2012-02-11 10:35:19 by jdixon
I recently found myself in the need for a way to run a one-off Ruby script at scheduled intervals. As this is a work project I didn't just want to run it on my laptop or some random server. Turns out there's an easy way to run this for free on the Heroku Cedar platform without having to piggyback it on a "real" application. Because there are no web processes running, we'll be able to limit our dyno usage to a single dyno (in other words, it's free).
The script itself handles garbage collection duties for removing expired hosts off our beta account with Boundary. Basically I just want it to run every hour and cull anything that hasn't reported to their collectors in a day. For the purpose of this article the contents of the script are inconsequential, although I intend to present it fully in a future post.
$ cd oscar $ ls -l total 16 -rw-r--r-- 1 jdixon jdixon 47 Feb 11 09:25 Gemfile -rw-r--r-- 1 jdixon jdixon 189 Feb 11 09:25 Gemfile.lock bin: total 8 -rw-r--r-- 1 jdixon jdixon 954 Feb 11 09:25 purge_meters
You'll want to initialize your git repo (if you haven't already) and commit. Create a new Heroku app and add push it to the Heroku git server.
$ git init . Initialized empty Git repository in /Projects/oscar/.git/ $ git add . $ git ci -m "initial commit" [master (root-commit) 41ec621] initial commit 3 files changed, 56 insertions(+), 0 deletions(-) create mode 100644 Gemfile create mode 100644 Gemfile.lock create mode 100644 bin/purge_meters $ heroku create -s cedar Creating blooming-robot-7955... done, stack is cedar http://blooming-robot-7955.herokuapp.com/ | [email protected]:blooming-robot-7955.git Git remote heroku added $ git push heroku master Counting objects: 6, done. Delta compression using up to 2 threads. Compressing objects: 100% (4/4), done. Writing objects: 100% (6/6), 1002 bytes, done. Total 6 (delta 0), reused 0 (delta 0) -----> Heroku receiving push -----> Ruby app detected -----> Installing dependencies using Bundler version 1.1.rc.7 Running: bundle install --without development:test --path vendor/bundle --binstubs bin/ --deployment Fetching gem metadata from http://rubygems.org/.. Installing json (1.6.4) with native extensions Installing mime-types (1.17.2) Installing rest-client (1.6.7) Using bundler (1.1.rc.7) Your bundle is complete! It was installed into ./vendor/bundle Cleaning up the bundler cache. -----> Discovering process types Procfile declares types -> (none) Default types for Ruby -> console, rake -----> Compiled slug size is 1.5MB -----> Launching... done, v4 http://blooming-robot-7955.herokuapp.com deployed to Heroku To [email protected]:blooming-robot-7955.git * [new branch] master -> master
Next, add the Scheduler addon to your app.
$ heroku addons:add scheduler:standard -----> Adding scheduler:standard to blooming-robot-7955... done, v5 (free) This add-on consumes dyno hours, which could impact your monthly bill. To learn more: http://devcenter.heroku.com/addons_with_dyno_hour_usage To manage scheduled jobs run: heroku addons:open scheduler
Now you'll need to specify the task you want to run (your Ruby script). Run the following command to open the Scheduler dashboard in your default web browser.
$ heroku addons:open scheduler Opening scheduler:standard for blooming-robot-7955...
Click the Add Job... link to edit your task command. For my task I wanted to run the script with bundle exec ruby. Choose your Frequency, optionally select the Next Run time, and then Save. Once this is saved you can also click the Run button to run the job manually and look for any errors in the Task Output.
Voila, you have your own free cron job running through the wonders of THE CLOUD. Now go off and conquer the world!
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