systemctl start mysqld fails with timeout if socket isn't specified

[Marcelo Altmann]

This seems a regression / partial fix of https://bugs.launchpad.net/percona-server/+bug/1534825

Problem:
On RHEL 7, If socket variable isn't specified on my.cnf and datadir is set to a non-standard location, Percona-Server will create a socket on /var/lib/mysql/mysql.sock.
pinger function from /usr/bin/mysql-systemd will read proxy variable from my.cnf. This will return none. Then it will try to check proxy in 3 locations:

        /*) adminsocket="$socket" ;; -- not set
        "") adminsocket="$datadir/mysql.sock" ;; -- $datadir is on a non standard location and socket has been created on /var/lib/mysql/mysql.sock
        *) adminsocket="$datadir/$socket" ;; -- $socket is empty.

Start or restart mysql service via systemctl will fail due to timeout:
[root@localhost data]# systemctl restart mysql
Job for mysqld.service failed because a timeout was exceeded. See "systemctl status mysqld.service" and "journalctl -xe" for details.

root@localhost data]# mysql --socket=/var/lib/mysql/mysql.sock
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.52-38.3 Percona Server (GPL), Release 38.3, Revision 109ad68

Copyright (c) 2009-2016 Percona LLC and/or its affiliates
Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

[root@localhost data]# cat /etc/my.cnf | grep socket
[root@localhost data]# cat /etc/my.cnf | grep datadir
datadir=/mysql/data

How to reproduce:
1) Install Percona-Server
2) Change datadir location on my.cnf
3) Remove socket configuration from my.cnf
4) run systemctl [re]start mysql

[Muhammad Irfan (muhammad-irfan)]

I'm able to reproduce this problem. The mysql-systemd post fails to ping when you don't have explicitly set a socket in my.cnf.

$ sh -x /usr/bin/mysql-systemd post
+ case $socket in
+ adminsocket=/data/db/data/mysql.sock
+ /bin/true
+ sleep 1
+ mysqladmin --socket=/data/db/data/mysql.sock ping
+ /bin/true
+ sleep 1
+ mysqladmin --socket=/data/db/data/mysql.sock ping
+ /bin/true
+ sleep 1
+ mysqladmin --socket=/data/db/data/mysql.sock ping
+ /bin/true
+ sleep 1
^C

Socket file doesn't exist in data directory:

$ ls -ltr /data/db/data/mysql.sock
ls: cannot access /data/db/data/mysql.sock: No such file or directory

After adding following line in [mysqld] section in my.cnf file

socket=/var/lib/mysql/mysql.sock

Here is the output of mysql-systemd post after explicitly setting socket file in my.cnf:

$ sh -x /usr/bin/mysql-systemd post
+ socket=/var/lib/mysql/mysql.sock
+ case $socket in
+ adminsocket=/var/lib/mysql/mysql.sock
+ /bin/true
+ sleep 1
+ mysqladmin --socket=/var/lib/mysql/mysql.sock ping
+ break
+ exit 0

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-1755