Fisheye and Crucible is using BoneCP 0.7.1.RELEASE as a data base connection pool. In this version when the connection is returned to the pool statements are not closed. According to JDBC API statements should be closed when a connection is closed (= returned to the pool).

9.4.4 Closing Connection Objects
An application calls the method Connection.close to indicate that it has finished
using a connection. All Statement objects created from a given Connection object
will be closed when the close method for the object is called.

It is expected from a database pool manager to perform this cleaning: https://github.com/brettwooldridge/HikariCP/wiki/Pool-Analysis

It seems this bug is a specially affecting the application performance when used with MySQL. The MySQL driver connection object (com.mysql.jdbc.JDBC4Connection) contains a reference to all open statements. This can eventually cause an OOM.

As a workaround for MySQL is to add

dontTrackOpenResources=true

parameter to the MySQL connection URL:

jdbc:mysql://[host][:port]/[database]?dontTrackOpenResources=true

Issue was observed on MySQL and Oracle but most likely affects other DBs too.