mysql - 如何使用 c3p0 进行节点故障转移测试

Question

我们已经设置了具有三个节点的 MySQL NDB Cluster，这里是设置的详细信息。
Node1 - 多线程DataNode1，SQLNode1
Node2 - MultithreadedDataNode2, SQLNode2
Node3——管理节点

我们正在测试一些故障转移方案以确保设置有效。在客户端，我们使用 MySQLConnector v5.1.30 以及 c3p0 连接池。客户端配置了多主机参数。因此，如果其中一个节点或应用程序出现故障，JDBC 查询应该在另一个节点上执行并继续响应。

但是当 SQLNode(Port: 3306) 宕机时，我们正在观察异常行为。连接不会故障转移到另一个节点。

配置如下:

<bean id="myDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
                destroy-method="close">
        <property name="driverClass" value="com.mysql.jdbc.ReplicationDriver" />                            <!-- useConfigs=clusterBase -->
        <property name="jdbcUrl" value="jdbc:mysql:replication://192.168.102.22,192.168.102.23/hhmefep?autoReconnect=true&amp;failOverReadOnly=false&amp;roundRobinLoadBalance=true" /> 
        <property name="user" value="root"/>
        <property name="password" value="changeit"/>
        <property name="acquireIncrement" value="2" />
        <property name="minPoolSize" value="50" />
        <property name="maxPoolSize" value="100" />
        <property name="maxStatements" value="2000" />
        <property name="maxIdleTime" value="3600" />
        <property name="connectionTesterClassName" value="com.mysql.jdbc.integration.c3p0.MysqlConnectionTester" />
        <property name="testConnectionOnCheckin" value="true" />
        <property name="testConnectionOnCheckout" value="false" />
        <property name="idleConnectionTestPeriod" value="30" />
    </bean>

当我启动客户端时，这两个节点已启动并正在运行。之后，我从第一个节点 (192.168.102.22) 终止了 mysqld 进程，我得到了以下 stackTrace，

