta.
>