Librato Services

Service hooks for Librato Metrics.

Service Lifecycle

1. When a request to create a service is received by the API, the API calls the method receive_validate for the appropriate service class.
2. The service receive_validate method should validate the settings parameters. This method should return false with a set of invalid parameters if the settings are not correct for the service type.
3. Later, when a metric measurement is posted to the API that exceeds a configured alert threshold, the API records the exception.
4. A background job checks every minute for any alerts that have been triggered.
5. If any alerts have been triggered, the background job generates a POST to https://<services-server>/services/<service_name>/alert.json with the post data:
   • params[:settings]: the options the user specified in the Service configuration
   • params[:payload]: the event data for the triggered alert
6. A sinatra app lib/librato_services/app.rb decodes the request and dispatches it to a registered service if it exists

Writing a Service

All services are found in the services/ directory. They must have a method named receive_alert that is called when an alert is matched.

The settings are available as a Hash in the instance method settings and the event payload is available as a Hash in the instance method payload.

Tests should accompany all services and are located in the services/ directory.

Payload

A sample payload is available at [lib/librato-services/helpers/alert_helpers.rb] and listed below:

'payload' : {
        'alert' : {
                'name' : 'Alert name or nil',
                'id' : 12345,
        },
        'metric' : {
                 'name' : 'Name of the metric that tripped alert',
                 'type' : 'gauge' or 'counter',
        },
        'measurement' : {
                 'value' : 4.5 (value that caused exception),
                 'source' : 'r3.acme.com' (source that caused exception
                                           or 'unassigned')
        }
}

Sample Service

Here's a simple service that posts the measurement value that triggered the alert.

class Service::Sample < Service
  def receive_validate(errors = {})
    if settings[:name].to_s.empty?
      errors[:name] = "Is required"
      return false
    else
      return true
    end
  end

  def receive_alert
    value = payload[:measurement][:value]

    http_post 'https://sample-service.com/post.json' do |req|
      req.body = {
        settings[:name] => value
      }
    end
  end
end

Contributing

Once you've made your great commits:

1. Fork librato_services
2. Create a topic branch — git checkout -b my_branch
3. Commit the changes without changing the Rakefile or other files unrelated to your enhancement.
4. Push to your branch — git push origin my_branch
5. Create a Pull Request or an Issue with a link to your branch
6. That's it!

Credits

This project is heavily influenced in spirit and code by papertrail-services and github-services. We love what GitHub has done for all of us and what they have demonstrated can be accomplished with community involvement.

We thank them for everything they've done for all of us.