org.hibernate.exception.JDBCConnectionException: could not execute query
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:99)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.loader.Loader.doList(Loader.java:2536)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2276)
at org.hibernate.loader.Loader.list(Loader.java:2271)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1716)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347)
at com.mi.persistence.dao.cdr.BganActiveCallsDaoImpl.findBganActiveCallsBy_Imsi_Nsapi_Apn(BganActiveCallsDaoImpl.java:53)
at sun.reflect.GeneratedMethodAccessor283.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy23.findBganActiveCallsBy_Imsi_Nsapi_Apn(Unknown Source)
at com.mi.persistence.service.cdr.BganActiveCallsServiceImpl.findBganActiveCallsBy_Imsi_Nsapi_Apn(BganActiveCallsServiceImpl.java:22)
at sun.reflect.GeneratedMethodAccessor282.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy24.findBganActiveCallsBy_Imsi_Nsapi_Apn(Unknown Source)
at com.mi.persistence.service.callhandler.BganAccessRequestServiceImpl.getPreeptedCalls(BganAccessRequestServiceImpl.java:384)
at com.mi.taskobjects.externalsigobj.radiusobj.BGANAccessRequest.process(BGANAccessRequest.java:175)
at com.mi.entities.scheduler.SchWorkerThread.run(SchWorkerThread.java:165)
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet successfully received from the server was 19,578 milliseconds ago.  The last packet sent successfully to the server was 0 milliseconds ago.
at sun.reflect.GeneratedConstructorAccessor66.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:409)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1127)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3715)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3604)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4155)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2615)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2776)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2838)
at com.mysql.jdbc.LoadBalancedMySQLConnection.execSQL(LoadBalancedMySQLConnection.java:159)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2082)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2212)
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:1953)
at org.hibernate.loader.Loader.doQuery(Loader.java:802)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274)
at org.hibernate.loader.Loader.doList(Loader.java:2533)
... 42 more
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3161)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3615)
... 56 more
Apr 24, 2014 2:13:13 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@18138d9 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
Apr 24, 2014 2:13:13 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@18138d9 -- APPARENT DEADLOCK!!! Complete Status: 
Managed Threads: 3
Active Threads: 3
Active Tasks: 
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@2dbdcf (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@1088a28 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@1a67efd (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)
Pending Tasks: 
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@1db547d
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@87fa45
    com.mchange.v2.c3p0.stmt.GooGooStatementCache$1StatementCloseTask@13fcd69
    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1c6dc6d
    com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@b198d1
    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1a7ce01
    com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@1c5be25
    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1469706
    com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@1654503
    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@195f1b4
    com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@12f893d
    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1db4400
    com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@4d7ab3
    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@b29aa5
    com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@1c6fb4f
    com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@9d2c8e
    com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@d843e0
    com.mchange.v2.c3p0.stmt.GooGooStatementCache$1StmtAcquireTask@504b76
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@18a408c
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@193e4a4
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@87d60d
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@1f6002a
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@184e113
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@d4bbb0
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@6e4a4c
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@cfc9f4
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@1d3c0f3
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@120989c
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@1034f45
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@497a1b
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@1ef8e0b
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@568dc9
    com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask@76bb9c
Pool thread stack traces:
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
    java.lang.Thread.sleep(Native Method)
    com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2396)
    com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2326)
    com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:832)
    com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    sun.reflect.GeneratedConstructorAccessor27.newInstance(Unknown Source)
    sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:417)
    com.mysql.jdbc.LoadBalancingConnectionProxy.createConnectionForHost(LoadBalancingConnectionProxy.java:383)
    com.mysql.jdbc.RandomBalanceStrategy.pickConnection(RandomBalanceStrategy.java:75)
    com.mysql.jdbc.LoadBalancingConnectionProxy.pickNewConnection(LoadBalancingConnectionProxy.java:711)
    com.mysql.jdbc.LoadBalancingConnectionProxy.dealWithInvocationException(LoadBalancingConnectionProxy.java:415)
    com.mysql.jdbc.LoadBalancingConnectionProxy.invoke(LoadBalancingConnectionProxy.java:654)
    com.mysql.jdbc.LoadBalancingConnectionProxy.invoke(LoadBalancingConnectionProxy.java:549)
    $Proxy22.ping(Unknown Source)
    com.mysql.jdbc.ReplicationConnection.ping(ReplicationConnection.java:986)
    sun.reflect.GeneratedMethodAccessor13.invoke(Unknown Source)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    com.mchange.v2.c3p0.impl.NewProxyConnection.rawConnectionOperation(NewProxyConnection.java:1315)
    com.mysql.jdbc.integration.c3p0.MysqlConnectionTester.activeCheckConnection(MysqlConnectionTester.java:78)
    com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
    com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishResourceOnCheckin(C3P0PooledConnectionPool.java:301)
    com.mchange.v2.resourcepool.BasicResourcePool.attemptRefurbishResourceOnCheckin(BasicResourcePool.java:1606)
    com.mchange.v2.resourcepool.BasicResourcePool.access$200(BasicResourcePool.java:32)
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask.run(BasicResourcePool.java:1228)
    com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
    java.lang.Thread.sleep(Native Method)
    com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2396)
    com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2326)
    com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:832)
    com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    sun.reflect.GeneratedConstructorAccessor27.newInstance(Unknown Source)
    sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:417)
    com.mysql.jdbc.LoadBalancingConnectionProxy.createConnectionForHost(LoadBalancingConnectionProxy.java:383)
    com.mysql.jdbc.RandomBalanceStrategy.pickConnection(RandomBalanceStrategy.java:75)
    com.mysql.jdbc.LoadBalancingConnectionProxy.pickNewConnection(LoadBalancingConnectionProxy.java:711)
    com.mysql.jdbc.LoadBalancingConnectionProxy.dealWithInvocationException(LoadBalancingConnectionProxy.java:415)
    com.mysql.jdbc.LoadBalancingConnectionProxy.invoke(LoadBalancingConnectionProxy.java:654)
    com.mysql.jdbc.LoadBalancingConnectionProxy.invoke(LoadBalancingConnectionProxy.java:549)
    $Proxy22.ping(Unknown Source)
    com.mysql.jdbc.ReplicationConnection.ping(ReplicationConnection.java:986)
    sun.reflect.GeneratedMethodAccessor13.invoke(Unknown Source)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    com.mchange.v2.c3p0.impl.NewProxyConnection.rawConnectionOperation(NewProxyConnection.java:1315)
    com.mysql.jdbc.integration.c3p0.MysqlConnectionTester.activeCheckConnection(MysqlConnectionTester.java:78)
    com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
    com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishResourceOnCheckin(C3P0PooledConnectionPool.java:301)
    com.mchange.v2.resourcepool.BasicResourcePool.attemptRefurbishResourceOnCheckin(BasicResourcePool.java:1606)
    com.mchange.v2.resourcepool.BasicResourcePool.access$200(BasicResourcePool.java:32)
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask.run(BasicResourcePool.java:1228)
    com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
    java.lang.Thread.sleep(Native Method)
    com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2396)
    com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2326)
    com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:832)
    com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    sun.reflect.GeneratedConstructorAccessor27.newInstance(Unknown Source)
    sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:417)
    com.mysql.jdbc.LoadBalancingConnectionProxy.createConnectionForHost(LoadBalancingConnectionProxy.java:383)
    com.mysql.jdbc.RandomBalanceStrategy.pickConnection(RandomBalanceStrategy.java:75)
    com.mysql.jdbc.LoadBalancingConnectionProxy.pickNewConnection(LoadBalancingConnectionProxy.java:711)
    com.mysql.jdbc.LoadBalancingConnectionProxy.dealWithInvocationException(LoadBalancingConnectionProxy.java:415)
    com.mysql.jdbc.LoadBalancingConnectionProxy.invoke(LoadBalancingConnectionProxy.java:654)
    com.mysql.jdbc.LoadBalancingConnectionProxy.invoke(LoadBalancingConnectionProxy.java:549)
    $Proxy22.ping(Unknown Source)
    com.mysql.jdbc.ReplicationConnection.ping(ReplicationConnection.java:986)
    sun.reflect.GeneratedMethodAccessor13.invoke(Unknown Source)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    com.mchange.v2.c3p0.impl.NewProxyConnection.rawConnectionOperation(NewProxyConnection.java:1315)
    com.mysql.jdbc.integration.c3p0.MysqlConnectionTester.activeCheckConnection(MysqlConnectionTester.java:78)
    com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:368)
    com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishResourceOnCheckin(C3P0PooledConnectionPool.java:301)
    com.mchange.v2.resourcepool.BasicResourcePool.attemptRefurbishResourceOnCheckin(BasicResourcePool.java:1606)
    com.mchange.v2.resourcepool.BasicResourcePool.access$200(BasicResourcePool.java:32)
    com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask.run(BasicResourcePool.java:1228)
    com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

