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偶尔使用Amazon RDS MySQL和Play Framework 1.2.5挂起连接(c3p0默认设置)

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我们遇到了Amazon-hosted Play application with RDS Mysql的问题.

有时应用程序最终没有响应.今天我用jstack -F检查了线程状态,并且在c3p0连接的本机代码中存在多个线程：

Thread 14060: (state = IN_NATIVE)
 - java.net.SocketInputStream.socketRead0(java.io.FileDescriptor, byte[], int, int, int) @bci=0 (Compiled frame; information may be imprecise)
 - java.net.SocketInputStream.read(byte[], int, int, int) @bci=79, line=150 (Compiled frame)
 - java.net.SocketInputStream.read(byte[], int, int) @bci=11, line=121 (Compiled frame)
 - com.mysql.jdbc.util.ReadAheadInputStream.fill(int) @bci=262, line=114 (Compiled frame)
 - com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(byte[], int, int) @bci=176, line=161 (Compiled frame)
 - com.mysql.jdbc.util.ReadAheadInputStream.read(byte[], int, int) @bci=48, line=189 (Compiled frame)
 - com.mysql.jdbc.MysqlIO.readFully(java.io.InputStream, byte[], int, int) @bci=34, line=3036 (Compiled frame)
 - com.mysql.jdbc.MysqlIO.reuseAndReadPacket(com.mysql.jdbc.Buffer, int) @bci=23, line=3489 (Compiled frame)
 - com.mysql.jdbc.MysqlIO.reuseAndReadPacket(com.mysql.jdbc.Buffer) @bci=3, line=3478 (Compiled frame)
 - com.mysql.jdbc.MysqlIO.checkErrorPacket(int) @bci=12, line=4019 (Compiled frame)
 - com.mysql.jdbc.MysqlIO.sendCommand(int, java.lang.String, com.mysql.jdbc.Buffer, boolean, java.lang.String, int) @bci=428, line=2490 (Compiled frame)
 - com.mysql.jdbc.MysqlIO.sqlQueryDirect(com.mysql.jdbc.StatementImpl, java.lang.String, java.lang.String, com.mysql.jdbc.Buffer, int, int, int, boolean, java.lang.String, com.mysql.jdbc.Field[]) @bci=559, line=2651 (Compiled frame)
 - com.mysql.jdbc.ConnectionImpl.execSQL(com.mysql.jdbc.StatementImpl, java.lang.String, int, com.mysql.jdbc.Buffer, int, int, boolean, java.lang.String, com.mysql.jdbc.Field[], boolean) @bci=130, line=2677 (Compiled frame)
 - com.mysql.jdbc.ConnectionImpl.execSQL(com.mysql.jdbc.StatementImpl, java.lang.String, int, com.mysql.jdbc.Buffer, int, int, boolean, java.lang.String, com.mysql.jdbc.Field[]) @bci=17, line=2627 (Compiled frame)
 - com.mysql.jdbc.StatementImpl.executeQuery(java.lang.String) @bci=534, line=1556 (Compiled frame)
 - com.mysql.jdbc.DatabaseMetaData$9.forEach(java.lang.Object) @bci=174, line=5013 (Compiled frame)
 - com.mysql.jdbc.IterateBlock.doForAll() @bci=25, line=51 (Compiled frame)
 - com.mysql.jdbc.DatabaseMetaData.getTables(java.lang.String, java.lang.String, java.lang.String, java.lang.String[]) @bci=280, line=4991 (Compiled frame)
 - com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnectionNoQuery(java.sql.Connection, java.lang.Throwable[]) @bci=21, line=185 (Compiled frame)
 - com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnection(java.sql.Connection, java.lang.String, java.lang.Throwable[]) @bci=7, line=62 (Compiled frame)
 - com.mchange.v2.c3p0.AbstractConnectionTester.activeCheckConnection(java.sql.Connection) @bci=4, line=67 (Compiled frame)
 - com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(java.lang.Object) @bci=122, line=368 (Compiled frame)
 - com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishIdleResource(java.lang.Object) @bci=26, line=310 (Compiled frame)
 - com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask.run() @bci=35, line=1999 (Interpreted frame)
 - com.mchange.v2.async.ThreadPerTaskAsynchronousRunner$TaskThread.run() @bci=41, line=255 (Interpreted frame)

如果没有设置其他连接测试,则DefaultConnectionTester.activeCheckConnectionNoQuery似乎检查DatabaseMetaData.getTables.

C3p0手册有configuring proper connection testing和this answer的说明,有关于播放的c3p0设置的说明！但我想知道：

>有没有办法检查这个问题是什么？

>标准的“8小时后被杀死的Mysql连接”我在结果之前遇到过例外

>由于这样做,似乎有一些与c3p0 / Play / Hibernate的默认连接测试？

>我有预感,默认情况下c3p0不进行连接测试

>默认值idleConnectionTestPeriod = 0,testConnectionOnCheckin = false,testConnectionOnCheckout = false

>有没有办法为连接测试查询设置超时？

>即使我配置了一些明智的preferredTestQuery,例如,该查询是否也会挂起当前的getTables()调用？

>我还应该考虑其他什么吗？

使用automaticTestTable进行更新(不是解决方案)

我们设置c3p0.automaticTestTable以进行更合理的连接测试,但这似乎没有解决问题,只是改变了线程的堆栈跟踪.

