tech oriented notes to self and lessons learned
tomcat-jdbc is a relatively new entrant to the Java JDBC connection pool game. It’s been designed to be a drop-in replacement for commons-dbcp.
Many of the popular Java connection pool implementations have become quite stagnant over the years, so it’s nice to see someone make a fresh start in this domain. tomcat-jdbc code base is small and has minimal dependencies. It has configurable connection validation (validation policy, query and intervals) and enables automatically closing connections after they reach a configurable maximum age.
Some time ago, we started having problems with a near end-of-life legacy application that was migrated to a new environment. The application was a standalone Java app that used commons-dbcp as its JDBC connection pool implementation. After the migration, MySQL connections started failing occasionally. This appeared to happen with a somewhat regular interval of a few hours. Since tomcat-jdbc API is compatible with commons-dbcp we were able to replace the connection pool without any code changes and configure the new pool to automatically close connections once they had been open for a certain period of time. This turned out to be an effective and nonintrusive workaround for the issue.
I hope the Tomcat development team would more actively promote using tomcat-jdbc also outside of Tomcat. The pool implementation doesn’t currently seem to be available as a separate download or from Maven central, which is likely to hinder its adoption.