MySQL Bugs: #73642: The agent should search in the datadir for the pid-file

Bug #73642	The agent should search in the datadir for the pid-file
Submitted:	19 Aug 2014 12:07	Modified:	30 Dec 2014 15:02
Reporter:	Daniël van Eeden (OCA)	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Enterprise Monitor: Agent	Severity:	S3 (Non-critical)
Version:	3.0.13.3026	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
The MEM agent connects to a monitored database instance and does something like "select @@pid_file" to find the pid-file.

This works if the pid_file is an absolute path (/path/to/mysqld.pid), but not if it is a relative path (mysqld.pid)

This is used if mysqld and/or mysqld_safe is not running with --datadir and other options required to match a monitored instance with an instance found in the processlist.

If running with an pid-file with a relative path:
WARN com.mysql.etools.agent.collection.mysql.MysqlProcessProvider: Unable to read PID file: mysqld.pid (No such file or directory) 

How to repeat:
Run /some/location/mysqld --defaults-file=/foo/my.cnf
The my.cnf must have "pid_file=mysqld.pid"
Then start an mem agent.

Suggested fix:
If the path is relative it should serch in @@datadir for the pid file.

Thank you for the bug report. Verified based on internal discussion with dev's.

With mcm (MySQL Cluster Manager) 1.3.3 mysqld is started as child of mcmd and not via mysqld_safe. Then mem can also have issues with finding the pid.

$ ptree $(pgrep -x mcmd)
24427 /foo/mcmd --pl
  24626 /bar/bin/ndbd --ndb-connectstring=mysql1:1186 --nd
  24675 /bar/bin/mysqld --defaults-file=/baz/