[PYTHON] Deploy Flask app on heroku (bitterly)

Deploy Flask app on heroku (bitterly)

It's quite difficult.

Error encountered in $ heroku logs --tail error code=H10 desc="App crashed" error code=h14 desc="no web processes running" Such. Even if each is treated with Stackoverflow etc., it will not be solved. However, it worked well in the following way.

Create a Python virtual environment

$ virtualenv flaskapp
$ cd flaskapp

Activate a virtual environment

$ source bin/activate

It looks like this.

$ (flaskapp) $

Here you can install various things with pip without affecting the machine environment.

For example

$ (flaskapp) $ pip install requests
$ (flaskapp) $ pip install Flask

Toka Toka.

Here, gunicorn and Flask are installed.

$ (flaskapp) $ pip3 install Flask gunicorn

[Gunicorn reference]: Gunicorn is a WSGI (Web Server Gateway Interface) HTTP Server of python and is a derivative of Unicorn of Ruby. Gunicorn is a lightweight server with a very simple implementation compared to various frameworks. Reference: https://qiita.com/arata-honda/items/09e1c350b1bd8a186e9c [How to use] Install gunicorn with pip install gunicorn, Start with gunicorn hello: app.

Preparing for Heroku

Assuming you've signed in on Heroku

Heroku CLI installation

$ (flaskapp) $ wget -qO- https://cli-assets.heroku.com/install-ubuntu.sh | sh

Log in to Heroku

$ (flaskapp) $ heroku login

Preparation file

• Procfile

$ echo "web: gunicorn app:app --log-file -" > Procfile

• requirements.txt

$ (flaskapp) $ pip3 freeze > requirements.txt

Click==7.0
Flask==1.1.1
gunicorn==20.0.4
itsdangerous==1.1.0
Jinja2==2.10.3
MarkupSafe==1.1.1
Werkzeug==0.16.0

--runtime.txt (optional)

$ (flaskapp) $ python -V | sed -n "s/Python /python-/p" > runtime.txt

• app.py

from flask import Flask
import os

app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello World!'


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=int(os.environ.get("PORT", 5000)))

Miso is not just app.run () here.

At this point, check if it works locally.

$ (flaskapp) $ python app.py
 * Serving Flask app "app" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)

$ curl http://127.0.0.1:5000
Hello World!

Deploy to heroku

$ (flaskapp) $ git init
$ (flaskapp) $ echo "*.DS_Store" > .gitignore
$ (flaskapp) $ git add .
$ (flaskapp) $ git commit -m 'first commit'
$ (flaskapp) $ heroku create
$ (flaskapp) $ git push heroku master

Operation check

Click the Open app button at the top right of the Heroku console screen

Another screen opened and Hello World was displayed safely.

Postscript

If you want to add a folder to Heroku

Even if I add a static folder that is often used in Flask to the app and deploy it on Heroku, it cannot be created on heroku. The reason is that git ignores empty folders. If you put the files in the static folder and then deploy it, a static folder will be created.

Reference: [Complete version] Procedure for deploying API created with Flask to Heroku (Note) Reference: [Error: No such file or directory:'/ app / {myappname} / static'”](https://stackoverflow.com/questions/19323513/heroku-django-oserror-no-such-file-or- directory-app-myappname-static)