Implementing a /healthcheck endpoint in Slack to read out consul status in a human-readable fashion

app_controllers_slack_controller.rb

class SlackController < ApplicationController
  skip_before_action :verify_authenticity_token

  @@slack_security_tokens =
   ["copy-paste-the-token-you-get-from-Slack-when-configuring-the-integration-here"]

    before_filter :bounce_access_not_from_slack

  def healthcheck
    services = SystemStatus.list_services
    if services.blank?
      render json: {
        response_type: "in_channel",
        text: "PlayerUI couldn't connect successfully to consul cluster.  BAD NEWS."
      }
    else
      arguments = params[:text]
      node_filter = nil
      if arguments.present? && services.include?(arguments.split(" ")[0])
        # /healthcheck gm <-- Filters results down to only gm nodes
        services = [arguments.split(" ")[0].strip]
      elsif arguments.present? && (arguments.split(" ")[0].present?)
        # /healthcheck 172.31.16.60 <-- Filters results down to only this IP.
        node_filter = arguments.split(" ")[0].strip
      end
      response = []
      services.each do |service|
        status = SystemStatus.service_up?(service)
        status_string = status ? "[UP]" : "[*DOWN*]"
        nodes = SystemStatus.list_service_nodes(service)
        node_details = []
        nodes.each do |node|
          tags = (node[:tags].length < 10) ? node[:tags].join("|") : (node[:tags][0..9].join("|") + "...")
          detail = "#{node[:address]}:#{node[:port]} (#{tags})"
          detail = "~#{detail}~" unless SystemStatus.service_up?(service, node[:tags].first)
          node_details << detail if node_filter.blank? || (node_filter == node[:address])
        end
        response << [service, status_string, node_details].join(" ") if node_filter.blank? || node_details.present?
      end

      render json: {
        response_type: "in_channel",
        text: response.join("\n")
      }
    end 
    
  private

  def bounce_access_not_from_slack
    unless Rails.env.development? || @@slack_security_tokens.include?(params[:token])
      raise "Not authorized: token sent doesn't match pre-configured Slack security token."
    end
  end
  
end

app_models_system_status.rb

require 'resolv'

class SystemStatus

  def self.list_services
    services = JSON.parse(RestClient.get("http://localhost:8500/v1/catalog/services")) rescue nil
    services ? services.keys : nil
  end

  def self.list_service_nodes(service)
    nodes = JSON.parse(RestClient.get("http://localhost:8500/v1/catalog/service/#{service}")) rescue []
    nodes.map do |node|
      node[:address] = node["ServiceAddress"].present? ? node["ServiceAddress"] :  node["Address"]
      node[:port] = node["ServicePort"] || (node["Port"] || "0").to_i
      node[:tags] = node["ServiceTags"] || []
      node[:node] = node["Node"]
    end
    nodes
  end

  def self.service_up?(service, tag = nil)
    if !tag
      (!!dns.getaddress("#{service}.service.consul")) rescue false
    else
      (!!dns.getaddress("#{tag}.#{service}.service.consul")) rescue false
    end
  end

  def self.node_up?(node)
     (!!dns.getaddress("#{node}.node.consul")) rescue false
  end

  def self.service_statuses(bust_cache = false)
    t = bust_cache ? nil : Time.now.to_i
    Rails.cache.fetch("SystemStatus.service_statuses(#{t})", :expires_in => 1.minute) do
      services = list_services

      services.inject({}) {|acc, service| acc[service] = service_up?(service) ? "up" : "down"; acc}
    end
  end


  def self.dns
    Resolv::DNS.new(nameserver: ["127.0.0.1"])
  end

end

license.txt

MIT license, same as Rails.  Feel free to hack the heck out of this.