mysql.sock 套接字文件丢失案例分析

数据库

mysql.sock 不存在的几种情况

• mysqld 错误启动
  
  • 非配置文件中指定的mysql用户运行mysqld
  • 配置文件或服务运行参数的指定目录 mysqld无权限
  • 配置参数异常，不存在
  • 进程重复占用文件未释放 冲突

本次异常属于第四种

定位分析开发环境大量数据库缺失 mysql.sock 文件的原因。目前定位是 在相应机器上部署了定时任务

*/1 * * * * /usr/local/mysql33066/start.sh &

导致 当数据库mysqld子进程异常退出，而父进程mysqld_safe仍未退出，但定时脚本同步运行拉起，其中运行了mysqld_safe，mysqld_safe同步再次拉起mysqld，导致mysqld启动错误，此时定时任务的mysqld_safe误将原父进程生成的mysql.scok清除

## 查看异常数据库对应的启动语句的进程号 以及sock文件是否创建
cat error.lock|grep -i 'start|sock'
# cat error.log |grep -E 'start|sock'
2020-04-02T17:27:24.406346+08:00 0 [Warning] No existing UUID has been found, so we assume that this is the first time that this server has been started. Generating a new UUID: 2954e695-74c4-11ea-a081-fa162647b44e.
2020-04-02T17:27:28.556365+08:00 0 [Note] /usr/local/mysql33066/bin/mysqld (mysqld 5.7.25-28-log) starting as process 2198 ...
2020-04-02T17:27:29.279269+08:00 0 [Note] InnoDB: Waiting for purge to start
2020-04-02T17:27:29.329502+08:00 0 [Note] InnoDB: Percona XtraDB (http://www.percona.com) 5.7.25-28 started; log sequence number 2529424
2020-04-02T17:27:29.361113+08:00 0 [Note] Server socket created on IP: '10.176.49.49'.
2020-04-02T17:27:29.424075+08:00 0 [Note] Failed to start slave threads for channel ''
Version: '5.7.25-28-log'  socket: '/usr/local/mysql33066/tmp/mysql.sock'  port: 33066  Source distribution
----------------------------
2020-08-10T03:00:03.552903+08:00 0 [Note] /usr/local/mysql33066/bin/mysqld (mysqld 5.7.25-28-log) starting as process 389369 ...
2020-08-20T17:55:06.158180+08:00 0 [Note] /usr/local/mysql33066/bin/mysqld (mysqld 5.7.25-28-log) starting as process 622502 ...
... ...
2021-02-04T17:12:03.651118+08:00 0 [Note] /usr/local/mysql33066/bin/mysqld (mysqld 5.7.25-28-log) starting as process 68198 ...
2021-02-04T17:12:04.706579+08:00 0 [Note] InnoDB: Waiting for purge to start
2021-02-04T17:12:04.756850+08:00 0 [Note] InnoDB: Percona XtraDB (http://www.percona.com) 5.7.25-28 started; log sequence number 602434766
2021-02-04T17:12:08.604898+08:00 0 [Note] Server socket created on IP: '10.176.49.49'.
2021-02-04T17:12:08.837762+08:00 0 [Note] Failed to start slave threads for channel ''
Version: '5.7.25-28-log'  socket: '/usr/local/mysql33066/tmp/mysql.sock'  port: 33066  Source distribution
2021-02-04T18:13:23.261404+08:00 0 [Note] /usr/local/mysql33066/bin/mysqld (mysqld 5.7.25-28-log) starting as process 91869 ...
## ps -ef 查看当前子进程的进程号，同时可以查看对应进程有些版本是有的mysql.sock.lock文件的创建日期
查看可发现 当前子进程的进程号仍是2198 可发现在未正常处理退出mysqld_safe之前的进程一直停留在了2198
-rw------- 1 mysql mysql 6 2020 ? mysql.sock.lock
### 中间的过程均是由于进程冲突 导致的重启失败 error log频繁显示冲突
[ERROR] InnoDB: Unable to lock ./ibdata1 error: 11
2021-02-04T18:13:23.650882+08:00 0 [Note] InnoDB: Check that you do not already have another mysqld process using the same InnoDB data or log files.