Simple HTTP monitor

Monitor.md

POC simple HTTP monitoring script. First build the docker images:

git clone [this-gist] monitor
cd monitor
docker build -t amirkdv/monitor .

Now start the container, and all sites under sites.yaml will be pinged one after another:

docker run -i -t amirkdv/monitor
# Example 1 (immediate 200):
#   connecting to http://www.bbc.co.uk/
#   final HTTP code: 200
#   ---> UP
# Example 2 (DNS resolves, but site is down):
#   connecting to http://muhc-dev.tree.ewdev.ca/
#   Timeout
#   ---> DOWN: sending e-mail to admin@example.com
# Example 3 (DNS does not resolve):
#   connecting to http://nonexiting.muhc.ca
#   Timeout
#   ---> DOWN: sending e-mail to admin@example.com
# Example 4 (requires redirection to get to 200):
#   connecting to http://google.ca
#   redirecting (HTTP code: 301)
#   final HTTP code: 200
#   ---> UP
# Example 5 (URL contains query):
#   connecting to http://reuters-demo.tree.ewdev.ca:9090/reuters/select?q=a
#   final HTTP code: 200
#   ---> UP
# Example 6 (URL contains illegal query resulting in 403):
#   connecting to http://reuters-demo.tree.ewdev.ca:9090/reuters/
#   final HTTP code: 403
#   ---> DOWN: sending e-mail to admin@example.com
# Example 7 (HTTP basic auth):
#   connecting to http://sync-dev.tree.ewdev.ca
#   final HTTP code: 200
#   ---> UP
# Example 8 (HTTP basic auth, invalid credentials):
#   connecting to http://sync-dev.tree.ewdev.ca
#   final HTTP code: 401
#   ---> DOWN: sending e-mail to admin@example.com

Dockerfile

FROM ubuntu:12.04

ENV DEBIAN_FRONTEND noninteractive
# RUN echo 'Acquire::http::Proxy "http://172.17.42.1:8000";' > /etc/apt/apt.conf.d/30squid-deb-proxy

# Install Ruby
RUN apt-get update
RUN apt-get install -y ruby-full build-essential libxml2-dev libxslt-dev

# Install Exim
RUN echo "exim4-config exim4/dc_eximconfig_configtype select internet site; mail is sent and received directly using SMTP" | debconf-set-selections
RUN apt-get install -y exim4

# configure container
RUN mkdir -p /var/monitor
ADD . /var/monitor/
WORKDIR /var/monitor
CMD ["ruby", "/var/monitor/monitor.rb"]

monitor.rb

#!/usr/bin/env ruby

require 'yaml'
require 'net/http'
require 'timeout'

SITES_DEF = './sites.yaml'
INTERVAL  = 5*60
ADMIN = 'someone@example.com'

def ping(site)
  uri = URI.parse(site['URI'])
  http = Net::HTTP.new(uri.host, uri.port)
  req = Net::HTTP::Get.new(uri.request_uri)
  if credentials = site['credentials']
    req.basic_auth(credentials['username'], credentials['password'])
  end
  http.request(req)
end

def monitor
  sites = YAML.load_file(SITES_DEF)
  sites.each do |site|
    puts site['name'] + ':'
    available = false
    begin
      Timeout.timeout(10) do
        puts "  connecting to #{site['URI']}"
        res = ping(site)
        while (res.code == '302' || res.code == '301')
          puts "  redirecting (HTTP code: #{res.code})"
          site['URI'] = res.header['location']
          res = ping(site)
        end
        available = (res.code =='200')
        puts "  final HTTP code: #{res.code}"
      end
    rescue Timeout::Error
      puts "  Timeout"
    rescue SocketError => e
      puts "  Uri not resolved"
    end
    if available
      puts "  ---> UP"
    else
      puts "  ---> DOWN: sending e-mail to #{ADMIN}"
      mail_log = site['name'].gsub(/[^A-Za-z0-9-]/, '_').downcase + '_mail.log'
      cmd = "echo 'Subject: #{site['name']} is down' | sendmail -v #{ADMIN} >> #{mail_log} 2>&1"
      system(cmd)
    end
  end
end

loop do
  monitor
  sleep INTERVAL
end

sites.yaml

- name: Example 1 (immediate 200)
  URI:  http://www.bbc.co.uk/
- name: Example 2 (DNS resolves, but site is down)
  URI:  http://muhc-dev.tree.ewdev.ca/
- name: Example 3 (DNS does not resolve)
  URI:  http://nonexiting.muhc.ca
- name: Example 4 (requires redirection to get to 200)
  URI:  http://google.ca
- name: Example 5 (URL contains query)
  URI:  http://reuters-demo.tree.ewdev.ca:9090/reuters/select?q=a
- name: Example 6 (URL contains illegal query resulting in 403)
  URI:  http://reuters-demo.tree.ewdev.ca:9090/reuters/
- name: Example 7 (HTTP basic auth)
  URI:  http://sync-dev.tree.ewdev.ca
  credentials:
    username: evolvingweb
    password: evolvingweb
- name: Example 8 (HTTP basic auth, invalid credentials)
  URI:  http://sync-dev.tree.ewdev.ca
  credentials:
    username: incorrect
    password: incorrect