Heroku have recently announced support for Web Sockets. They have provided a selection of code examples in various languages to illustrate the two-way communication enabled by web sockets. The focus of this article is the Python-Websockets-Chat application.
Provided is a walk-through for producing an app that will work on Heroku, taking advantage of the redis add-on that will be part of your infrastructure when your environment is created at set up. I wanted to get a better understanding of Python, Flask and the web sockets plugin, Gevent, so I needed to play with the application locally. This required some help from Vagrant. I've been over the benefits of Vagrant before in a similar article so no need to repeat myself.
The pre-requisites to having a running instance of the Python-Websockets-Chat application are numerous and complicated. Starting with a fresh Ubuntu Precise32 Vagrant box will take at least 15 minutes of install time to correctly configure the environment. Thankfully, the provisioning capabilities of Vagrant mean that we can kick off the 'Vagrant up' command in the project directory and just wait for the bootstrap shell script to do its thing.
The shell script is shown below. As you can see there are not only dependencies on python development tools and Pip - the Python plugin manager, but Ruby also. This is because the application is designed to run on Heroku which uses a Procfile to organise the processes that need deploying. Procfiles are best executed by a Ruby gem called Foreman, hence the dependency. Other than that there is the requirement to install and kick off Redis, followed by the Foreman start command to trigger the app into action. It should be available on your host machine at http://localhost:5000/.
Please see my forked repo of the chat app for all the code in one place.
Anyone with some experience in Linux will recognise a lot of this as incredibly basic instructions, understandably. This post is for the benefit of the Windows folk who have next to no knowledge of configuring Linux environments and just want to see results. That's part of Vagrant's goal, to simplify and centralize environment configuration, so I hope that this goes some way to helping that cause.
P.s. Windows users be sure that the line endings of the bootstrap.sh are in the linux format (LF) and not the Windows format (CRLF). Cloning the repo may have adjusted your line endings so if you run into a problem when the bootstrap.sh tries to be executed then please see this issue on github.
We've started using Shopify's Dashing gem internally so we can publicise any moving figures people are interested in. You can go from zero to great-looking-dashboard in next to no time once you understand the API. The Dashing Wiki has enough documentation and the example dashboards that ship with it are enough to communicate the usage pattern.
This post is about the biggest stumbling block we had when starting out. We develop on Windows machines as most of what we do is .net. Dashing is a solution written in Ruby so we wanted to develop on a Linux OS as we would be deploying to Heroku to host our production dashboards.
Enter Vagrant. This a really neat tool that lets you script the creation of a virtual machine. The Vagrant script sits in the root of your project so that it is under source control and can be shared across the team. Simply open the command line at your project directory and enter vagrant up. Within minutes a virtual machine running Ubuntu in text only mode is started.
Vagrant takes care of automatically sharing the project folder on your host machine with the guest virtual machine, so that you can continue development as normal and just execute the code inside the virtual machine. The port 3030 is forwarded so that we can view the Dashboard on our local browser. This is the content of my Vagrantfile:
Vagrant.configure("2") do |config|
config.vm.box = "precise32"
config.vm.network :forwarded_port, guest: 3030, host: 3030
end
So now we have in waiting a virtual machine running our target operating system, with a synced folder and the ability to hit any website running inside of it. However, that's not quite enough for Dashing. We need to update the version of Ruby to 1.9.1 and add some other essential apps. Here are the necessary steps that might hopefully save someone a lot of time:
From the Windows command line:
c:\MyDashing> vagrant up
c:\MyDashing> putty
Configure putty correctly and ssh into the VM.
Log in with username: vagrant
Enter commands:
$ cd ../../
$ sudo apt-get update
$ sudo apt-get install ruby1.9.1-full -y
$ exit
Back in the Windows command line:
c:\MyDashing> vagrant reload
c:\MyDashing> putty
Again, ssh into the VM:
$ cd ../../
$ sudo apt-get install build-essential -y
$ sudo apt-get install nodejs -y
$ sudo gem install bundler --no-rdoc --no-ri
$ sudo gem install dashing --no-rdoc --no-ri
$ dashing new MyDashing
$ cd MyDashing
$ bundle install
$ dashing start
Now you have initialized a dashing project. You should be able to enter dashing start at the command prompt and not be met with any error messages. Navigate to http://localhost:3030/sample on your local machine and hey presto! Development can now continue on your local machine, while serving the dashboards via your virtual box.
Gotchas:
- Make sure you update your Gemfile with any gems used in any new job you create. Then don't forget to run bundle install at the prompt!
- Any private key files or other assets required by code should reside in the root of the project.
- Keep an eye on the output when running vagrant up as Vagrant will cleverly accomodate any conflicting forwarded ports. This can affect the ports you use to ssh into the VM and view the dashboard.
P.s. I'm aware of the provisioning facilities of Vagrant, including the capability of running all of the above through a shell script during construction of the VM. However, I couldn't get it to work without including the restart so I have just left the raw commands as a the guide for now. If/when I figure it out I will update the post. However, these steps only need to be run once per machine (not every time you run vagrant up) so you might find its just about tolerable as it is.
