List not disconnected or not properly disconnected Database-connections - sql-server

Question

I'm using a dynamic Java Web Application (Tomcat 8.0.15, Java EE 7 Web) with a SQL Server 2008 and after getting the warning/exception
WARNING [Tomcat JDBC Pool Cleaner[510210701:1481713957404]] org.apache.tomcat.jdbc.pool.ConnectionPool.suspect Connection has been marked suspect, possibly abandoned PooledConnection[net.sourceforge.jtds.jdbc.JtdsConnection#510fc080][67975 ms.]:java.lang.Exception
quite too often I wonder somewhere in the depths of my source code I forgot to disconnect a JDBC or Hibernate Connection to the database. I'd like to list them somehow.
A regular
static
{
try {
Context context = new InitialContext ();
dataSource = (DataSource) context.lookup("java:comp/env/jdbc/sqlserv");
} catch (NamingException ex) {
Logger.getLogger(Basisverbindung.class.getName()).log(Level.SEVERE, null, ex);
}
}
does that job and in my hibernate.cfg.xml it's the same:
<property name="hibernate.connection.datasource">java:comp/env/jdbc/sqlserv</property>
I looked through Stackoverflow and found only a few entries which I consulted already (and even upvoted):
Tomcat 7 connection pooling error
WebApp (Tomcat-jdbc) Pooled DB connection throwing abandon exception
https://dba.stackexchange.com/questions/114759/tomcat7-jdbc-connection-pool-connection-has-been-abandoned
But the issue persists or comes up again after a while so I would like to find a way how to track down where I forgot to close the connection. On my Tomcat there's also a PSI Probe running telling me there are coming up some errors in the requests and sometimes maxing out the Response time.
I see a nice list of requests there but don't know which ones are abandoned.
The ActivityMonitor in the SQL-Server Management Studio is not of too much help either it lists quite a few processes of which I know they are closed (or well, should be).
What's the best way to analyze that kind of problem?

Answer 1

What you really want to do is enable "abandoned connection" tracking and reporting.
You didn't say which of Tomcat's JDBC DataSource pools you were using (there are two), but they are configured similarly:
commons-dbcp2-based: logAbandoned=true, removeAbandonedOnBorrow=true
tomcat-jdbc-based: logAbandoned=true, removeAbandoned=true
I always recommend everyone run with a maximum pool size of 1 in development environments. This will help you identify pool leakage very quickly, plus catch any potential deadlocks you may have planted in your code.