场景：一个上传接口，需要上传几十M的文件，文件中包含10几W的数据，然后对10+W的数据进行同步批量插入，每次批量插入1W。最后返回结果。
项目上线一段时间后，上传接口出现问题，数据库用的MySQL5.7.21，报了如下错误：
2018-07-16 01:30:03.497 ERROR com.alibaba.druid.pool.DruidDataSource Line:1594 - discard connection
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet successfully received from the server was 1,480 milliseconds ago. The last packet sent successfully to the server was 1,480 milliseconds ago.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
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:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3603)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3492)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4043)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2503)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2664)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2815)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1379)
at com.alibaba.druid.pool.DruidPooledPreparedStatement.execute(DruidPooledPreparedStatement.java:498)
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 com.github.pagehelper.PageInterceptor.intercept(PageInterceptor.java:137)
at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:61)
at com.sun.proxy.$Proxy63.query(Unknown Source)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
at sun.reflect.GeneratedMethodAccessor102.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:434)
at com.sun.proxy.$Proxy25.selectList(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:231)
at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:137)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:75)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53)
at com.sun.proxy.$Proxy51.selectReportListByReportDate(Unknown Source)
at com.rxwx.service.report.impl.PrcmtReportServiceImpl.generateProcurementReport(PrcmtReportServiceImpl.java:97)
at com.rxwx.service.report.impl.PrcmtReportServiceImpl$$FastClassBySpringCGLIB$$f325780.invoke()
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:720)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:280)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:655)
at com.rxwx.service.report.impl.PrcmtReportServiceImpl$$EnhancerBySpringCGLIB$$8c585594.generateProcurementReport()
at com.rxwx.service.report.impl.PrcmtReportServiceImpl$$FastClassBySpringCGLIB$$f325780.invoke()
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:720)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:280)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:655)
at com.rxwx.service.report.impl.PrcmtReportServiceImpl$$EnhancerBySpringCGLIB$$9a830f32.generateProcurementReport()
at com.rxwx.task.sup.GenarateReportJob.selfGenReportTask1(GenarateReportJob.java:37)
at com.rxwx.task.sup.GenarateReportJob$$FastClassBySpringCGLIB$$64b31449.invoke()
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:720)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.aop.interceptor.AsyncExecutionInterceptor$1.call(AsyncExecutionInterceptor.java:115)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
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:3052)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3503)
... 58 common frames omitted 首先百度了一发，按照网上的解决方案，修改了my.cnf中的超时时间：
wait_timeout=31536000
interactive_timeout=31536000将原来默认的8小时改为1年。这里单位是秒。
修改了德鲁伊的：testOnBorrow = true。
跑了一天，MMP，凌晨又出现这个错误了。
一个电话把睡梦中的我吵醒，扰我周末扰我梦，没得办法，重启下服务，重启下MySQL，先上传吧，睡觉。
周一到公司谷歌了一发，修改my.cnf的net_read_timeout和net_write_timeout 参数，将这两个参数调大，改为6000。由于项目中的数据存在无效数据，所以删除了10天之前的无效数据，减少了表中的数量。明天看效果。
show global variables like "%timeout%";
connect_timeout
连接超时 mysql连接共有6次握手，3次TCP协议这个跟connect_timeout参数没有关系，另外3次跟connect_timeout参数有关系，该参数主要是为了防止网络不佳时应用重连导致连接数涨太快，一般默认即可。
delayed_insert_timeout
这是为MyISAM INSERT DELAY设计的超时参数，在INSERT DELAY中止前等待INSERT语句的时间
interactive_timeout
服务器关闭交互式连接前等待活动的秒数。交互式客户端定义为在mysql_real_connect()中使用CLIENT_INTERACTIVE选项的客户端。参数默认值：28800秒（8小时）
lock_wait_timeout
锁等待超时时间
net_read_timeout / net_write_timeout
这个参数只对TCP/IP链接有效，分别是数据库等待接收客户端发送网络包和发送网络包给客户端的超时时间，这是在Activity状态下的线程才有效的参数
slave_net_timeout
这是Slave判断主机是否挂掉的超时设置，在设定时间内依然没有获取到Master的回应就人为Master挂掉了
wait_timeout
服务器关闭非交互连接之前等待活动的秒数。
效果很明显。今天没有出现问题。