通过在SpringBoot中配置连接池属性解决MySql连接池Communications link failure问题

1.错误日志

2018-10-11 04:00:15,642 ERROR traceId:0 com.alibaba.druid.pool.DruidDataSource:1600 - discard connection   -- Exception: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure 
  
 The last packet successfully received from the server was 7,214,506 milliseconds ago.  The last packet sent successfully to the server was 7,214,451 milliseconds ago. 
 	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
 	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) 
 	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) 
 	at java.lang.reflect.Constructor.newInstance(Unknown Source) 
 	at com.mysql.jdbc.Util.handleNewInstance(Util.java:404) 
 	at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:988) 
 	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3552) 
 	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3452) 
 	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3893) 
 	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2526) 
 	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2673) 
 	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2549) 
 	at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1861) 
 	at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1192) 
 	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.proxy.jdbc.PreparedStatementProxyImpl.execute(PreparedStatementProxyImpl.java:167) 
 	at com.alibaba.druid.pool.DruidPooledPreparedStatement.execute(DruidPooledPreparedStatement.java:498) 
 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
 	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
 	at java.lang.reflect.Method.invoke(Unknown Source) 
 	at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:59) 
 	at com.sun.proxy.$Proxy171.execute(Unknown Source) 
 	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:63) 
 	at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79) 
 	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63) 
 	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324) 
 	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) 
 	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109) 
 	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83) 
 	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148) 
 	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141) 
 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
 	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
 	at java.lang.reflect.Method.invoke(Unknown Source) 
 	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433) 
 	at com.sun.proxy.$Proxy123.selectList(Unknown Source) 
 	at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230) 
 	at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:137) 
 	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:75) 
 	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59) 
 	at com.sun.proxy.$Proxy124.getNoviceMediaId(Unknown Source) 
 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
 	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
 	at java.lang.reflect.Method.invoke(Unknown Source) 
 	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333) 
 	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) 
 	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) 
 	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136) 
 	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) 
 	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213) 
 	at com.sun.proxy.$Proxy126.getNoviceMediaId(Unknown Source) 
 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
 	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
 	at java.lang.reflect.Method.invoke(Unknown Source) 
 	at org.springframework.scheduling.support.ScheduledMethodRunnable.run(ScheduledMethodRunnable.java:65) 
 	at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54) 
 	at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:81) 
 	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) 
 	at java.util.concurrent.FutureTask.run(Unknown Source) 
 	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown Source) 
 	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) 
 	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
 	at java.lang.Thread.run(Unknown Source) 
 Caused by: java.net.SocketException: Connection reset 
 	at java.net.SocketInputStream.read(Unknown Source) 
 	at java.net.SocketInputStream.read(Unknown Source) 
 	at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:101) 
 	at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:144) 
 	at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:174) 
 	at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3001) 
 	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3462) 
 	... 66 more

2.错误分析

在MySql中查询

mysql> show variables like 'wait_timeout';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wait_timeout  | 28800 |
+---------------+-------+
1 row in set (0.02 sec)

• 从查询结果，可知一个连接(Connection)的等待时间是28800秒，即8小时。
• 如果某个连接空闲超过8小时，则会断开该连接。
• MySql连接池默认情况下并不对连接的有效性进行校验。
• 如果程序使用一个已经断开的连接进行查询，则会报错如上所示。

3.纠错方法

3.1.说明

解决此类问题有很多种方式，其本质是增加有效性校验。

本文只叙述在SpringBoot通过Druid的解决方式，其他方式请参考解决。

3.2.添加依赖

        
        <dependency>
            <groupId>com.alibabagroupId>
            <artifactId>druid-spring-boot-starterartifactId>
            <version>1.1.9version>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-jdbcartifactId>
        dependency>

3.2.配置连接池属性

新增以下配置

spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.druid.filters=stat
spring.datasource.druid.max-active=20
spring.datasource.druid.initial-size=1
spring.datasource.druid.max-wait=60000
spring.datasource.druid.min-idle=1
spring.datasource.druid.time-between-eviction-runs-millis=60000
spring.datasource.druid.min-evictable-idle-time-millis=300000
spring.datasource.druid.validation-query=select 1
spring.datasource.druid.test-while-idle=true
spring.datasource.druid.test-on-borrow=true
spring.datasource.druid.test-on-return=true
spring.datasource.druid.pool-prepared-statements=true
spring.datasource.druid.max-open-prepared-statements=20

说明：以上配置不只是解决本文所述问题，还可以对连接池进行其他方面的优化，不再赘述。