我有一个正在生产中的 Grails 应用程序。今天早上我收到警报，发现服务器无法解析。雄猫不停地旋转。我研究了一下，看起来这与 MySQL 导致连接在 8 小时不活动后超时有关。我在 stackoverflow 上找到了例子有类似问题的人。然而，所有这些人都提到，如果他们再次访问服务器并且连接被刷新。对我来说，该网站完全瘫痪了，Tomcat 也没有响应。听起来是不是还有其他事情在起作用？
Tomcat 日志中的最后一个异常
2011-Aug-30 23:58:43,283 [TP-Processor19] org.hibernate.util.JDBCExceptionReporter
ERROR The last packet successfully received from the server was 37,118,147 milliseconds ago. The last packet sent successfully to the server was 37,122,138 milliseconds ago. \
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.
2011-Aug-30 23:58:43,290 [TP-Processor19] org.codehaus.groovy.grails.web.errors.GrailsExceptionResolver
ERROR Exception occurred when processing request: [GET] /picks/ncaafb
Stacktrace follows:
java.net.SocketException: Connection timed out
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:123)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3302)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1940)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2113)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2568)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2113)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2275)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2275)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:96)
at sportsdb.Season.getCurrentNCAAFootballSeason(Season.groovy:93)
at PicksController$_closure2.doCall(PicksController.groovy:60)
at PicksController$_closure2.doCall(PicksController.groovy)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:774)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:703)
at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:896)
at java.lang.Thread.run(Thread.java:662)
2011-Aug-30 23:58:43,315 [TP-Processor19] org.hibernate.util.JDBCExceptionReporter
ERROR Already closed.
2011-Aug-30 23:58:43,315 [TP-Processor19] org.hibernate.util.JDBCExceptionReporter
ERROR Already closed.
2011-Aug-30 23:58:43,316 [TP-Processor19] org.codehaus.groovy.grails.web.servlet.GrailsDispatcherServlet
ERROR HandlerInterceptor.afterCompletion threw exception
org.hibernate.exception.GenericJDBCException: Cannot release connection
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:774)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:703)
at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:896)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.sql.SQLException: Already closed.
at org.apache.commons.dbcp.PoolableConnection.close(PoolableConnection.java:114)
at org.apache.commons.dbcp.PoolingDataSource$PoolGuardConnectionWrapper.close(PoolingDataSource.java:191)
at $Proxy7.close(Unknown Source)
... 6 more
我的计划是实施上面链接中提到的解决方案，但我想确保没有其他明显可疑的情况发生，因为我们得到了一些不同的结果（他们的连接是刷新的，而我的不是）。
如果您使用的是 Tomcat JNDI 数据源查看一些可以设置的参数在数据源上，例如 testOnBorrow。如果验证失败，连接将从池中删除。测试连接会产生一些性能开销，但它应该可以解决这样的问题。如果您将 minIdle/maxIdle 设置得较高，这可以解释为什么您在重新连接为其他人修复问题时仍然遇到问题。
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