Hosting a Flask + Bokeh Server app in Heroku

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@Bryan, @p-himik,
I was able to host the Flask + Bokeh Server app within one Herokup app. No NGINX or Apache or any other external appliances needed.

Approach Used:

  1. I configured the jinja2 template to inject CDN resource scripts instead of the Bokeh static/js that is set up by default, using a custom function to create those scripts based on the local installed Bokeh version. Perhaps this can be optimized a bit by using Bokeh Resources class.

  2. From @p-himik hint, I wrapped the Flask application to run under Tornado.

  3. I used the Flask framework to create an HTTP reverse-proxy server (only supports GET method at this time.) However, this worked until I started receiving Web Socket requests.

  4. Finally, I created a Web Socket reverse-proxy for each connection opened by a client (browser) using Tornado web sockets. This part was the most challenging as I had to create/use multiple tools and code using the async programming approach from Tornado.

Results:

  1. I was expecting a bit of latency, but for my pleasant surprise redirecting the static/js resources to use CDN improved responsiveness quite a bit.
  2. This solution doesn’t require a second app in Heroku or build a complex reverse-proxy using Apache or NGINX.
  3. Where security is no a concern, it provides a frame work for development and test.
  4. Eases quite a bit integration concerns with the major frameworks with almost everything done on the user side in Python.

Code:

  1. I have this app currently running at https://safe-scrubland-67589.herokuapp.com/
  2. Code is at covid/app/utest at master · hmanuel1/covid · GitHub

I’m sure that I’m missing a couple of components. For example, I see in the Bokeh code support for POST, but I would like to understand how is used before I add support for it. I would like to contribute to the project, could you send me information to participate.

I would like to post the code in here, but it’s a project with several files. I see an “upload” option in this post. Please let me know where is the best way.

Thanks and keep the great work!
hmanuel1

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