(If the answer differs between Tomcat 7 and Tomcat 8, please note that.) When a SQL exception occurs, often the database connection will be broken and should be evicted from the pool. In our code, we call this "marking the connection for death". We do this because we don't want to set the "testOnReturn" attribute to true to minimize the load on the database server. We set "testOnIdle" which will eventually find and evict stale connections, but maybe not fast enough for a bad connection which is returned to the pool.
My question is whether the "test on return" is done on the same thread as the user, or on a different thread that belongs to the connection pool. If the latter, we wouldn't have to catch the fact that SQL exception has occurred and make sure the connection is evicted from the pool, and maybe would be okay with the extra load on the database server as long as the user time is not affected.
