服务器上有几个定时任务在跑，每分钟执行一次的那种，于是服务器上每隔一小会就会从报出"discard connection"的异常。
异常信息：
discard connection
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet successfully received from the server was 60,003 milliseconds ago. The last packet sent successfully to the server was 6 milliseconds ago. at sun.reflect.GeneratedConstructorAccessor141.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at com.mysql.jdbc.Util.handleNewInstance(Util.java:425) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:990) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3562) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3462) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3905) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2530) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2683) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2495) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1903) at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1242) at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3051) at com.alibaba.druid.filter.FilterEventAdapter.preparedStatement_execute(FilterEventAdapter.java:440) at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3049) at com.alibaba.druid.wall.WallFilter.preparedStatement_execute(WallFilter.java:619) at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3049) at com.alibaba.druid.filter.FilterEventAdapter.preparedStatement_execute(FilterEventAdapter.java:440) at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3049) at com.alibaba.druid.proxy.jdbc.PreparedStatementProxyImpl.execute(PreparedStatementProxyImpl.java:167) at com.alibaba.druid.pool.DruidPooledPreparedStatement.execute(DruidPooledPreparedStatement.java:498) at sun.reflect.GeneratedMethodAccessor1981.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:59) at com.sun.proxy.$Proxy324.execute(Unknown Source) at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:63) at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79) at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63) at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:326) at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109) at com.github.pagehelper.PageInterceptor.intercept(PageInterceptor.java:143) at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:61) at com.sun.proxy.$Proxy317.query(Unknown Source) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141) at sun.reflect.GeneratedMethodAccessor167.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433) at com.sun.proxy.$Proxy161.selectList(Unknown Source) at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230) at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:139) at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:76) at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59) at com.sun.proxy.$Proxy179.getTaskList(Unknown Source) at cn.ce.marketingcenter.cron.global.AppGeneralInfoTask.updateGeneralStatus(AppGeneralInfoTask.java:79) at cn.ce.marketingcenter.cron.global.AppGeneralInfoTask$$FastClassBySpringCGLIB$$f43c3b81.invoke(<generated>) at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:746) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:88) at cn.ce.marketingcenter.config.aspect.cron.CronAspect.aspect(CronAspect.java:91) at sun.reflect.GeneratedMethodAccessor161.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:246) at org.springframework.cloud.context.scope.GenericScope$LockedScopedProxyFactoryBean.invoke(GenericScope.java:494) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688) at cn.ce.marketingcenter.config.aspect.cron.CronAspect$$EnhancerBySpringCGLIB$$e4f729ac.aspect(<generated>) at sun.reflect.GeneratedMethodAccessor161.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:644) at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:633) at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:70) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:88) at cn.ce.marketingcenter.config.aspect.cron.CronAspect.aspect(CronAspect.java:91) at sun.reflect.GeneratedMethodAccessor161.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:644) at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:633) at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:70) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688) at cn.ce.marketingcenter.cron.global.AppGeneralInfoTask$$EnhancerBySpringCGLIB$$e4eed146.updateGeneralStatus(<generated>) at sun.reflect.GeneratedMethodAccessor299.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.springframework.scheduling.support.ScheduledMethodRunnable.run(ScheduledMethodRunnable.java:84) at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54) at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:93) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) 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:3014) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3472) ... 90 common frames omitted
当时的druid配置：
druid: connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500 #池启动时创建的连接数量 initialSize: 5 #池中保持空闲的最少连接数 minIdle: 5 #最大连接数量 maxActive: 2000 #合并多个DruidDataSource的监控数据 useGlobalDataSourceStat: true #获取连接超时等待时间，20秒 maxWait: 20000 # 通过别名的方式配置扩展插件，多个英文逗号分隔，常用的插件有： # 监控统计用的filter:stat # 日志用的filter:slf4j # 防御sql注入的filter:wall filters: stat,wall,slf4j #开启池的prepared statement 功能，并且指定每个连接上PSCache的大小 poolPreparedStatements: true maxPoolPreparedStatementPerConnectionSize: 20 #连接保持空闲而不被驱逐的最长时间,250秒（比mysql设定的wait_timeout小一点，提前关闭） minEvictableIdleTimeMillis: 250000 #检查连接池中空闲连接的间隔,60秒 timeBetweenEvictionRunsMillis: 60000 #申请连接的时候检测，如果空闲时间大于timeBetweenEvictionRunsMillis，执行validationQuery检测连接是否有效 testWhileIdle: true #表示从连接池中获取连接前是否运行validationQuery，true=运行[默认]，false=不运行 testOnBorrow: false #表示将连接归还连接池前是否运行validationQuery，true=运行，false=不运行[默认] testOnReturn: false validationQuery: SELECT 1 FROM DUAL当时mysql的配置：
wait_timeout=300
解决办法：
把testOnBorrow改为true，异常信息不再出现
原因分析：
因为在连接池拿到连接要去工作的时候，发现连接已经失效。不要因为配置了 testWhileIdle + minEvictableIdleTimeMillis 就认为能把testOnBorrow设置为false，还是要在从连接池拿连接的时候先检测一下有效性。
