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Heroku, Ruby on Rails and PhantomJS

#Heroku, Ruby on Rails and PhantomJS

In this post, I’m going to show you how to modify an existing Ruby on Rails app running on Heroku’s Cedar stack to use PhantomJS for screen scraping. If you’ve never heard of PhantomJS, it’s a command-line WebKit-based browser (that supports JavaScript, cookies, etc.).

Let’s get started. This is a high-level overview of the required steps:

  • Modify your app to use multiple Heroku buildpacks.
  • Extend your app to use both the Ruby as well as the PhantomJS buildpacks.
  • Confirm that everything worked.

David Dollar has created Heroku buildpack that allows you to use multiple Heroku buildpacks for your app. ;-) Install it by setting an environment variable:

$ heroku config:set BUILDPACK_URL=

Extend your app to use both the Ruby as well as the PhantomJS buildpacks

Create a .buildpacks file in the root directory of your app:

$ touch .buildpacks

Within your .buildpacks file, specify that your app uses both the Ruby and the PhantomJS buildpacks. This prevents you from having to (cross-)compile PhantomJS yourself. Make the contents of your .buildpacks file:

PhantonJS has a dependency on, which the PhantomJS buildpack installs on Heroku in/app/vendor/phantomjs/lib. Modify your Heroku app’s LD_LIBRARY_PATH to include this directory:

$ heroku config:set PATH="/usr/local/bin:/usr/bin:/bin:/app/vendor/phantomjs/bin"
$ heroku config:set LD_LIBRARY_PATH=/usr/local/lib:/usr/lib:/lib:/app/vendor/phantomjs/lib

Confirm that everything worked

First things first - load your app in your web browser and confirm that it still comes up. :-) Next, launch a Heroku bash shell:

$ heroku run bash

Within the bash shell, invoke the PhantomJS executable to ensure that it runs:

$ vendor/phantomjs/bin/phantomjs —version

Good to go! Now you’re ready to call PhantomJS from your Ruby code.

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Apologies in advance if this is way out of scope, but after following these directions successfully, I'm still unclear on how I'd actually execute Phantomjs commands within a Rails controller on Heroku. I've spent hours googling and on Stack Overflow to no avail but feel I'm missing something obvious.

How do I reference phantomjs from within my Rails app and then use Rails to execute Phantomjs commands? Thank you!!

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First you need to add the 3rd party phantomjs build pack.

Follow the instructions, deploy and check that it installs and that your app still works.

Then you need to get something that can run Phantom for you. Capybara and the Poltergeist gems are what you need. Install the gems and read the instructions.

After you've done that, just use the Capybara instructions in Ruby..

I've got it working. This article will show you how to do it.

My advice is to run it in a Rake task first to work out what's going on and then migrate.

Hope that helps!

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JHFirestarter commented Apr 23, 2016

@edelpero @benbowden @tomgallagher watir+phantomjs still does not work for me. I followed all of the above: web dyno is on & running, app is up, Multipack is my framework, and my buildpack in Heroku. I config'd the paths above.

On my local terminal, seems good: vendor/phantomjs/bin/phantomjs -v => 2.1.1
In heroku bash, not so much: vendor/phantomjs/bin/phantomjs -v => bash: vendor/phantomjs/bin/phantomjs: cannot execute binary file: Exec format error

I tried running a rake task heroku run rake example_task and received Selenium::WebDriver::Error::WebDriverError: unable to connect to phantomjs @ after 20 seconds

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Hey great tutorial. I found it because I "lowercased the p" in Procfile!

Now even when I rename it or create a new file I can not get heroku to see it. When I push it to github it is still lowercase.

Any idea how I can fix this?


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Don't need to do any of this anymore.


Simply do
heroku buildpacks:add --index 1

And deploy. Worked for me on Phantom 2.1.1

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mdkarp commented Sep 20, 2016

thanks @noafroboy worked for me!

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Also you can download the phamtomjs package and extract the executable in the bin folder, then you put it in the bin folder in your Rails app.

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