通信鏈接失敗：使用C3P0重置連接

Question

我知道這已被問了很多次，但我堅持了它。

我驗證了以下幾件事：

IP address or hostname in JDBC URL is correct. 

Hostname in JDBC URL is also recognized by local DNS server. 

Port number is correct in JDBC URL. 

DB server is up. 

由於相同的DB調用工作有時，我相信它與相關「走出聯繫」。我們在發行時只有50-60 connections給DB。

不過，我相信C3PO connections可能已經用盡了。

我們有以下C3P0配置

<props> 
<prop key="hibernate.c3p0.timeout"> 
44000 
<!-- seconds --> 
</prop> 
<prop key="hibernate.c3p0.min_size">5</prop> 
<prop key="hibernate.c3p0.max_size">5</prop> 
<prop key="hibernate.c3p0.initial_pool_size">5</prop> 
<prop key="hibernate.c3p0.idle_test_period"> 
60 
<!-- seconds --> 
</prop> 
<prop key="hibernate.c3p0.acquire_increment">2</prop> 
<prop key="hibernate.c3p0.max_statements">50</prop> 
<prop key="hibernate.c3p0.preferredTestQuery">SELECT 1 FROM DUAL</prop> 
<prop key="hibernate.show_sql">true</prop> 
</props> 

大多數條目在這裏沒有定義，默認情況下被使用。讓我知道這是否是問題，理由會非常有幫助。

Maximum number C3P0 connections by default are 15但是我們幾乎總是越過這個限制，並且不會遇到這個問題（同樣可能是C3P0的acquireIncrement屬性在這種情況下支持連接）。

堆棧跟蹤：

org.springframework.dao.DataAccessResourceFailureException: could not execute query; nested exception is org.hibernate.exception.JDBCConnectionException: could not execute query 
at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:625) 
at org.springframework.orm.hibernate3.AbstractSessionFactoryBean.convertHibernateAccessException(AbstractSessionFactoryBean.java:303) 
at org.springframework.orm.hibernate3.AbstractSessionFactoryBean.translateExceptionIfPossible(AbstractSessionFactoryBean.java:282) 
at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:58) 
at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213) 
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:163) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) 
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) 
at $Proxy34.findByName(Unknown Source) 
at a.b.c.d.e.f(A.java:941) 
at a.b.c.d.e.f$$FastClassByCGLIB$$a171eb15.invoke(<generated>) 
at org.springframework.internal.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149) 
at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:688) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150) 
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) 
at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:621) 
at com.amazon.mobiusdatabase.activity.IMBatchActivity$$EnhancerByCGLIB$$42d90986.getLatestBatchByStatus(<generated>) 
at com.amazon.coral.reflect.$2198.invoke(Unknown Source) 
at com.amazon.coral.service.DefaultActivityInvoker.invoke(DefaultActivityInvoker.java:40) 
at com.amazon.coral.service.ContinuationActivityInvokerFactory$1.invoke(ContinuationActivityInvokerFactory.java:92) 
at com.amazon.coral.service.ActivityHandler.invoke(ActivityHandler.java:269) 
at com.amazon.coral.service.ActivityHandler.before(ActivityHandler.java:157) 
at com.amazon.coral.service.TransmutingContinuationHandler.before(TransmutingContinuationHandler.java:51) 
at com.amazon.coral.service.Chain.componenteBefore(Chain.java:98) 
at com.amazon.coral.service.Chain.before(Chain.java:76) 
at com.amazon.coral.service.helper.ChainHelper.before(ChainHelper.java:103) 
at com.amazon.coral.service.AbstractOrchestrator.doWork(AbstractOrchestrator.java:60) 
at com.amazon.coral.service.PassiveOrchestrator.enqueue(PassiveOrchestrator.java:68) 
at com.amazon.coral.service.GracefulShutdownOrchestrator.enqueue(GracefulShutdownOrchestrator.java:79) 
at com.amazon.coral.service.helper.OrchestratorHelper.enqueue(OrchestratorHelper.java:44) 
at com.amazon.coral.service.batch.BatchProtocolOrchestrator.enqueue(BatchProtocolOrchestrator.java:97) 
at com.amazon.coral.service.bobcat.BobcatEndpoint.invoke(BobcatEndpoint.java:194) 
at org.apache.catalina.valves.SSLValve.invoke(SSLValve.java:113) 
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) 
at org.apache.coyote.http11.Http11NioProcessor.process(Http11NioProcessor.java:894) 
at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:719) 
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:2101) 
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) 
at java.lang.Thread.run(Thread.java:662) 
Caused by: org.hibernate.exception.JDBCConnectionException: could not execute query 
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:97) 
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) 
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure 

Last packet sent to the server was 1 ms ago. 
at sun.reflect.GeneratedConstructorAccessor143.newInstance(Unknown Source) 
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) 
at java.lang.reflect.Constructor.newInstance(Constructor.java:513) 
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) 
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074) 
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2985) 
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2871) 
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3414) 
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936) 
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060) 
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2542) 
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1734) 
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1885) 
at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:76) 
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208) 
at org.hibernate.loader.Loader.getResultSet(Loader.java:1808) 
at org.hibernate.loader.Loader.doQuery(Loader.java:697) 
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259) 
at org.hibernate.loader.Loader.doList(Loader.java:2228) 
... 49 more 
Caused by: java.net.SocketException: Connection reset 
at java.net.SocketInputStream.read(SocketInputStream.java:168) 
at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113) 
at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160) 
at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188) 
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2428) 

我們正在這一點的同時開火DB選擇查詢。

Answer 1

也許連接沒有正確關閉，所以你可以嘗試大幅度減少超時，看看你是否有同樣的問題。

<prop key="hibernate.c3p0.timeout">3000</prop> 

同時，你可以使用JMX探查像VisualVM監視C3P0連接，並直接看到在數據庫服務器上是否有「丟失」的連接。