I'm running a Scala application on this software stack:
Mac OS X 10.6.8 Snow Leopard
MySQL 5.1.46
Java 1.6.0_65
Scala 2.11.2
ConnectorJ 5.1.33
HikariCP 2.1.0
Slick 2.1.0
I cannot get why open connections to MySQL keep staying open even after shutting the Scala app down. The only correct aspect is that the Threads_connected drops from 16 down to 1 (that is the console from which I'm executing the 'show status' command.
mysql> show status like '%onn%';
+--------------------------+-------+
| Variable_name | Value |
+--------------------------+-------+
| Aborted_connects | 0 |
| Connections | 77 |
| Max_used_connections | 19 |
| Ssl_client_connects | 0 |
| Ssl_connect_renegotiates | 0 |
| Ssl_finished_connects | 0 |
| Threads_connected | 1 |
+--------------------------+-------+
7 rows in set (0.00 sec)
The strange thing is I always see the open connections to the DB growing up by the maximum number of open connections set in the connection pool (HikariCP maximumPoolSize) every time I run the app hence I can state the connections are never given back to the connection pool for reuse.
According to Slick documentation using
db withSession { implicit session =>
/* entering the scope, getting 1 conn from the pool */
/*
do something within the session using the connection I've gotten
*/
}
/* here I'm out of the 'withSession' scope, and the
connection should be released */
will take a connection from the pool when entering its scope and will release it just out of the scope
Am I doing something wrong or did I get something wrong about connection pool usage on this software stack?
Connections is a counter of how many connection attempts have been made since the last time you started mysqld. This counter always increases; it does not decrease when the connections end.
That counter is not the number of current connections -- that's Threads_connected.