passenger-prometheus-exporter-app

Small application that runs on the Phusion Passenger webserver and exposes Passenger metrics in a Prometheus format.

Metrics

Name	Description
passenger_capacity	Number of processes spawn
passenger_processes_active	Number of processes currently working on requests
passenger_wait_list_size	Requests in queue

Example of output:

# HELP passenger_capacity Capacity used
# TYPE passenger_capacity gauge
passenger_capacity{supergroup_name="/app (development)",group_name="/app (development)",hostname="my-container"} 1
# HELP passenger_wait_list_size Requests in the queue
# TYPE passenger_wait_list_size gauge
passenger_wait_list_size{supergroup_name="/app (development)",group_name="/app (development)",hostname="my-container"} 0
# HELP passenger_processes_active Active processes
# TYPE passenger_processes_active gauge
passenger_processes_active{supergroup_name="/app (development)",group_name="/app (development)",hostname="my-container"} 0

Requirements

• a Ruby interpreter in the path
• the Nokogiri gem (tested with 1.10.0)
• the Sinatra gem (tested with 2.0.5)

Integration

Copy the content of src inside your container (or your server) and adapt the Nginx configuration template to load the application:

Example with the application copied in /monitor:

# Modified nginx.conf.erb

    [...]
        ### END your own configuration options ###
    }

    <% end %>

    server {
        server_name _;
        listen 0.0.0.0:10254;
        root '/monitor/public';
        passenger_app_root '/monitor';
        passenger_app_group_name 'Prometheus exporter';
        passenger_spawn_method direct;
        passenger_enabled on;
        passenger_min_instances 1;
        passenger_load_shell_envvars off;
    }

    <%= include_passenger_internal_template('footer.erb', 4) %>
    [...]

This example will make the Passenger Metric available on http://<ip-of-this-server>:10254/metrics.

Note: If you want to have this application's metrics hidden from the metric endpoint, you have to name its group Prometheus exporter.

Development

This project uses Docker and Docker Compose for testing. make test will build a test container with a dummy applicaton and the Prometheus Exporter and query the metric endpoint. If all goes well, hack along and submit a pull request.