Moodle Prometheus reporting endpoint

A local plugin that presents an endpoint for Prometheus metric gathering. Can be used either in Prometheus or as an InfluxDB v2 scraper

Developing

Plugins can add their own metrics to the output by adding their own plugin_name_prometheus_get_metrics(int $window) function to lib.php. This function must return either one or more \local_prometheus\metric objects, or an empty array. Plugins should give users the option to toggle metric gathering for that plugin on or off.

The $window parameter is a unix timestamp and is used for determining the cutoff for a 'current' value. For example to determine the number of currently online users we can only look at the last access timestamp. In this case, $window would mean "treat users active since this timestamp as currently online".

Example implementation in lib.php:

/**
 * Fetch metrics for the plugin
 *
 * @param int $window
 * @return metric[] 
 */
mod_example_prometheus_get_metrics(int $window): array {
    $metric = new metric(
        'moodle_mod_example_foo',
        metric::TYPE_GAUGE,
        'optional HELP text, can be omitted'
    );
    
    $metric->add_value(new metric_value(
        [ 'label' => 'foo' ],
        12
    ));
    
    return [ $metric ];
}

Installation

The plugin requires Moodle 3.9 or later, and PHP 7.4 or later. You will also need some way of gathering, storing, and using the metrics that the plugin generates.

There's no special installation steps or instructions, just install it as you would any other plugin

Install from Moodle.org

• Download .zip file from https://moodle.org/plugins/local_prometheus
• Navigate to /moodle/root/local
• Extract the .zip to the current directory
• Go to your Moodle admin control panel, or php /moodle/root/admin/cli/upgrade.php

Install from git

• Navigate to your Moodle root folder
• git clone https://github.com/Vidalia/moodle-local_prometheus.git local/prometheus
• Make sure that user:group ownership and permissions are correct
• Go to your Moodle admin control panel, or php /moodle/root/admin/cli/upgrade.php

Install from .zip

• Download .zip file from GitHub
• Navigate to /moodle/root/local/prometheus
• Extract the .zip to the current directory
• Rename the moodle-local_prometheus-master directory to prometheus
• Go to your Moodle admin control panel, or php /moodle/root/admin/cli/upgrade.php