在类似的情况下,我们现在有如下的线程堆栈：

"Task-Thread-for-com.mchange.v2.async.ThreadPerTaskAsynchronousRunner@6064cd08" daemon prio=10 tid=0x00007f53d403a000 nid=0x63dd runnable [0x00007f53dce4a000]
   java.lang.Thread.State: RUNNABLE
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:150)
        at java.net.SocketInputStream.read(SocketInputStream.java:121)
        at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114)
        at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161)
        at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189)
        - locked <0x00000000dbecd0d8> (a com.mysql.jdbc.util.ReadAheadInputStream)
        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3036)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3489)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3478)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4019)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2490)
        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2651)
        at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2677)
        - locked <0x00000000dbec1a70> (a com.mysql.jdbc.JDBC4Connection)
        at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2627)
        at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1556)
        - locked <0x00000000dbec1a70> (a com.mysql.jdbc.JDBC4Connection)
        - locked <0x00000000d1330078> (a com.mysql.jdbc.StatementImpl)
        at com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnection(DefaultConnectionTester.java:73)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:374)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishIdleResource(C3P0PooledConnectionPool.java:310)
        at com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask.run(BasicResourcePool.java:1999)
        at com.mchange.v2.async.ThreadPerTaskAsynchronousRunner$TaskThread.run(ThreadPerTaskAsynchronousRunner.java:255)

Play线程正在等待获取数据库连接：

"play-thread-3" prio=10 tid=0x00007f53c400b000 nid=0x5b3e in Object.wait() [0x00007f53ddd57000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x00000000db9f38f8> (a com.mchange.v2.resourcepool.BasicResourcePool)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:579)
        - locked <0x00000000db9f38f8> (a com.mchange.v2.resourcepool.BasicResourcePool)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:584)
        ... (n?it? vaihtelevat m??r?t)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:584)
        - locked <0x00000000db9f38f8> (a com.mchange.v2.resourcepool.BasicResourcePool)
        at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:584)
        - locked <0x00000000db9f38f8> (a com.mchange.v2.resourcepool.BasicResourcePool)
        at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
        at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
        at org.hibernate.ejb.connection.InjectedDataSourceConnectionProvider.getConnection(InjectedDataSourceConnectionProvider.java:71)
        at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
        at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)
        at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:160)
        at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:81)
        at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1473)
        at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:60)
        at play.db.jpa.JPAPlugin.startTx(JPAPlugin.java:377)
        at play.db.jpa.JPAPlugin.beforeInvocation(JPAPlugin.java:345)
        at play.plugins.PluginCollection.beforeInvocation(PluginCollection.java:473)
        at play.Invoker$Invocation.before(Invoker.java:217)
        at play.Invoker$Invocation.run(Invoker.java:277)
        at play.server.PlayHandler$NettyInvocation.run(PlayHandler.java:229)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
        at java.util.concurrent.FutureTask.run(FutureTask.java:166)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:178)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:292)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
        at java.lang.Thread.run(Thread.java:722)

一些说明：

>有可能(至少在理论上),即使我发现这种情况不太可能,许多连接恰好在堆栈转储被重复的同时进行测试.
>在another question,有人提到数据死锁或硬件/网络问题可能会导致这种行为.

>至少不应该有任何正在进行的架构修改.

br,Touko

回答自己：

>找不到连接挂起的原因:(

> RDS有MySQL的error.log,遗憾的是没有

> Play有一些c3p0 ComboPooledDataSource的默认设置(在DBPlugin.onApplicationStart()中)

> idleTimeExcessConnections：来自application.conf db.pool.maxIdleTimeExcessConnections(默认为0)
> checkoutTimeout：来自application.conf db.pool.timeout(默认5000)
> idleConnectionTestPeriod：10
> setTestConnectionOnCheckin：true
>此外,conf / c3p0.properties可用于设置自定义属性

>还没有找到设置连接测试超时的方法(可能不支持简短的DefaultConnectionTester源代码查找)

我们将继续设置c3p0.automaticTestTable并检查以后是否会出现任何问题.

更新：不幸的是我们还没有摆脱问题:(还有自动测试,连接测试似乎已经卡住java.net.SocketInputStream.socketRead0(本机方法)

再次回答自己：

我们最终尝试使用c3p0：s maxAdministrativeTaskTime尝试这种“连接测试查询的设置超时”方法.这有点像黑客,所以要看看这是否可以作为最终解决方案(如果可行).

到目前为止还没有问题,我们将看到它是如何工作的.日志中也没有c3p0错误/堆栈跟踪,我希望这些中断能够显示在日志中吗？还没有发生超时,或者我们应该调整日志配置以显示c3p0日志.

更新(2013-04-04)：在此之后,问题(可能)并没有经常发生,但偶尔会发生:(

解决方法:

再次回答自己：

我们首先使用为MySQL驱动程序指定的socketTimeout,以便连接测试不会卡住.

似乎底层TCP连接结束,以便服务器没有应答(TCP ACK或任何东西).

更新：最终的解决方案是通过为AWS支持提供tcpdump,他们在AWS基础架构中找到了一些案例.他们建议我们在EC2实例的安全组中打开短暂的端口范围.在AWS forum进行更多讨论.

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