C3P0 配置

官方文檔 : http://www.mchange.com/projects/c3p0/index.html

3

30

1000

false

Test

false

100

null

false

60

3

60

15

100

3

root

password

select id from test where id=1

300

false

true

root

false

con_test

30000

30

10

30

25

10

0

200

300

轉：http://www.wujianrong.com/archives/2007/08/c3p0.html

解決MYSQL 8小時問題

最近的一個項目在Hibernate使用C3P0的鏈接池，數據庫爲Mysql。開發測試沒有問題，在運行中每一個一段長的空閒時間就出現異常:

java 代碼

 

1. org.hibernate.exception.JDBCConnectionException: could not execute query
2. at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74)
3. at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
4. .......
5. Caused by: com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed due to underlying exception/error:
6. ** BEGIN NESTED EXCEPTION **
7. com.mysql.jdbc.CommunicationsException
8. MESSAGE: Communications link failure due to underlying exception:
9. ** BEGIN NESTED EXCEPTION **
10. java.net.SocketException
11. MESSAGE: Broken pipe
12. STACKTRACE:
13. java.net.SocketException: Broken pipe
14. at java.net.SocketOutputStream.socketWrite0(Native Method)
15. ......
16. ** END NESTED EXCEPTION **

 

查看了Mysql的文檔，以及Connector/J的文檔以及在線說明發現，出現這種異常的緣由是：

Mysql服務器默認的「wait_timeout」是8小時，也就是說一個connection空閒超過8個小時，Mysql將自動斷開該 connection。這就是問題的所在，在C3P0 pools中的connections若是空閒超過8小時，Mysql將其斷開，而C3P0並不知道該connection已經失效，若是這時有 Client請求connection，C3P0將該失效的Connection提供給Client，將會形成上面的異常。

解決的方法有3種：

1. 增長wait_timeout的時間。
2. 減小Connection pools中connection的lifetime。
3. 測試Connection pools中connection的有效性。

 

固然最好的辦法是同時綜合使用上述3種方法，下面就DBCP和C3P0分別作一說明，假設wait_timeout爲默認的8小時

DBCP增長如下配置信息:

 

1. //set to 'SELECT 1'
2. validationQuery = "SELECT 1"
3. //set to 'true'
4. testWhileIdle = "true"
5. //some positive integer
6. timeBetweenEvictionRunsMillis = 3600000
7. //set to something smaller than 'wait_timeout'
8. minEvictableIdleTimeMillis = 18000000
9. //if you don't mind a hit for every getConnection(), set to "true"
10. testOnBorrow = "true"

 

C3P0增長如下配置信息:

 

1. //獲取connnection時測試是否有效
2. testConnectionOnCheckin = true
3. //自動測試的table名稱

    

    

4. automaticTestTable=C3P0TestTable

    

    

5. //set to something much less than wait_timeout, prevents connections from going stale
6. idleConnectionTestPeriod = 18000
7. //set to something slightly less than wait_timeout, preventing 'stale' connections from being handed out
8. maxIdleTime = 25000
9. //if you can take the performance 'hit', set to "true"
10. testConnectionOnCheckout = true

 

更多的配置信息你們能夠查看C3P0文檔，Connector/J文檔，以及DBCP的文檔。

轉: http://www.javaeye.com/article/38506

我本身的配置:

jdbc.driverClass=com.mysql.jdbc.Driver

jdbc.jdbcUrl = jdbc:mysql://localhost:3306/test

jdbc.user = root

jdbc.password = 12345

jdbc.miniPoolSize = 1

jdbc.maxPoolSize = 20

jdbc.initialPoolSize = 1

jdbc.maxIdleTime = 25000

jdbc.acquireIncrement = 1

jdbc.acquireRetryAttempts = 30

jdbc.acquireRetryDelay = 1000

jdbc.testConnectionOnCheckin = true

jdbc.automaticTestTable = c3p0TestTable

jdbc.idleConnectionTestPeriod = 18000

jdbc.checkoutTimeout=3000