我知道这已经被问过很多次了，但我一直坚持。
我验证了以下内容：
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。在问题发生时，我们只50-60 connections需要 DB。
不过，我相信这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>
大多数条目在此处未定义，使用默认值。让我知道这是否可能是问题和原因将非常有帮助。
Maximum number C3P0 connections by default are 15但是我们几乎一直越过这个限制并且不会遇到这个问题（acquireIncrement在这种情况下支持连接可能是C3P0的属性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)
我们在数据库上触发选择查询时得到了这个。