Hi,
My application's DAO class is employing an injected Hibernate Session
for accessing a MySQL DB. Connection pooling is provided by C3PO.
My understanding is that the Tapestry Hibernate IoC (per thread) service
takes care of closing DB connections under the hood, releasing them back
to the pool, without any explicit requirements inside the DAO. However,
in some cases connections are not being released and eventually MySQL
kills them (after 8 hours or so). This then results in broken pipe
errors within the application which C3PO resolves by recreating the
pool. Obviously not ideal.
One solution is to have C3PO check connections are live when checking
them out from the pool, but before heading down this path I thought it
worth exploring options from a programmatic point of view. Possibly
there is a recommended practice that I'm not following in my DAO class.
In the below DB query you can see two likely leaked connections that
haven't timed out at 300 seconds as configured in C3PO.
MariaDB [mydb]> show full processlist;
+--------+---------+-----------------+---------+---------+------+-------+-----------------------+----------+
| Id | User | Host | db | Command | Time |
State | Info | Progress |
+--------+---------+-----------------+---------+---------+------+-------+-----------------------+----------+
| 298177 | user | localhost:41638 | mydb | Sleep | 2286 |
| NULL | 0.000 |
| 298178 | user | localhost:41640 | mydb | Sleep | 1858 |
| NULL | 0.000 |
| 298179 | root | localhost | mydb | Query | 0 |
init | show full processlist | 0.000 |
| 298232 | user | localhost:42014 | mydb | Sleep | 7 |
| NULL | 0.000 |
| 298233 | user | localhost:42016 | mydb | Sleep | 7 |
| NULL | 0.000 |
| 298234 | user | localhost:42018 | mydb | Sleep | 7 |
| NULL | 0.000 |
| 298235 | user | localhost:42020 | mydb | Sleep | 7 |
| NULL | 0.000 |
| 298236 | user | localhost:42022 | mydb | Sleep | 7 |
| NULL | 0.000 |
| 298237 | user | localhost:42024 | mydb | Sleep | 7 |
| NULL | 0.000 |
| 298238 | user | localhost:42026 | mydb | Sleep | 7 |
| NULL | 0.000 |
| 298239 | user | localhost:42028 | mydb | Sleep | 7 |
| NULL | 0.000 |
+--------+---------+-----------------+---------+---------+------+-------+-----------------------+----------+
11 rows in set (0.00 sec)
Kind regards,
Chris.
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