Maximum number of DB connections in pool

[Paolo]

Dear All,

I would like to submit you a fairly frequent problem in our cadmus.eui.eu repository.

Our DSpace 5.2 installation works as a front-end on a virtual machine with 4 CPU and 8 GB RAM and the back-end with Oracle db on the Oracle enterprise installation in our University ICT environment. The access to the DMZ, where the front-end is located, is managed by linux server with an Apache httpd.conf configuration apparently not limited by the number of simultaneous connections. Our problem is the number of connections to the db that quite frequently reach 200 as configured in dspace.cfg.

#Maximum number of DB connections in pool

db.maxconnections = 200

Unfortunately, despite the fact that the 200 connections are inactive, they blocked access to the server forcing tomcat to restart.

Please find attached the result of an SQL query for inactive connections

Any suggestions or previous experience in this regard are extremely welcome.

Best Regards

Paolo Baglioni

Library Systems Analyst

European University Institute

50014 Firenze ITALY

[Alan Orth]

Dear Paolo,

We had similar problems that were completely resolved by switching to a pool managed in Tomcat via JNDI, rather than via DSpace itself. We are using PostgreSQL, but the idea would be the same for Oracle. See my detailed dspace-tech mailing list post in December, 2017¹. Also, see the commits to our site's infrastructure repository on GitHub² for some insight on the Tomcat changes required. Lastly, we ended up setting up two pools³: one for the REST API and another for XMLUI and the others.

Hope that helps,

¹ http://dspace.2283337.n4.nabble.com/Notes-on-PostgreSQL-connection-pooling-with-a-Tomcat-JNDI-resource-td4687149.html

² https://github.com/ilri/rmg-ansible-public/commit/1959d9cb7a0e7a7318c77f769253e5e029bdfa3b

³ https://github.com/ilri/rmg-ansible-public/blob/master/roles/dspace/templates/tomcat/server-tomcat7.xml.j2#L50

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[Alan Orth]

Dear Paolo,

I should also add the some of the benefits of managing the pool outside of Tomcat is that they can be shared across web applications (rather than having one per web application context), you can do connection re-use, connection validation, etc.

Regards,