Mercy

This gem tries to make server monitoring easier and more reliable by adding an easly configurable report and making it avaliable in a controller

https://www.rubydoc.info/gems/mercy/1.6.0

1. Add Mercy to your Gemfile and bundle install:

   gem 'mercy'

2. Include in your health check controller passing the configuration to fetch your Documents with error and render the report

class HealthCheckController < ApplicationController
  include Mercy

  status_report :failures, clazz: Document
  status_report :failures, clazz: Schedules, on: :schedules
  status_report :delays, clazz: Schedules, scope: :late, on: :schedules
  status_report :'documents.count', clazz: Document, scope: :active, type: Mercy::Range, minimum: 100
  status_report :'documents.errors', clazz: Document, scope: :'active.with_error', type: :range, maximum: 1000

  def status
    render_status
  end

  def late_status
    render_status(:schedules)
  end
end

3. Add a route to your controller

scope path: 'health-check', controller: :health_check do
  get '/status' => :status
  get '/late-status' => :late_status
end

3. Set the correct options on your status report to achieve a perfect report

• clazz: Class of the object that might contain error
• period: default search period (default: 1 day)
• on: report bucket (default: :default)
• type: report type (error, range or other custom report)

Remembering that each report may have its onw parameters

• Mercy::Report::Error
  • scope: scope to be fetched when trying to find objects with error (default: :with_error)
  • external_key: column to be exposed as id for the objects with error
  • threshold: default report threshold (default: 0.02)
  • base_scope: scope to be universal sample
  • uniq: when the output ids should not be repeated
  • limit: limit of ids to be outputed
• Mercy::Report::Range
  • scope: scope of the query to be counted
  • maximum: max value accepted in the range
  • minimum: minimum value accepted in the range

4. Run the server and hit the health-check routes

wget http://localhost:3000/health-check/status
wget http://localhost:3000/health-check/late-status

5. Customize your request for multiple reports

wget http://localhost:3000/health-check/status?period=3.days&threshold=0.005
wget http://localhost:3000/health-check/late-status?period=1.hours&threshold=0.1

6. Use the status json to understand what is wrong

{
  "status": "error",
  "failures": {
    "ids": [10, 14],
    "percentage": 0.5,
    "status": "error"
  },
  "delays": {
    "ids": [12],
    "percentage": 0.001,
    "status": "ok"
  }
}