Configuring Monit: A Gratis Organisation Monitoring Together With Recovery Tool

Why Monit?

One morning, I went on-line to depository fiscal establishment jibe my WordPress website. Lo together with behold, I saw this error: 'Error establishing a database connection.' My website had been downwards for four hours, luckily inwards the pump of the night.

I used a gratuitous website monitoring service called StatusCake. Sure enough, it did transportation me an e-mail alerting me virtually this problem. But, sending an e-mail at 2am was non helpful inwards solving the problem. What I actually needed was a tool that non entirely detected when the database physical care for went down, simply would also restart the physical care for without human intervention. Monit is such a tool.

For the residue of this post, I assume you lot desire Monit to monitor a LAMP server (Linux, Apache2, MySQL, PHP).

Install Monit.

To install Monit on Debian or Ubuntu, execute this command:

$ sudo apt-get install monit 

As role of the installation, a monit service is created:

$ sudo chkconfig --list | grep -i monit   monit       0:off  1:off  2:on   3:on   4:on   5:on   6:off 

Configure Monit

The primary Monit configuration file is /etc/monit/monitrc. To edit it, you lot necessitate sudo privileges.

$ sudo vi /etc/monit/monitrc 

After you lot brand a alter to the file, follow these steps to convey it into effect:

1. Validate configuration file syntax.

   $ sudo monit -t 

   If no mistake is returned, continue to adjacent step.

2. Restart Monit.

   $ sudo service monit restart 

Global settings

The cardinal global settings to customize are:

• Test interval

  By default, Monit checks your arrangement at 2-minute intervals. To customize the interval, alter the value (from 120) inwards the next statement. The unit of measurement of mensurate is seconds.

  set daemon 120 

• Log file place

  You tin specify whether Monit logs to syslog or a log file of your choice.

  # laid logfile syslog facility log_daemon   laid logfile /var/log/monit.log 

• Mail server

  Specify a transportation service server for Monit to transportation e-mail alerts. I gear upwardly exim4 every bit an SMTP server on the localhost. For instructions, refer to my previous post.

  set mailserver localhost 

• Email format

  Hopefully, you lot won't have many warning emails, simply when you lot do, you lot desire the maximum information virtually the potential problem. The default e-mail format contains all the information known to Monit, simply you lot may customize the format inwards which the information is delivered. To customize, exercise the set mail-format statement.

  set mail-format {       from:     monit@$HOST       subject:  monit warning --  $EVENT $SERVICE       message:  $EVENT Service $SERVICE                 at $DATE                 on $HOST                $ACTION                 $DESCRIPTION                 Your faithful employee,                 Monit   } 

  For a description of the set mail-format statement, click here.

• Global alerts

  If whatever actionable trial occurs, Monit sends an e-mail warning to a predefined address list. Each e-mail address is defined using the set alert statement.

  set warning root@localhost non on { instance, activity } 

  In the higher upwardly example, root@localhost is the e-mail recipient. Please refer to my before post virtually redirecting local emails to a remote e-mail account.

  Note that an trial filter is defined (not on { instance, activity }). Root@local volition have an e-mail warning on every trial unless it is of the instance or action type. An instance trial is triggered yesteryear the starting or stopping of the Monit process. An action trial is triggered yesteryear for sure explicit user commands, e.g., to unmonitor or monitor a service. Click here for the consummate listing of trial types that you lot tin exercise for filtering.

  By default, Monit sends an e-mail warning when a service fails together with about other when it recovers. It does non repeat failure alerts later the initial detection. You tin alter this default demeanor yesteryear specifying the reminder alternative inwards the set alert statement. The next illustration sends a reminder e-mail on every 5th evidence cycle if the target service remains failed:

  set warning root@localhost amongst reminder on v cycles 

• Enabling reporting together with service management

  You tin dynamically contend Monit service monitors, together with asking condition reports. These capabilities are delivered yesteryear an embedded spider web server. By default, this spider web server is disabled. To enable it, include the set httpd statement.

  set httpd port 2812 together with     exercise address localhost       permit localhost 

  Note: I've entirely allowed local access to the embedded spider web server. The Useful Commands department below explains the commands to asking reporting together with management services.

Resource monitor settings

The next are the cardinal resources to monitor on a LAMP server.

• System performance

  You tin configure Monit to transportation an warning when arrangement resources are running below for sure minimum surgical physical care for threshold. The arrangement resources that tin hold upwardly monitored are load averages, memory, swap together with CPU usages.

  check arrangement example.com      if loadavg (1min) > four       together with so warning    if loadavg (5min) > 2       together with so warning    if retentiveness usage   > 75%     together with so warning    if swap usage     > 25%     together with so warning    if cpu usage (user)   > 70% together with so warning    if cpu usage (system) > 30% together with so warning    if cpu usage (wait)   > 20% together with so warning 

• Filesystem usage

  You tin exercise a monitor which is triggered when the pct of disk infinite used is greater than an upper threshold.

  check filesystem rootfs amongst path /   if infinite usage > 90% together with so warning 

  You may accept to a greater extent than than i filesystem created on your server. Run the df ascendance to position the filesystem refer (rootfs) together with the path it was mounted on (/).