如有遗漏请指正..
谢谢，
基本

Answer 1

所以，发生的事情很清楚:c3p0 正在测试 checkin 时的连接。这些测试挂起，既没有成功也没有失败，最终导致线程池饱和和死锁。

我不能确定回答的问题是连接测试挂起的原因。从堆栈跟踪中可以清楚地看出，他们试图做的是重新连接，这是您想要发生的，但是要连接到您的复制(从)服务器。相反，重新连接失败，并且线程正在休眠。查看 mysql 的 ConnectionImpl 类的源代码，connectWithRetry 休眠 initialTimout 秒(默认 2)并重试 maxReconnects 时间(默认 3)。默认情况下，这意味着事情最多只能挂起 6 秒。不过，看起来您遇到的挂起时间可能比这更长。

一种解决方法是只设置 autoReconnect=false。然后连接测试可能会失败，c3p0 将尝试获取一个新的连接，这有望从故障转移服务器成功。

要尝试的其他事情是减少 initialTimeout 和 maxConnects 以加快失败速度。同样，如果内部重新连接失败，c3p0 将重新获取死连接，现在应该指向故障转移服务器。

最终，这里有几个未知数:(1) 您的复制服务器(您的 Connections 应该与之重新连接的那台服务器)是否正常运行？因为明显的问题是 mysql 驱动程序在失败时无法建立新的连接，真正的问题是为什么 com.mysql.jdbc.ReplicationDriver 没有像宣传的那样表现，而是连接到备用服务器。一种可能性是替代服务器存在问题。请确认您可以直接连接到 [jdbc:mysql://192.168.102.23/hhmefep]。如果没有，那是你的问题! (2) 如果可以连接到alt服务器，我们仍然不知道connectWithRetries(...)之前的故障转移逻辑是否真的在工作，也就是说，它是否在尝试连接到复制服务器？ (可能值得做的一件事是有意关闭复制的服务器，这样就没有什么可以进行故障转移了。应用程序是否更干净地失败了？)

我想，作为一个实际问题，我会验证复制服务器是否正常工作，减少 initialTimout and maxReconnects (也许是 1 和 1)，然后再试一次。如果这不起作用，我会将 autoReconnect 设置为 false。如果确实将 autoReconnect 设置为 false，则可以使用 c3p0 参数 maxConnectionAge 来确保，当主服务器恢复时，Connections 被(公平地)迅速替换为返回到 master 的 Connections。将 maxCoonnectionAge 设置为几分钟(而不是几秒钟，否则您将通过连接搅动并降低性能)。

祝你好运!