Get connection pool status with grails - grails

Question

I have a webservice built with grails that connects to a MySQL database. Since i upgraded to 2.4.3 I've had problems with the connectionpool not releasing the connections, resulting in an exception:
org.apache.tomcat.jdbc.pool.PoolExhaustedException: [http-bio-8080-exec-216] Timeout: Pool empty. Unable to fetch a connection in 30 seconds, none available[size:50; busy:50; idle:0; lastwait:30000]
This is my Datasources.groovy
dataSource {
url = "jdbc:mysql://..."
username = "xxx"
password = "xxx"
pooled = true
properties {
maxActive = 50
maxAge = 10 * 60000
timeBetweenEvictionRunsMillis = 5000
minEvictableIdleTimeMillis = 60000
numTestsPerEvictionRun=3
testOnBorrow=true
testWhileIdle=true
testOnReturn=true
validationQuery="SELECT 1"
}
}
dataSource_survey {
url = "jdbc:mysql://..."
username = "xxx"
password = "xxx"
pooled = true
properties {
maxActive = 50
maxAge = 10 * 60000
timeBetweenEvictionRunsMillis = 5000
minEvictableIdleTimeMillis = 60000
numTestsPerEvictionRun=3
testOnBorrow=true
testWhileIdle=true
testOnReturn=true
validationQuery="SELECT 1"
}
}
I've read grails JIRA and some people seem to have similar problems. But I haven't been able to fix it with the information provided there.
Accessing the status of the connectionpool would help debugging a great deal. How can I check the status of the connectionpool to see how many connections are idle/busy during runtime?

Answer 1

The connection pool is registered as a javax.sql.DataSource but that interface only has methods for getting a Connection (one with username/password and one without), accessing a log writer, and getting/setting the login timeout. Everything else is left to the vendor to decide, and there's very little commonality between vendors in their methods for configuring pools initially, and working with and monitoring them throughout the app run.
So you really need to find out which library is used for the pool and use their API. That would ideally be as simple as accessing the dataSource bean (that's easy, just dependency-inject it into a service/controller/etc. like any bean - as a class-scope field, in this case def dataSource) and printing its class name. But we wrap the datasource in a few proxies to add some important behaviors, so it not easy to access
You're in luck though - for cases like this, we leave the original unproxied instance alone and register it as the dataSourceUnproxied bean which you can also dependency-inject (just don't access any of its connections, only information).
For a long time we used commons-pool to manage datasources, but a while back we switched to the Tomcat JDBC Pool because benchmark tests showed that it's faster than any other they looked at (including C3P0), and its configuration methods are based on commons-pool's, so it was basicallly a drop-in replacement with a significant performance boost and more configurability.