knowledgebase/linux/miscapplications/monit service monitoring {link:Monit|http://www.tildeslash.com/monit/} is an application service monitor. It can tell you if your MySQL or Apache server has crashed, and even give it a swift kick to get it up and going again. Compared to other service monitors I've looked at, Monit has good {link:documentation|http://www.tildeslash.com/monit/doc/}, and a straightforward configuration. It's available as a Debian package and there is an RPM here: http://dag.wieers.com/rpm/packages/monit/ On Debian, it won't start automatically after installing: {code} apt-get install monit Reading \package lists... Done Building dependency tree... Done The following NEW packages will be installed: monit 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 0B/255kB of archives. After unpacking 680kB of additional disk space will be used. Selecting previously deselected \package monit. (Reading database ... 58858 files and directories currently installed.) Unpacking monit (from .../monit_1%3a4.8.1-2.1_i386.deb) ... Setting up monit (4.8.1-2.1) ... Starting daemon monitor: monit won't be started/stopped unless it it's configured please configure monit and then edit /etc/\default/monit and set the \"startup\" variable to 1 in order to allow monit to start {code} In /usr/share/doc/monit/README.Debian, your find some information about creating a monit_delay script to prevent monit from restarting services that are slow to come up on reboot. Now all you need to do is go uncomment some things in the configuration file. You'll find that in /etc/monit/monitrc, or if you use the RPM, it's /etc/monit.conf There are many options for configuring monit, here is what I uncommented to get a simple configuration working: {code} set daemon 120 set logfile syslog facility log_daemon set mailserver localhost set alert root@localhost set httpd port 2812 and use address localhost # only accept connection from localhost allow localhost # allow localhost to connect to the server and allow admin:stR0Ngpsswd # require user 'admin' with password 'monit' {code} Instead of putting services in this same file, put them in /etc/monit.d, that way it's easy to turn off/on monitoring for a particular service. 1 Restart Apache For testing Apache's status, it's standard practice to create an empty file or 'token' for Monit to request. On Debian {code} mkdir /\var/www/monit/ touch /\var/www/monit/token {code} Paste this in your Apache configuration: {code} SetEnvIf Request_URI \"^\/monit\/token$\" dontlog CustomLog logs/access.log common env=!dontlog {code} Then paste this in /etc/monit.d/apache.conf {code} start program = \"/etc/init.d/apache2 start\" stop program = \"/etc/init.d/apache2 stop\" \if failed host 127.0.0.1 port 80 protocol HTTP request /monit/token then restart \if 5 restarts within 5 cycles then timeout {code} Then edit /etc/default/monit {code} # You must set \this variable \for monit to start startup=1 {code} Startup monit {code} /etc/init.d/monit start {code} check that it's running and then for fun, lets stop apache: {code} ps aux | grep monit root 11583 0.0 0.7 20400 1248 ? Sl 04:20 0:00 /usr/sbin/monit -d 180 -c /etc/monit/monitrc -s /var/lib/monit/monit.state /etc/init.d/apache2 stop {code} In syslog you'll see something like this: {code} Jun 18 04:32:41 rimu monit[11583]: HTTP error: Server returned status 404 Jun 18 04:32:41 rimu monit[11583]: 'apache2' failed protocol test [HTTP] at INET[127.0.0.1:80] via TCP Jun 18 04:32:41 rimu monit[11583]: 'apache2' trying to restart Jun 18 04:32:41 rimu monit[11583]: 'apache2' stop: /etc/init.d/apache2 Jun 18 04:32:42 rimu monit[11583]: 'apache2' start: /etc/init.d/apache2 {code} You can find many other configuration examples for MySQL, Mongrel and other popular applications, just google them up. 1 watch nginx {code} check process nginx with pidfile /var/run/nginx.pid start program = "/etc/init.d/nginx start" stop program = "/etc/init.d/nginx stop" if failed port 80 protocol HTTP request / then restart if 5 restarts with 5 cycles then timeout {code} 1 watch mongrels http://www.igvita.com/blog/2006/11/07/monit-makes-mongrel-play-nice/ http://software.pmade.com/blogs/ramblings/2006/12/27/mongrel-cluster-and-monit http://rubyforge.org/pipermail/mongrel-users/2006-September/001359.html 1 watch a VirtualHost or remote URL {code} check host arbitrary_name with address real_url if failed port 80 proto http then alert {code} See the man page for more examples. 2007-12-05 23:21:39.0 2007-06-18 16:57:25.0