Hello,
I'm using Tomcat 7.0.34 via TomEE 1.5.1 with MySQL. I noticed a memory
leak in my web application which uses jdbc connection pooling with
Tomcat's jdbc-pool.
The com.mysql.jdbc.JDBC4Connection class has a field named
"openStatements" which holds, as you can imagine, open sql statements.
This structure grows continuously over time and no statements are ever
released. I stepped into my code to verify that I closed opened
statements and it is the case.
Digging some more, I downloaded Tomcat's source and it seems that
jdbc-pool discards all calls to java.sql.Statement.close() in
StatementDecoratorInterceptor#invoke(Object proxy, Method method,
Object[] args)
I see what could be a bug in StatementCache#closeInvoked() which is
called by the above method. Here is the code with my own comments added:
@Override
public void closeInvoked() {
boolean shouldClose = true;
if (cacheSize.get() < maxCacheSize) {
// omitted for brievety
}
closed = true;
// [1] I think "delegate = null" is done too soon
delegate = null;
if (shouldClose) {
// check its body below
super.closeInvoked();
}
}
// This is super.closeInvoked()
public void closeInvoked() {
if (getDelegate()!=null) {
// never true when coming from
// StatementCache#closeInvoked()
// because of [1]
try {
getDelegate().close();
}catch (SQLException ignore) {
}
}
closed = true;
delegate = null;
}
Regards,
Bertrand
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