• MySQL

  Instead of putting the MySQL-specific statements inwards the primary configuration file, I elect to set them inwards /etc/monit/conf.d/mysql.conf. This is a personal preference. I similar a to a greater extent than compact primary configuration file. All files within the /etc/monit/conf.d/ directory are automatically included inwards Monit configuration.

  The next statements should hold upwardly inserted into the mysql.conf file.

  check physical care for mysql amongst pidfile /var/run/mysqld/mysqld.pid         foremost programme = "/etc/init.d/mysql start"         halt programme = "/etc/init.d/mysql stop"         if failed unixsocket /var/run/mysqld/mysqld.sock together with so restart         if v restarts within v cycles together with so timeout 

  If the MySQL physical care for dies, Monit needs to know how to restart it. The ascendance to foremost the MySQL physical care for is specified yesteryear the start program clause. The ascendance to halt MySQL is specified yesteryear the stop command clause.

  A timeout trial is triggered if MySQL is restarted v times inwards a bridge of v consecutive evidence cycles. In the trial of a timeout, an warning e-mail is sent, together with the MySQL physical care for volition no longer hold upwardly monitored. To resume monitoring, execute this command:

  $ sudo monit monitor mysql 

• Apache

  I set the next Apache-specific statements inwards the file /etc/monit/conf.d/apache.conf.

  check physical care for apache2 amongst pidfile /var/run/apache2.pid       foremost programme = "/etc/init.d/apache2 start"       halt programme = "/etc/init.d/apache2 stop"       if failed host example.com port lxxx protocol http asking "/monit/token" together with so restart       if three restarts within v cycles together with so timeout       if children > 250 together with so restart       if loadavg(5min) greater than 10 for viii cycles together with so halt 

  At every evidence cycle, Monit attempts to think http://example.com/monit/token. This URL points to a dummy file created on the webserver specifically for this test. You necessitate to exercise the file yesteryear executing the next commands:

  $ mkdir /var/www/monit $ impact /var/www/monit/token  $ chown -R www-data:www-data /var/www/monit 

  Besides testing spider web access, the higher upwardly configuration also monitors resources usages. The Apache physical care for is restarted if it spawns to a greater extent than than 250 kid processes. Apache is also restarted if the server's charge average is greater than 10 for viii cycles.

Useful commands

To impress a condition summary of all services beingness monitored, execute the ascendance below:

    $ sudo monit summary       The Monit daemon 5.4 uptime: 3h 48m       System 'example.com'                Running     Filesystem 'rootfs'                 Accessible     Process 'mysql'                     Running     Process 'apache2'                   Running 

To impress detailed condition information of all services beingness monitored, execute the following:

    $ sudo monit condition     The Monit daemon 5.4 uptime: 3h 52m       System 'example.com'       condition                            Running       monitoring condition                 Monitored       charge average                      [0.00] [0.01] [0.05]       cpu                               0.0%us 0.0%sy 0.0%wa       retentiveness usage                      377092 kB [74.0%]       swap usage                        53132 kB [10.3%]       information collected                    Wed, 22 April 2015 13:21:47     ...             Process 'apache2'       condition                            Running       monitoring condition                 Monitored       pid                               12909       bring upwardly pid                        i       uptime                            6d 15h 18m        children                          10       retentiveness kilobytes                  2228       retentiveness kilobytes total            335420       retentiveness percent                    0.4%       retentiveness percent total              65.9%       cpu percent                       0.0%       cpu percent total                 0.0%       port reply fourth dimension                0.001s to example.com:80/my-monit-dir/token [HTTP via TCP]       information collected                    Wed, 22 April 2015 13:21:47 

To unmonitor a especial service (e.g., apache2):

    $ sudo monit unmonitor apache2 

To unmonitor all services:

    $ sudo monit unmonitor all 

To monitor a service:

    $ sudo monit monitor apache2 

To monitor all services:

    $ sudo monit monitor all 

Conclusion

I'd recommend that you lot run Monit on your server inwards improver to signing upwardly for a remote website monitoring service such every bit StatusCake. While the 2 services exercise overlap, they also complement each other. Monit runs locally on your server, together with tin restart processes when a employment is detected. However, a networking employment may larn undetected yesteryear Monit. That is where a remote monitoring service shines. In the trial of a network failure, the remote monitor fails to connect to your server, together with volition so study a employment that may otherwise larn unnoticed.

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