【发布时间】：2012-11-16 21:28:31
【问题描述】：
我知道这个问题已经被问过很多次了，但我一直坚持。
我验证了以下几点：
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.
由于有时相同的数据库调用有效，我相信它与“失去连接”有关。在发布时，我们只有50-60 connections 给 DB。
不过，我相信C3PO connections 可能已经筋疲力尽了。
我们有以下 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>
这里没有定义大部分条目，使用默认值。让我知道这是否可能是问题和原因会非常有帮助。
Maximum number C3P0 connections by default are 15 但我们几乎一直越过这个限制并且不会遇到这个问题（在这种情况下支持连接可能是 C3P0 的 acquireIncrement 属性的 bcoz）。
堆栈跟踪：
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)
我们在 DB 上触发选择查询时得到了这个。
【问题讨论】：
-
嗨。不清楚你在问什么/问题是什么。您是否看到诸如“通信链接故障：连接重置”之类的异常，或者您是否面临池耗尽，即尝试签出连接冻结，无限期地等待未出现的连接？如果您看到异常，最好提供堆栈跟踪并提供一些有关异常发生情况的信息。
-
还要注意，在这个配置中，c3p0 池管理的连接不应该是 15 个，而是固定数量只有 5 个。如果您看到 15 个，您可能正在初始化 3 个池（不同的c3p0 数据源，或一个数据源与三种不同的身份验证凭据一起使用。
-
我们收到“通信链接故障：连接重置”。更新了问题。
-
嗨，这看起来像是一个杂项的死连接......你正在做一些连接测试，空闲连接，但你的测试制度是不完整的。我首先将 testConnectionOnCheckout 设置为 true，然后看看是否能解决问题。这是连接测试最可靠的方案，但它确实有性能成本。 （但是，您的 preferredTestQuery 会减少这种情况。）如果可行，一种高性能的方法会将 testConnectionOnCheckin 设置为 true 并测试空闲连接（就像您目前所做的那样）。见mchange.com/projects/c3p0/#configuring_connection_testing
标签： java mysql spring hibernate c3p0