You might recall that every time we ran our app, we got a warning telling us that when we want to make our website go live and go from development to production mode that we should use a WSGI server.

WSGI stands for Web Server Gateway Interface and it's described here: https://www.python.org/dev/peps/pep-3333/

It standardises the language and protocols between our Python Flask application and the host server.

Again, but in English: Normal web servers can't run Python applications, so a special type of server was created (WSGI) to run python applications.

There are many WSGIs to choose from, but we'll use the most popular - gunicorn.

So Heroku will call gunicorn to run our code and gunicorn will know how to speak to Heroku.

1. In PyCharm go to the Python Interpreter for your Project and install the gunicorn package:

Windows: Files -> Settings -> Project: blog-with-user -> Python Interpretor

Mac: PyCharm -> Preferences -> Project: blog-with-user -> Python Interpretor

Note: Make a note of the version of gunicorn you installed e.g.

2. Add the package to the requirements.txt file on a new line:

gunicorn==<version number>

NOTE: Your version number will be higher than mine because you are in the future.

Next, we need to tell Heroku about our gunicorn server and how to run our Flask app, we do that using a Procfile.

3. Create a new file in the project top-level folder called Procfile

NOTE: make sure you spell the name of the file exactly as you see above, with a capital P and no file extension.

Type the following into the Procfile:

web: gunicorn main:app

This will tell Heroku to create a web worker, one that is able to receive HTTP requests.

To use gunicorn to serve your web app

And the Flask app object is the main.py file.

NOTE: If your app is not inside a file called main.py then you should change main to your file name.

4. Add the new Procfile/requirements.txt to git and commit the changes then push it to the remote.

Note: If you forgot to "Commit and Push" and just clicked on "Commit" then just go to VSC -> Git -> Push

Because we enabled automatic re-deploys, if you go to your app's logs you should see it being re-built an re-deployed with the changes we have pushed to GitHub.

All going well, you should now be able to go to your app and see the blog up and running.