Moodle Nagios Monitoring

This is a Moodle plugin to simplify monitoring the Moodle service (as opposed to the hardware and infrastructure) using Nagios. It provides:

1. A simple API which allows plugins to implement "services" which can be monitored.
2. A Nagios plugin script (/cli/check_moodle) which communicates with the Moodle plugin to get service status into Nagios.
3. A couple of simple example services.
4. A simple admin page for the plugin available through Plugins -> Local plugins -> Nagios monitoring.
   • This simply displays the available services in order for administrators to configure Nagios to check them.

Note that this plugin is intended for experienced systems administrators who are familiar with both Moodle and Nagios configuration!

Documentation (Service API)

The local\_nagios plugin scans other Moodle plugins looking for a db/local_nagios.php file.

db/local_nagios.php

This should contain a single definition for a variable named "$services", which is an associative array of service name to definition. The definition is a key value pair containing at least the classname, and optionally params.

See the plugin's db/local_nagios.php file for examples.

Service class

The service class must extend the local\_nagios\service class and implement the check\_status() method.

The \local\_nagios\service object has constants for the status code, e.g. \local\_nagios\service::NAGIOS\_STATUS\_WARNING

Requirements

• Requires a PHP executable to be available on the server.
• Create or move symlink from local/nagios/cli/check_moodle to your Nagios plugins directory (e.g. CentOS /usr/lib64/nagios/plugins) with command ln -s /var/www/html/moodle /local /nagios/cli/check_moodle /usr/lib64/nagios/plugins/.
  • Additional: Edit the $MOODLE_DIR and (if necessary) the PHP location in the shebang line to reflect your environment.
• Change the permissions on the script to make it executable (chmod +x local/nagios/cli/check_moodle).
• Optional: Nagios NRPE agent (e.g. CentOS yum install nagios-plugins-all nrpe) if Nagios not running on the same server.

Installation

Install the plugin like any other plugin to folder local/nagios.

Use git to install this plugin:

cd /var/www/html/moodle
git clone https://github.com/ffhs/moodle-local_nagios.git local/nagios
echo '/local/nagios/' >> .git/info/exclude

Then complete upgrade over CLI:

sudo -u apache /usr/bin/php admin/cli/upgrade.php

or GUI (Site administration -> Notifications).

Configuration

CentOS

Create or update existing NRPE config file (e.g. CentOS /etc/nrpe.d/51_nrpe_additional_monitoring.cfg) and define new command:

command[check_moodle]=/usr/lib64/nagios/plugins/check_moodle -p=$ARG1$ -s=$ARG2$ -w=$ARG3$ -c=$ARG4$ -t=$ARG5$ -x=$ARG6$

Examples of Services in Nagios Core Config Manager:

// Check command
check_nrpe

// $ARG1$
check_moodle

// $ARG2$ (only one line per Service)
-a local_nagios cron 300 3600
-a local_nagios adhoc_task 100 200
-a local_nagios scheduled_task 100 200 /core/task/check_for_updates_task

Nagios can now execute the check_moodle command with the defined arguments.

---

Please be aware that if you are using SELinux you must run following commands, so that NRPE can execute the checks:

usermod -a -G apache nrpe
setfacl --modify group:apache:r-x /var/www/html/moodle/local/nagios/cli/check_moodle
semanage fcontext -a -t nagios_unconfined_plugin_exec_t /var/www/html/moodle/local/nagios/cli/check_moodle
restorecon -Frv /var/www/html/moodle/local/nagios/cli/check_moodle

// Not needed anymore.
#semodule -i /var/www/html/moodle/local/nagios/lib/local_nagios.pp

If you're not doing that, it will cause nrpe to output the NRPE: Unable to read output.

Ubuntu

1. Create a new file, moodle.cfg, in your Nagios plugins configuration directory (/etc/nagios-plugins/config).
2. Add a command definition for each Moodle service to be monitored, e.g.:

define command{
    command_name    check_moodle_cron
    command_line    /usr/lib/nagios/plugins/check_moodle -p=local_nagios -s=cron
}

Note the use of Moodle-style parameter passing (using =). Use these command in Nagios service definitions as normal.

Troubleshooting

Permission requirements

• The Nagios plugin calls the script lcoal/nagios/cli/check.php in the Moodle plugin. This means that the user account Nagios is running under must have write access to the Moodle data directory, otherwise all checks will result in an error message.
• If the user account Nagios is running under has to use sudo to call the PHP executable, this must be configured in the shebang line in the check_moodle script. The sudo access for the account must also be configured to be able to run the PHP executable without being challenged for a password.