Description

Users may find that the QFabric backup DG shows a suspicious ""ERROR! MySQL is not running, but PID file exists" error message as the MySQL process status in QFX Series devices. Even though the "MySQL is not running" message is expected, the "PID file exists" message could cause confusion.

This article clarifies that the error does not have any major impact and details how to clear the PID file message.

Symptoms

When MySQL is running only on the primary Director Group device of QFabric, the MySQL status on the backup DG should display the following message: 

[root@dg1 ~]# date; service mysql status
Wed Apr 28 04:10:15 UTC 2021
ERROR! MySQL is not running

However, in some cases, the following message is displayed, which may lead to misinterpretation and customer concern. 

[root@dg1 ~]# date; service mysql status
Wed Apr 28 04:10:15 UTC 2021
ERROR! MySQL is not running, but PID file exists

Solution

The error message does not have any major impact, but the "PID file exists" message may lead to confusion. To clear this message, remove the backup PID file from the location " /pbdata/usr/mysql-5.5.28/data/ " as shown below:

Note: In this example, we have used DG0 as the primary and DG1 as the backup device.

  1. Find the backup DG PID file from " /pbdata/usr/mysql-5.5.28/data/ ."   

[root@dg1 ~]# date; ls -l /pbdata/usr/mysql-5.5.28/data/ | grep pid
Wed Apr 28 04:10:55 UTC 2021
rw-rw---- 1 mysql         6 Apr 23 03:07 dg0.pid
-rw-rw---- 1 mysql         6 Apr 23 01:40 dg1.pid <<<<< backup DG pid file

  1. Remove the backup DG PID file. 

[root@dg1 ~]# rm -rf /pbdata/usr/mysql-5.5.28/data/dg1.pid

  1. Check the MySQL status in the backup DG: 

[root@dg1 ~]# date; service mysql status
Wed Apr 28 04:11:36 UTC 2021
ERROR! MySQL is not running
[root@dg1 ~]#