Scout plugin for checking HTTP statuses on AWS EC2

ec2_http_health.rb

# EC2 Http servers health status
#  * Number of running instances
#  * Average response time

class Ec2HttpHealth < Scout::Plugin
  needs 'right_aws'
  needs 'timeout'

  OPTIONS=<<-EOS
  access_key_id:
    name: AWS Access Key ID    
  secret_access_key:
    name: AWS Secret Access Key    
  name_pattern:
    name: Name pattern on your EC2 instances
    default: app slave
  http_port:
    name: HTTP port to ping
    default: 81
  request_uri:
    name: URI to request
    default: /health/pulse
  EOS

  def check_status(host, port, uri)
    timer = Time.now
      http = Net::HTTP.new(host, port)
      request = Net::HTTP::Get.new(uri)
      response = http.request(request)
      response.is_a?(Net::HTTPOK)
    return response.is_a?(Net::HTTPOK), Time.now - timer
  end
  
  def build_report    
    pattern    = option(:name_pattern)
    port       = option(:http_port)
    uri        = option(:request_uri)
    
    connection = RightAws::Ec2.new(option(:access_key_id), option(:secret_access_key), :logger=>nil)
    instances_count  = 0
    timer = 0
    
    connection.describe_instances.each do |instance|
      name = instance[:tags]["Name"]
      public_dns = instance[:dns_name]
      
      if name.downcase.include?(pattern)        
        status_ok, time = check_status(public_dns, port, uri)        
        unless status_ok
          alert("Instance #{public_dns} is not working properly!") 
        else
          instances_count += 1
          timer += time
        end        
      end      
    end    
    
    report :instances_count => instances_count, :average_response_time => timer / instances_count
  end

end