Mysql 检查JDBC连接是否可写；使用preferredTestQuery或ConnectionTester
当前设置： 服务主机（Java）连接到（JDBC）主数据库（MySQL），并有一个从数据库（只读）以确保可靠性 场景： 在翻转的情况下，我需要升级从到新的主。当前母版变为只读，新母版升级为读写。我希望使用测试查询（执行对数据库的可写查询）自动将C3P0连接池刷新到新主机 创意： 探索一种自动刷新JDBC连接池的方法，以便在出现翻转时连接到新主机（当前主机将是RO，从机将升级为RW，主机cname将更新） 当前配置Mysql 检查JDBC连接是否可写；使用preferredTestQuery或ConnectionTester,mysql,jdbc,c3p0,Mysql,Jdbc,C3p0,当前设置： 服务主机（Java）连接到（JDBC）主数据库（MySQL），并有一个从数据库（只读）以确保可靠性 场景： 在翻转的情况下，我需要升级从到新的主。当前母版变为只读，新母版升级为读写。我希望使用测试查询（执行对数据库的可写查询）自动将C3P0连接池刷新到新主机 创意： 探索一种自动刷新JDBC连接池的方法，以便在出现翻转时连接到新主机（当前主机将是RO，从机将升级为RW，主机cname将更新） 当前配置 <property name="driverCla
<property name="driverClass" value="${DriverClass}" />
<property name="jdbcUrl" value="${ReadWriteDatabaseURL}${AccountDatabaseName}${JDBCProperties}" />
<property name="user" value="${ReadWriteDatabaseCredentials}.principal" />
<property name="password" value="${ReadWriteDatabaseCredentials}.credential" />
<property name="testConnectionOnCheckout" value="true"/>
<property name="testConnectionOnCheckin" value="false" />
<property name="preferredTestQuery" value="update existing_table set value = now() where id = 1;"/>
<property name="maxIdleTime" value="44000"/>
<property name="idleConnectionTestPeriod" value="30"/>
<property name="maxStatements" value="50"/>
<property name="minPoolSize" value="3"/>
<property name="maxPoolSize" value="3"/>
<property name="acquireIncrement" value="2"/>
<property name="checkoutTimeout" value="15000"/>
<property name="acquireRetryDelay" value="1000"/>
谢谢我不能对更大的故障切换问题发表评论，但是您当然可以定义一个基本上可以做任何事情的
connectiontestc3p0语句。executeQuery（…）INSERTConnectionTesterpreferredTestQueryrootCauseOutParamHoldernull如果希望忽略
preferredTestQuerypreferredTestQuery异常）。是的，这正是问题所在。感谢你的帮助，史蒂夫，谢谢。我指的是你的过度堆积。并设置com.mchange.v2.resourcepool.BasicResourcePool
的日志级别进行调试，发现java.sql.SQLException:无法使用executeQuery（）发出数据操作语句。
但是，我想知道它是如何使用testConnectionOnCheckin
的，而不是testConnectionOnCheckout
当使用testConnectionOnCheckin=true时，我能够切换到master并且没有问题。但是，如果使用testConnectionOnCheckin
，则不会更新表值。我想知道testConnectionOnCheckin
是否使用executeUpdate（）？或者，如果忽略错误，则不确定如何将数据连接重置为新主机。无论是签入还是签出，测试都是相同的。但是，签入失败，虽然您应该能够将其写入日志，但在应用程序行为方面却不太明显。如果您使用executeQuery
拒绝的“查询”，则在签出时测试时，您将始终无法获得连接。签入测试是异步的。您的应用程序不会出现问题，但在幕后，c3p0将始终销毁和重新获取，而不是重用签入连接（看起来已断开）。在故障切换方面，这似乎很好，因为重新获取可能总是来自最新的主控器。但就性能而言，它不会很好。它仍然比简单的连接获取要好，因为c3p0将异步批获取。但是你将通过连接进行转换，无论需要多少开销。
Caused by: org.hibernate.exception.GenericJDBCException: Could not open connection
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:221) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:157) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.internal.SessionImpl.connection(SessionImpl.java:550) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.springframework.orm.hibernate4.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:450) ~[spring-orm-4.3.20.RELEASE.jar:4.3.20.RELEASE]
... 42 more
Caused by: java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:118) ~[mchange-commons-java-0.2.10.jar:0.2.10]
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:77) ~[mchange-commons-java-0.2.10.jar:0.2.10]
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:690) ~[c3p0-0.9.5.1.jar:0.9.5.1]
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:140) ~[c3p0-0.9.5.1.jar:0.9.5.1]
at org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource.getConnection(AbstractRoutingDataSource.java:164) ~[spring-jdbc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.hibernate.service.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:141) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:292) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:214) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:157) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.internal.SessionImpl.connection(SessionImpl.java:550) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.springframework.orm.hibernate4.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:450) ~[spring-orm-4.3.20.RELEASE.jar:4.3.20.RELEASE]
... 42 more
Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@4c86da0c -- timeout at awaitAvailable()
at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1467) ~[c3p0-0.9.5.1.jar:0.9.5.1]
at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:644) ~[c3p0-0.9.5.1.jar:0.9.5.1]
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:554) ~[c3p0-0.9.5.1.jar:0.9.5.1]
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutAndMarkConnectionInUse(C3P0PooledConnectionPool.java:758) ~[c3p0-0.9.5.1.jar:0.9.5.1]
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:685) ~[c3p0-0.9.5.1.jar:0.9.5.1]
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:140) ~[c3p0-0.9.5.1.jar:0.9.5.1]
at org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource.getConnection(AbstractRoutingDataSource.java:164) ~[spring-jdbc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
at org.hibernate.service.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:141) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:292) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:214) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:157) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.hibernate.internal.SessionImpl.connection(SessionImpl.java:550) ~[hibernate-core-4.2.2.Final.jar:4.2.2.Final]
at org.springframework.orm.hibernate4.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:450) ~[spring-orm-4.3.20.RELEASE.jar:4.3.20.RELEASE]
... 42 more