java.sql.SQLException: Already closed - mysql

Question

We have a webapp running in production on tomcat with a MySQL back-end. All was fine for sometime, then suddenly we started getting this exception java.sql.SQLException: Already closed.
The entire stack trace is:
DEBUG [org.springframework.jdbc.datasource.DataSourceUtils] Fetching JDBC Connection from DataSource
DEBUG [org.springframework.jdbc.datasource.DataSourceUtils] Returning JDBC Connection to DataSource
DEBUG [org.springframework.jdbc.datasource.DataSourceUtils] Could not close JDBC Connection
java.sql.SQLException: Already closed.
at org.apache.commons.dbcp.PoolableConnection.close(PoolableConnection.java:114)
at org.apache.commons.dbcp.PoolingDataSource$PoolGuardConnectionWrapper.close(PoolingDataSource.java:191)
at org.springframework.jdbc.datasource.DataSourceUtils.doReleaseConnection(DataSourceUtils.java:333)
at org.springframework.jdbc.datasource.DataSourceUtils.releaseConnection(DataSourceUtils.java:294)
at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:405)
at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:428)
at com.nokia.analytics.aws.aggregate.service.importer.DBInsert.truncateTable(DBInsert.java:135)
at com.blah.analytics.aggregate.service.importer.AggregateCollector.pullAndInsert(AggregateCollector.java:85)
at com.blah.analytics.aggregate.service.importer.AggregateCollector.call(AggregateCollector.java:96)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1146)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:679)
We are using org.apache.commons.dbcp.BasicDataSource as our datasource. I searched quite a bit but to no avail.
It doesn't occur always and hence is very hard to reproduce. It seems a problem with db connection pooling. Somewhere it was suggested to set this param as negative. Currently we are not changing of those parameters (all have default vals).
What approach should we follow to avoid it?
EDIT:
The relevant code is in (DBInsert.java)
133: String sql = "DELETE FROM "+tableName;
134: logger.debug(sql);
135: this.jdbcTemplate.execute(sql);
(133-135 are line nos. which are specified in the exception)
My datasource config:
<bean id="bisToolDataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url"
value="${url}/blah_db?verifyServerCertificate=false&useSSL=true&requireSSL=true" />
<property name="username" value="${uname}" />
<property name="password" value="${passwd}" />
</bean>

Answer 1

The cause of this problem is connection isn't used in a long time, add testOnBorrow and validationQuery property to your datasource configuration then your application will work fine.
Good luck:)

Answer 2

As user NobodyElse pointed out, the problem was related to connection pooling. I was using org.apache.commons.dbcp.BasicDataSource as datasource. The nature of the application is such that there is spurt of connections at some fixed time in the day and no connections at all for the entire day. So due to this connections in the pool were getting stale and when next day application tried to connect to DB, we were getting this exception.
There are basically two solutions to this:
The one pointed out by NobodyElse, that is to use testOnBorrow; details can be found here
The other solution (which I employed for our app) is to turn off pooling completely. Note do this only when the application is not DB intensive (which was true in our case). So I switched to org.springframework.jdbc.datasource.DriverManagerDataSource. The config for which it seems to be working fine is:
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url"
value="${url}/blah_db?verifyServerCertificate=false&useSSL=true&requireSSL=true" />
<property name="username" value="${uname}" />
<property name="password" value="${passwd}" />
</bean>