Send AWS EC2 maintenance notification to Slack

0-screenshot.md

ec2-maintenance-checks.rb

#!/usr/bin/env ruby
require 'aws-sdk'
require 'digest'
require 'json'

AWS_REGION = "us-east-1"
S3_BUCKET = "<YOUR BUCKET>"
SLACK_COMPANY = "<YOUR COMPANY>"
SLACK_TOKEN = "<YOUR TOKEN>"
SLACK_CHANNEL = "#ops"

EC2 = Aws::EC2::Client.new(region: AWS_REGION)
S3 = Aws::S3::Client.new(region: AWS_REGION)

def run_once(deduplication_id)
  S3.head_object({
    bucket: S3_BUCKET,
    key: deduplication_id,
  })
rescue Aws::S3::Errors::NotFound
  S3.put_object({
    bucket: S3_BUCKET,
    key: deduplication_id,
    body: "1",
  })
  yield
end

def get_name_for_instance_id(instance_id)
  EC2.describe_instances({
    instance_ids: [instance_id]
  }).reservations.first.instances.first.tags.select { |x| x.key == "Name" }.first.value
rescue
  "<empty name>"
end

EC2.describe_instance_status({
  filters: [
    {
      name: "event.code",
      values: %w{instance-reboot system-reboot system-maintenance instance-retirement instance-stop},
    },
  ]
}).instance_statuses.each do |x|
  id = x.instance_id
  name = get_name_for_instance_id(id)
  x.events.each do |event|
    code = event.code
    description = event.description
    not_before = event.not_before || "<empty time>"
    not_after = event.not_after || "<empty time>"
    summary = "[`#{code}`] between #{not_before} - #{not_after}"
    json = {
      username: "ec2 maintenance check",
      icon_emoji: ":ghost:",
      channel: SLACK_CHANNEL,
      text: "New maintenance event for *#{name}*",
      fallback: "New maintenance event for #{name}",
      attachments: [{
        color: "#ff4136",
        fields: [
          {
            title: "Description",
            value: description,
            short: false
          },
          {
            title: "Instance ID",
            value: id,
            short: true
          },
          {
            title: "Code",
            value: code,
            short: true
          },
          {
            title: "Not Before",
            value: not_before,
            short: true
          },
          {
            title: "Not After",
            value: not_after,
            short: true
          }
      ],
      }]
    }
    deduplication_id = "#{id}-#{code}"
    run_once(deduplication_id) do
      system "curl -s -d 'payload=#{JSON.dump(json)}' 'https://#{SLACK_COMPANY}.slack.com/services/hooks/incoming-webhook?token=#{SLACK_TOKEN}'"
    end
  end
end