一、问题描述

本来正常运行的Spring Boot项目突然报错

2020-05-10 11:57:10.054 [http-nio-8095-exec-3] ERROR com.alibaba.druid.pool.DruidPooledStatement - CommunicationsException, druid version 1.1.12, jdbcUrl : jdbc:mysql://dev001:3306/video_chat?useUnicode=true&characterEncoding=utf8&characterSetResults=utf8&useSSL=false&serverTimezone=Asia/Shanghai, testWhileIdle true, idle millis 36820, minIdle 0, poolingCount 0, timeBetweenEvictionRunsMillis 60000, lastValidIdleMillis 36820, driver com.mysql.cj.jdbc.Driver, exceptionSorter com.alibaba.druid.pool.vendor.MySqlExceptionSorter
2020-05-10 11:57:10.054 [http-nio-8095-exec-3] ERROR com.alibaba.druid.pool.DruidDataSource - discard connection

Caused by: com.mysql.cj.exceptions.CJCommunicationsException: The last packet successfully received from the server was 36,820 milliseconds ago.  The last packet sent successfully to the server was 36,820 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.
	at jdk.internal.reflect.GeneratedConstructorAccessor135.newInstance(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
	at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
	at com.mysql.cj.protocol.a.NativeProtocol.readMessage(NativeProtocol.java:555)
	at com.mysql.cj.protocol.a.NativeProtocol.checkErrorMessage(NativeProtocol.java:725)
	at com.mysql.cj.protocol.a.NativeProtocol.sendCommand(NativeProtocol.java:664)
	at com.mysql.cj.protocol.a.NativeProtocol.sendQueryPacket(NativeProtocol.java:979)
	at com.mysql.cj.NativeSession.execSQL(NativeSession.java:1153)
	at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:951)
	... 109 common frames omitted
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.cj.protocol.FullReadInputStream.readFully(FullReadInputStream.java:67)
	at com.mysql.cj.protocol.a.SimplePacketReader.readHeader(SimplePacketReader.java:63)
	at com.mysql.cj.protocol.a.SimplePacketReader.readHeader(SimplePacketReader.java:45)
	at com.mysql.cj.protocol.a.TimeTrackingPacketReader.readHeader(TimeTrackingPacketReader.java:52)
	at com.mysql.cj.protocol.a.TimeTrackingPacketReader.readHeader(TimeTrackingPacketReader.java:41)
	at com.mysql.cj.protocol.a.MultiPacketReader.readHeader(MultiPacketReader.java:54)
	at com.mysql.cj.protocol.a.MultiPacketReader.readHeader(MultiPacketReader.java:44)
	at com.mysql.cj.protocol.a.NativeProtocol.readMessage(NativeProtocol.java:549)
	... 114 common frames omitted

二、问题分析

1. mysql连接失败，看样子可以通过配置参数autoReconnect=true解决

三、问题原因

 1. 在使用mysql是的时候,如果超过默认8小时数据库没有操作，会自动断开连接，于是我查看测试服务器的连接超时时间居然是30s

mysql> show global variables like 'wait_timeout';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wait_timeout  | 30    |
+---------------+-------+
1 row in set (0.00 sec)

四、问题解决方案

1. set global variables wait_timeout=86400