mysql 8小时问题的解决方法

转发： 别看是英文 ，写的很好 ，才转

Use Hibernate + MYSQL database development, link timeout problem:

com.mysql.jdbc.CommunicationsException: The last packet successfully received from the server was58129 seconds ago.The last packet sent successfully to the server was 58129 seconds ago, which is longer than the server configured value of ‘wait_timeout‘. You should consider either expiring and / or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector / J connection property ‘autoReconnect = true‘ to avoid this problem.

Checked and the original problem is the mysql timeout if the connection idle for 8 hours (8 hours, no database operations), mysql will automatically disconnect to restart the tomcat.

The solution:

One. If you do not hibernate, then adding in the connection url parameter: autoReconnect = true

jdbc.url = jdbc: mysql: / / ipaddress: 3306/database? autoReconnect = true & autoReconnectForPools = true

Two. With hibernate, then add the following attributes: 
<property name="connection.autoReconnect"> true </ property> 
<property name="connection.autoReconnectForPools"> true </ property> 
<property name="connection.is-connection-validation-required"> true </ property>

III. If still using c3p0 connection pool: 
<property name="hibernate.c3p0.acquire_increment"> 1 </ property> 
<property name="hibernate.c3p0.idle_test_period"> 0 </ property> 
<property name="hibernate.c3p0.timeout"> 0 </ property> 
<property name="hibernate.c3p0.validate"> true </ property>

IV. The worst solution

Using the Connector / J MySQL database connection, the program will run a long time after the reports the following error:

Communications link failure, The last packet successfully received from the server was *** millisecond ago.The last packet successfully sent to the server was *** millisecond ago.

One error will prompt you to change wait_timeout or use the Connector / J‘s autoReconnect property to avoid the error.

Then check out some information, only to find people who experience this problem quite a lot, mostly when using connection pooling will appear this way, short connection should be very difficult to have this problem. The cause of the problem:

MySQL Server default "wait_timeout" is 28,800 seconds or 8 hours, means that if a connection idle time exceed 8 hours, MySQL will automatically disconnect the connection, and connection pool is that the connection is still valid (because the school did not test the effectiveness of the connection), when the application when applying for the connection, it will lead to the above error.

1. In accordance with the error prompt, you can use the autoReconnect JDBC URL attribute, the actual test used autoReconnect = true & failOverReadOnly = false, but did not work, use the 5.1 version, you may really like the Internet before talking about only 4 version of the force.

2. No way, can only modify the parameters of the MySQL, wait_timeout a maximum of 31536000 that is 1 year, add in my.cnf:

[Mysqld]

wait_timeout = 31536000

interactive_timeout = 31536000

Restart effect, you need to modify these two parameters simultaneously.