数据库事务耗时过长导致Could not retrieve transaction read-only status from server异常

[11-06 02:02:09:005] [ERROR] - DruidDataSource - discard connection
java.sql.SQLException: Could not retrieve transaction read-only status from server
 
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
 
The last packet successfully received from the server was 1,114,012 milliseconds ago.  The last packet sent successfully to the server was 1 milliseconds ago.
 
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.

wait_timeout 设置过小，mysql自动丢弃连接，但是程序端没有超时，造成依然在这个被丢弃的连接上执行语句

设置mysql wait_timeout 参数
show global variables like '%timeout%';
SET GLOBAL wait_timeout=86400;
此处的单位应该秒。