Monit

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app-admin/monit is a utility for managing and monitoring processes, programs, files, directories and filesystems on a UNIX system.

Конфигурация

Установка monit

У приложение app-admin/monit есть следующие USE-флаги:

USE flags for app-admin/monit Monitoring and managing daemons or similar programs running on a Unix system

Once the USE flags are properly determined, install app-admin/monit through emerge:

root #emerge --ask app-admin/monit

Конфигурационные файлы Monit

The Monit application uses /etc/monitrc as its configuration file.

To make adding and removing monitoring definitions easy, monit supports including files inside a specified directory (usually /etc/monit.d. To enable this, edit /etc/monitrc like so:

Файл /etc/monitrcAllowing flexible configuration entries
## It is possible to include additional configuration parts from other files or
## directories.
include /etc/monit.d/*

When a Monit related configuration file is altered, tell monit to reread its configuration settings:

root #monit reload

Автоматический старт monit во время загрузки

It is recommended to start monit through the /etc/inittab so that init itself launches the monit application, and will automatically relaunch it when monit would suddenly die. Starting monit through an init script would not provide this functionality.

Файл /etc/inittabAuto restart monit in case of failure
# Run monit in standard runlevels
mo:2345:respawn:/usr/bin/monit -Ic /etc/monitrc

After updating /etc/inittab, monit can be immediately started through telinit q.

Управление пользователями

Users added to the monit or users group will be able to manipulate monit through its web interface.

To add users to one of these groups, use gpasswd:

root #gpasswd -a $USER monit
root #gpasswd -a $USER users

Inside the /etc/monitrc file, the allow statement should refer to these groups, like so:

Файл /etc/monitrcGranting groups access to the web interface
set httpd port 2812
  allow @monit
  allow @users

It is also possible to hard-code usernames and passwords in the monitrc file, but this is not recommended. Check the monitrc file for default passwords and remove those, or alter them to use a strong, unique password. The syntax used then is allow <username>:<password>.

Веб-интерфейс monit

The default location of the web interface is at localhost:2812, with admin as admin username and monit as default password. Make sure to change this!

Monitoring applications through monit

The Monit application uses PID file checks to see if an application is still running or not. That implies that a PID file must be available for an application, otherwise monit cannot guard it. If a daemon does not create a PID file, use a wrapper to create one.

Заметка
The use of PID files (and validating PIDs from tools like ps) for monitoring is often said to be broken[1]. Monit does try to overcome this weakness by checking the PID file frequently enough to be reliable.

Through using the /etc/monit.d/ location, it is easy to add in additional monitoring rules.

For instance, to automatically restart MySQL when it would die:

Файл /etc/monit.d/mysqlАвтоперезагрузка mysql
check process mysql with pidfile /var/run/mysqld/mysqld.pid
    start program = "/bin/bash -c 'rc-service mysql start'"
    stop program  = "/bin/bash -c 'rc-service mysql stop'"

Another example is to manage the memory usage of a process and create an alert when it grows beyond a certain threshold:

Файл /etc/monit.d/squidCheck squid and alert on memory consumption bigger than 512 MByte
check process squid with pidfile /run/squid.pid
   start program = "/bin/bash -c 'rc-service squid start'"
   stop  program = "/bin/bash -c 'rc-service squid stop'"
   if totalmem > 512 MB then alert

Отладка monit

Running monit in the foreground

To run monit in the foreground and provide feedback on everything it is detecting, use the -Ivv option:

root #monit -Ivv
...
'squid' total mem amount of 525748kB matches resource limit [total mem amount>524288kB]

Внешние ресурсы

For more information about Monit, the following resources can help out.

Ссылки

  1. Greg Wooledge. Process management, Retrieved on January 1st, 2015