Bug #84172 The pid-file value is ignored in the /etc/my.cnf option file

Description:
The pid-file value in the /etc/my.cnf file is being ignored. It appears that the mysqld script ignores the pid-file entry in the [mysqld] section of the /etc/my.cnf file and provides its own default value.

Various sections of the documentation indicate that the pid-file entry in the [mysqld] section would be used.

6.1.4 Server Command Options
https://dev.mysql.com/doc/refman/5.7/en/server-options.html

5.3.2 mysqld_safe — MySQL Server Startup Script
https://dev.mysql.com/doc/refman/5.7/en/mysqld-safe.html

5.3.3 mysql.server — MySQL Server Startup Script
https://dev.mysql.com/doc/refman/5.7/en/mysql-server.html

The documentation for systemd states that it doesn't use the pid-file in the [mysqld] section but RHEL/CentOS 6 uses mysqld and not systemd.

https://dev.mysql.com/doc/refman/5.7/en/using-systemd.html
2.5.10 Managing MySQL Server with systemd

How to repeat:
* Add a pid-file entry to only the [mysqld] section in /etc/my.cnf. Use a file name other than /var/run/mysqld/mysqld.pid

[mysqld]
pid-file = /tmp/monty.pid

* Start mysqld

service mysqld start

* Observe that the pid file used is /var/run/mysqld/mysqld.pid even though a different name was specified.

# ps -ef | grep mysql

/bin/sh /usr/bin/mysqld_safe ... --pid-file=/var/run/mysqld/mysqld.pid ...
/usr/sbin/mysqld ... --pid-file=/var/run/mysqld/mysqld.pid ...

* Examine the mysqld script and observe that it looks for the pid-file entry in the [mysqld_safe] section but not in the [mysqld] section.

# grep pid /etc/init.d/mysqld
get_mysql_option mysqld_safe pid-file "/var/run/mysqld/mysqld.pid"

Suggested fix:
Fix the mysqld script to read the pid-file from the [mysqld] section.

Hi,

Thanks for your report.

The pid is set by the "starting" app so not by the mysqld itself so the pid-file parameter is not in the [mysqld] section but in [mysqld-safe] section as mysqld_safe is what's setting it. So this is behaving as expected really and is not a bug.

If you feel strongly that our documentation is not clear enough how this works and where it goes you can create a documentation bug but with regards to this one the pid-file is not moving from [mysqld] to [mysqld-safe]

Take care
Bogdan

The documentation states that the [mysqld] section is widely read but the /etc/init.d/mysqld startup script is limiting itself to just the [mysqld_safe] section when looking for the pid file.

The documentation for the startup script states that the startup script reads the [mysqld] option file group but not the [mysqld_safe] group.

Here are the relevant excerpts.

Server Command Options
https://dev.mysql.com/doc/refman/5.7/en/server-options.html

mysqld reads options from the [mysqld] and [server] groups. mysqld_safe reads options from the [mysqld], [server], [mysqld_safe], and [safe_mysqld] groups. mysql.server reads options from the [mysqld] and [mysql.server] groups.

MySQL Server Startup Script
https://dev.mysql.com/doc/refman/5.7/en/mysql-server.html

Because mysql.server reads the [mysqld] option file group but not the [mysqld_safe] group

The documentation states in both of those sections that the startup script does not read from the [mysqld_safe] section but we can see that it is explicitly doing so.

# grep mysqld_safe /etc/init.d/mysqld 

get_mysql_option mysqld_safe log-error "/var/log/mysqld.log"
get_mysql_option mysqld_safe pid-file "/var/run/mysqld/mysqld.pid"

Hi,

Yes, as I said, it's documentation fault not server fault.

This parameter should be in the [mysqld-safe] section and not inside [mysqld] section, and yes it will not be used with systemd nor by any other starting system other then mysqld_safe (hence it's in mysqld-safe section).

I changed the bug category and verified it. When documentation team get to it they'll probably remove the problematic part of the text from our documentation

take care
Bogdan

I figured out why the pid file in the [mysqld] section used to work.

