数据库Communications link failure

1.出现错误查询 Error querying , Communications link failure

#Error querying database.Cause:com.mysql.cj.jdbc.exceptions.CommunicationsException:Communications link failure
The last packet successfully received from the server was 10,016 milliseconds ago.
The last packet sent successfully to the server was 10,030 milliseconds ago.

结合当时场景, 有很多查询到某一个表的任务都在进行中, 其他表查询正常, 只要涉及到该表的查询, 就会连接失败

2.使用的是MySQL数据库, 排查数据库查询超长连接

SELECT * FROM information_schema.processlist 
WHERE command = 'Sleep' AND time > 30;

当时发现有很多time在六七千, 占用连接,

3.直接KILL + ID释放掉, 后续连接正常

KILL ID