cloudwatch_scheduler

CloudwatchScheduler

Are you using Rails 4.2+ and ActiveJob with the Shoryuken driver to use SQS? Do you have recurring jobs that you kick off periodically with the amazing Clockwork gem? Tired of paying for a Heroku dyno just to run the clockwork instance? Then CloudwatchScheduler is just the gem for you!

CloudwatchScheduler uses AWS Cloudwatch scheduled event rules to push a message on the cloudwatch_scheduler queue according to the schedule you provide, using a simple DSL similar to the Clockwork DSL you're already familiar with. The rules are free, and the messages cost a few billionths of a cent each, saving you over $25/mo in Heroku dyno costs! Wow!!

And thats not all! It will automatically provision the Cloudwatch Events and Queues via a simple rake task! Amazing!

Installation

Add this line to your application's Gemfile:

gem 'cloudwatch_scheduler'

And then execute:

$ bundle

Or install it yourself as:

$ gem install cloudwatch_scheduler

Usage

Make yourself a config/cloudwatch_schedule.rb file:

require "cloudwatch_scheduler"

CloudwatchScheduler do |config|

  # 4am every day
  task "spawn_analytics_jobs", cron: "0 4 * * ? *" do
    return if Rails.application.config.deploy_env.sandbox?
    AnalyticsSpawnerJob.perform_later
  end

  task "capture_pg_stats", every: 5.minutes do
    PgHero.capture_query_stats
  end

end

You'll also need to inform Shoryuken about the cloudwatch_scheduler queue, either in the config/shoryuken.yml or with -q cloudwatch_scheduler on the command line.

Then do rake cloudwatch_scheduler:setup, and CloudwatchScheduler will provision the events and cloudwatch_scheduler queue. Then, start your Shoruken workers as normal, and the CloudwatchScheduler::Job will get those events, and perform the tasks defined.

IAM Permissions

The setup task requires some permissions in the AWS account to create the queue and Cloudwatch Events. Here's a sample policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "sqs:CreateQueue",
        "sqs:GetQueueAttributes",
        "sqs:SetQueueAttributes",
      ],
      "Resource": [
        "arn:aws:sqs:REGION:AWS_ACCOUNT:cloudwatch_scheduler",
        "arn:aws:sqs:REGION:AWS_ACCOUNT:cloudwatch_scheduler-failures"
      ]
    },
    {
      "Effect": "Allow",
      "Action": [
        "events:PutRule",
        "events:PutTargets"
      ],
      "Resource": [
        "*"
      ]
    }
  ]
}

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/paul/cloudwatch_scheduler.