Oracle provides two different distributions of MySQL 5.6 for RHEL 6 and they use two different startup scripts (with different names). The mysql startup script in MySQL-server honors the pid file specified in the [mysqld] section of the /etc/my.cnf file. The mysqld startup script in the mysql-community-server does not honor the pid file specified in the [mysqld] section of the /etc/my.cnf file.

MySQL-server-5.6.35-1.el6.x86_64.rpm is available from the download section of the MySQL web site.

mysql-community-server-5.6.35-2.el6.x86_64.rpm is available in the yum repository.

# tar xvpf MySQL-5.6.35-1.el6.x86_64.rpm-bundle.tar

# rpm -ivf MySQL-*5.6.35*rpm --force

# rpm -qa | grep ^MySQL
MySQL-client-5.6.35-1.el6.x86_64
MySQL-shared-5.6.35-1.el6.x86_64
MySQL-devel-5.6.35-1.el6.x86_64
MySQL-test-5.6.35-1.el6.x86_64
MySQL-shared-compat-5.6.35-1.el6.x86_64
MySQL-server-5.6.35-1.el6.x86_64
MySQL-embedded-5.6.35-1.el6.x86_64

mysql  Ver 14.14 Distrib 5.6.35, for Linux (x86_64) using  EditLine wrapper
Server version:		5.6.35-log MySQL Community Server (GPL)

mysql> select @@pid_file;
+--------------------------------+
| @@pid_file                     |
+--------------------------------+
| /opt/mysql/dbprod/monty-q0.pid |
+--------------------------------+
1 row in set (0.00 sec)

root     15558     1  0 11:33 pts/1    00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/opt/mysql/dbdata1/monty-q0 --pid-file=/opt/mysql/dbprod/monty-q0.pid

mysql    17206 15558  0 11:33 pts/1    00:00:00 /usr/sbin/mysqld --basedir=/usr --datadir=/opt/mysql/dbdata1/monty-q0 --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/opt/mysql/dblogs1/monty-q0/gen/error.log --open-files-limit=65535 --pid-file=/opt/mysql/dbprod/monty-q0.pid --socket=/opt/mysql/dbprod/monty-q0.sock --port=3306

# yum install mysql-community-*5.6.35*

# rpm -qa | grep ^mysql-community
mysql-community-devel-5.6.35-2.el6.x86_64
mysql-community-libs-compat-5.6.35-2.el6.x86_64
mysql-community-libs-5.6.35-2.el6.x86_64
mysql-community-client-5.6.35-2.el6.x86_64
mysql-community-embedded-5.6.35-2.el6.x86_64
mysql-community-test-5.6.35-2.el6.x86_64
mysql-community-bench-5.6.35-2.el6.x86_64
mysql-community-common-5.6.35-2.el6.x86_64
mysql-community-server-5.6.35-2.el6.x86_64
mysql-community-embedded-devel-5.6.35-2.el6.x86_64

mysql  Ver 14.14 Distrib 5.6.35, for Linux (x86_64) using  EditLine wrapper
Server version:		5.6.35-log MySQL Community Server (GPL)

mysql> select @@pid_file;
+----------------------------+
| @@pid_file                 |
+----------------------------+
| /var/run/mysqld/mysqld.pid |
+----------------------------+
1 row in set (0.00 sec)

root     20529     1  0 11:41 pts/1    00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/opt/mysql/dbdata1/monty-q0 --socket=/opt/mysql/dbprod/monty-q0.sock --pid-file=/var/run/mysqld/mysqld.pid --basedir=/usr --user=mysql

mysql    22221 20529  0 11:41 pts/1    00:00:01 /usr/sbin/mysqld --basedir=/usr --datadir=/opt/mysql/dbdata1/monty-q0 --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/opt/mysql/dblogs1/monty-q0/gen/error.log --open-files-limit=65535 --pid-file=/var/run/mysqld/mysqld.pid --socket=/opt/mysql/dbprod/monty-q0.sock --port=3306

Posted by developer:
 
Noted in 5.5.55, 5.6.36, 5.7.18, 8.0.1 changelogs.

For System V init scripts for RPMs, the [mysqld] option-file section
was being ignored for some options, such as pid-file.