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c3p0配备解决java.net.SocketException: Broken pipe

日期：2014-05-16　 浏览次数：20466 次

c3p0配置解决java.net.SocketException: Broken pipe

最近的一个项目在Hibernate使用C3P0的连接池，数据库为Mysql。开发测试没有问题，在运行中每个一段长的空闲时间就出现异常Communications link failure due to underlying exception:

java 代码
  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的文档，以及Connector/J的文档以及在线说明发现，出现这种异常的原因是：

Mysql服务器默认的“wait_timeout”是8小时，也就是说一个connection空闲超过8个小时，Mysql将自动断开该connection。这就是问题的所在，在C3P0 pools中的connections如果空闲超过8小时，Mysql将其断开，而C3P0并不知道该connection已经失效，如果这时有Client请求connection，C3P0将该失效的Connection提供给Client，将会造成上面的异常。

解决的方法有3种：

  1. 增加wait_timeout的时间。
  2. 减少Connection pools中connection的lifetime。
  3. 测试Connection pools中connection的有效性。

当然最好的办法是同时综合使用上述3种方法，下面就DBCP和C3P0分别做一说明，假设wait_timeout为默认的8小时

DBCP增加以下配置信息:

  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增加以下配置信息:

  1. //获取connnection时测试是否有效
  2. testConnectionOnCheckin = true
  3. //自动测试的table名称
  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

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