Do I need to use C3P0 pooling library in my (grail

问题:

I am not familiar at all with connection pooling library. I've just discovered it through this blog article) and I am not sure that I should use one in my web application based on grails/hibernate/mysql.

So my question is simple : in which situations would you suggest to integrate a connection pooling library into a grails application? Always, Never or only over some connections threshold?

P.S. : If you have ever used successfully C3P0 in your web application, I will greatly appreciate to hear your feedback (in terms of visible positive effects).

回答1:

Regardless of which pooling implementation, you should use a connection pool always in your web application. Open a connection with the database is a very expensive task and being able to reuse a already existing and idle connection greatly improves your site performance.

A connection can be managed by the application server (Tomcat, JBoss, Glassfish...) or by your application. The latter is easier to setup but it's hard to customize per deployment. Configuring a connection pool on the application and setting your site to consume it makes easy to the fine tune the connection pool parameters, like: minimum connections to keep open, max idle time and so on.

回答2:

My experience with this is pretty limited, but I ended up using C3P0 for the simple reason that Hibernate does not seem to handle MySQL restarts. I got a "Broken pipe" every morning because our hosting service restarted MySQL every night.

I googled it and the only advice I could find was to use... the connection pool of the app server or C3P0. For me, the latter works just fine.

回答3:

I always use a connection pool for two reasons:

1. Because opening connections is an expensive operation
2. It's dead-simple to set one up to work transparently, so there's no real advantage to not using one.

If you're already using hibernate, just modify your hibernate.cfg.xml's connection.provider_class to use org.hibernate.connection.C3P0ConnectionProvider and throw the c3p0 jar file into your servlet's WEB-INF/lib folder. Done.

If you're using JNDI and a GlobalNamingResources declaration, modify the type property to point to com.mchange.v2.c3p0.ComboPooledDataSource and throw the c3p0 jar into Tomcat's /lib folder. Done.

回答4:

C3P0 is a very decent pool but I would still recommend to use the connection pool of your app server or servlet engine and to configure Grails to use it via a regular DataSource. Use a stand-alone connection pool when you can't do that (in which case C3P0 is a good choice).