Differences

This shows you the differences between two versions of the page.

--- mysql:problemresolution [2013/07/23 15:50] – rlunaro
+++ mysql:problemresolution [2013/10/04 10:10] (current) – removed rlunaro
@@ Line 1: / Line 1: @@
-====== Problem Resolution ======
-===== Problem =====
-<code>
-/20 01:38:26 hibernate.util.JDBCExceptionReporter     - Communications link failure
-The last packet successfully received from the server was 7.202.618 milliseconds ago.  The last packet sent successfully to the server was 7.202.618 milliseconds ago.
-</code>
-===== Some tools =====
-This will show you the current connections:
-<code>
-show status like '%onn%';
-</code>
-Example of output:
-<code>
-mysql> show status like '%onn%';
-+--------------------------+-------+
-| Variable_name            | Value |
-+--------------------------+-------+
-| Aborted_connects         | 0     |
-| Connections              | 50    |
-| Max_used_connections     | 9     |
-| Ssl_client_connects      | 0     |
-| Ssl_connect_renegotiates | 0     |
-| Ssl_finished_connects    | 0     |
-| Threads_connected        | 8     |
-+--------------------------+-------+
-rows in set (0.00 sec)
-</code>
-Pay attention to the data "Threads_connected", which is similar to the result of the ''show processlist''.
-===== What are the maximum connections that mysql can have =====
-<code>
-show variables like "max_connections";
-</code>
-===== What are the maximum timeout that a connection will be kept open =====
-<code>
-mysql> show variables like '%imeout%';
-+----------------------------+----------+
-| Variable_name              | Value    |
-+----------------------------+----------+
-| connect_timeout            | 10       |
-| delayed_insert_timeout     | 300      |
-| innodb_lock_wait_timeout   | 50       |
-| innodb_rollback_on_timeout | OFF      |
-| interactive_timeout        | 28800    |
-| lock_wait_timeout          | 31536000 |
-| net_read_timeout           | 30       |
-| net_write_timeout          | 60       |
-| slave_net_timeout          | 3600     |
-| wait_timeout               | 28800    |
-+----------------------------+----------+
-rows in set (0.00 sec)
-</code>
-===== Maybe c3p0 has the solution =====
-Eventually I've implemented a configuration in the connection pooling mechanism to:
-  * verify the connection when it enters into the pool
-  * put a timeout to this connection, releasing it after this period
-This will prevent the case when a connection is held but the JDBC driver drops out.
-My config parameters:
-<code xml>
-    <property name="minPoolSize" value="2"/>
-    <property name="maxPoolSize" value="4"/>
-    <property name="initialPoolSize" value="1"/>
-    <!-- good for mysql. For oracle, select * from dual could be good enough -->
-    <property name="preferredTestQuery" value="select 1"/>
-    <property name="testConnectionOnCheckin" value="true"/>
-    <property name="idleConnectionTestPeriod" value="60"/>
-</code>
-And where I've taken them:
-http://www.mchange.com/projects/c3p0/