Easymon

action_cable_connection_statistics.rb

# app/lib/easymon/action_cable_connection_statistics.rb

module Easymon
  class ActionCableConnectionStatistics
    def check
      count = ActionCable.server.open_connections_statistics.count
      status = count < 100

      [status, "#{status ? "low" : "high"} - #{count}"]
    rescue
      [false, "Down"]
    end
  end
end

easymon.rb

# config/initializers/easymon.rb

Rails.application.config.after_initialize do
  load Rails.root.join("app/lib/easymon/sidekiq_queue_size_check.rb")
  load Rails.root.join("app/lib/easymon/sidekiq_queue_latency_check.rb")
  load Rails.root.join("app/lib/easymon/action_cable_connection_statistics.rb")
end

Easymon::Repository.add(
  "database",
  Easymon::ActiveRecordCheck.new(ActiveRecord::Base),
  :critical
)
Easymon::Repository.add("redis",
  Easymon::RedisCheck.new(
    YAML.load(
      ERB.new(
        File.read(Rails.root.join("config/cable.yml"))
      ).result
    )[Rails.env].symbolize_keys
  ))

Easymon::Repository.add(
  "memcached",
  Easymon::MemcachedCheck.new(Rails.cache)
)

Easymon::Repository.add(
  "sidekiq queue size",
  Easymon::SidekiqQueueSizeCheck.new
)

Easymon::Repository.add(
  "sidekiq queue latency",
  Easymon::SidekiqQueueLatencyCheck.new
)

Easymon::Repository.add(
  "action cable connections",
  Easymon::ActionCableConnectionStatistics.new
)

Easymon::Repository.add(
  "metabase",
  Easymon::HttpCheck.new("https://metabase.codefund.io")
)

Easymon::Repository.add(
  "wordpress",
  Easymon::HttpCheck.new("https://codefund.io")
)

health_controller.rb

# app/controllers/health_controller.rb

class HealthController < ApplicationController
  def index
    checklist = Easymon::Repository.all
    checklist.check

    @results = []
    checklist.results.each do |key, value|
      @results << OpenStruct.new(name: key.titleize, success: value.success, message: value.message)
    end
  end
end

index.html.erb

# app/views/health/index.html.erb

<%= render "/shared/index_layout",
    title: "Health",
    sidebar: false do %>
  <div class="grid grid-tcolumns-200">
    <% @results.each do |result| %>
      <div class="metric metric-bordered">
        <h2 class="metric-label"> <%= result.name %> </h2>
        <p class="metric-value h2">
          <sup><%= result.success ? "✔️" : "✖️" %></sup> <span class="value"><%= result.message %></span>
        </p>
      </div>
    <% end %>
  </div>
<% end %>

routes.rb

# config/routes.rb

  resources :health, only: [:index]

sidekiq_queue_latency_check.rb

# app/lib/easymon/sidekiq_queue_latency_check.rb

module Easymon
  class SidekiqQueueLatencyCheck
    def check
      latency = Sidekiq::Queue.new.latency
      status = latency < 30

      [status, "#{status ? "ok" : "not-ok"} - #{latency}"]
    rescue
      [false, "Down"]
    end
  end
end

sidekiq_queue_size_check.rb

# app/lib/easymon/sidekiq_queue_size_check.rb

module Easymon
  class SidekiqQueueSizeCheck
    def check
      length = Sidekiq::Queue.all.sum(&:size)
      status = length < 25_000

      [status, "#{status ? "low" : "high"} - #{length}"]
    rescue
      [false, "Down"]
    end
  end
end

Thanks to @andrewmcodes 🙌