Pi-crossbar

This application drives a LED via a raspberry pi.
To better understand the crossbar concept, I divided this project into 4 parts.
In the last part, the user is able to drive the LED from any platform (mobile device, computer, etc).
For example, from my office I can drive the LED (and then the raspberry pi) which is located in my house.

Overview:

• Step 1: Understand the role of each node
• Step 2: Add a new RPC
• Step 3: See the crossbar node dependance
• Step 4: Use Heroku, a cloud platform as a service (PaaS)
• Heroku CLI helper

Step 1: Understand the role of each node

release: https://github.com/HBevilacqua/Pi-crossbar/releases/tag/v20161014pm

• cloud = local network
• all nodes are hosted on the Raspeberry Pi itself
• the web application uses crochet
• the backend implements a remote procedure, add2(x, y)
• the web app can call this procedure because it is connected to the same router and realm.

Figure 1: step 1 diagram

Sources:

backend.py/frontend.py forked from https://github.com/HBevilacqua/crossbar_template

webapp.py forked from https://github.com/crossbario/autobahn-python/blob/224370cd9dda312fc0583b61ed416b3f4d0e00d0/examples/twisted/wamp/app/crochet/example1/server.py

templates/home.html forked from https://github.com/crossbario/autobahn-python/blob/224370cd9dda312fc0583b61ed416b3f4d0e00d0/examples/twisted/wamp/app/crochet/example1/client.html

Step 2: Add a new RPC

release: https://github.com/HBevilacqua/Pi-crossbar/releases/tag/v20101020step2

• cloud = local network
• add the remote procedure to blink the raspberry pi LED

Step 3: See the crossbar node dependance

release: https://github.com/HBevilacqua/Pi-crossbar/releases/tag/v20161020step3

• cloud = local network
• the crossbar router is no longer hosted by the raspberry pi but by another node (for example my computer)
• you have to set the CROSSBAR_ROUTER_ADDRESS environment variable with the new crossbar ip address before launching the backend.py and the webapp.py

Step 4: Use Heroku, a cloud platform as a service (PaaS)

1. Deploy your owm crossbar router through Heroku

Note: You have to create your account on Heroku.

• Go to https://github.com/AndreMiras/crossbar-hello-python-to-heroku.git
• Click on the "Deploy to Heroku" button
• Give a name to your node, ex: "crossbarnode"
• Your app can be found at https://crossbarnode.herokuapp.com/

2. The backend runs on the raspberry pi to drive the LED

Update the ROUTER_ADDRESS environment variable according to the crossbar node:

$ export ROUTER_ADDRESS=wss://crossbarnode.herokuapp.com/ws 

start the backend:

python backend.py

3. The flask application (frontend) runs also on Heroku

Note: If you do not wish start your webapp from scratch, use a template forked from https://github.com/AndreMiras/flask-autobahn-to-heroku.git and follow the README instructions to start/shutdown your Heroku application.

Create a new git repository:

$ cd flask_app_on_heroku
$ git init
$ git add .
$ git commit -m "Initial commit"

Heroku uses a Procfile to determine what commands to use to start your app:

echo "web: gunicorn webapp:app" > Procfile

Download and extract the Heroku client tarball:

$ wget https://s3.amazonaws.com/assets.heroku.com/heroku-client/heroku-client.tgz
$ tar -xvzf heroku-client.tgz --directory ~/bin/
$ echo 'export PATH="${PATH}:~/bin/heroku-client/bin/"' >> ~/.bashrc
$ . ~/.bashrc

Create the app on Heroku (ex: https://warm-shore-87822.herokuapp.com/):

$ heroku create

Design your webapp, commit your local changes...
Deploy and start the app:

$ git push heroku master
$ heroku config:set ROUTER_ADDRESS=wss://crossbarnode.herokuapp.com/ws

4. The web browser runs on my mobile phone

Once the crossbar/webapp runs on Heroku and the backend on your Raspberry pi, open a web browser and visit the web page to use the application.

Figure: Step 4 diagram

Heroku CLI helper

The name of my webapp dyno is "web", see the Procfile.

Log in using the email address and password you used when creating your Heroku account:

$ heroku login

Create an app:

$ heroku create

See your apps:

$ heroku apps

Scale up (start) an app:

$ heroku ps:scale --app your-app-name web=1

Scale down (stop) an app:

$ heroku ps:scale --app your-app-name web=0

Check an app activity:

$ heroku ps --app your-app-name

Run/See one-off dynos in action, execute the bash command

$ heroku run bash --app warm-shore-87822

In bash mode, exit/shut down the current one-off dyno

$ exit

see also: https://devcenter.heroku.com/articles/using-the-cli