Corndel

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Deploying a flask app ​

Setting up Github ​

We should run

bash
git init

and create a .gitignore.

Details

A reasonable .gitignore for this project might look like this:

# Local
venv/
.env
.env.*
dev.sqlite

# Byte-compiled / optimized / DLL files
__pycache__/

# Unit test / coverage reports
.pytest_cache/

# Flask stuff:
instance/
.webassets-cache

If we create an empty repo on Github, we can link it to the local like this:

bash
# Stage all changes
git add .

# Commit all changes
git commit -am "initial commit"

# Add the remote
git remote add origin <your-repo-url>

# Push your code
git push -u origin main

TIP

The -u origin main part links the local main branch to the remote main branch, and means that in the future we only need to do git push.

Deploying on Render ​

Render is a service which allows us to deploy an api for free.

We can get started by signing up and selecting to create a new web service.

We can determine the build command, which is usually something like

bash
pip install -r requirements.txt

We can also specify the command to start the app. The actual command will vary depending on how your app is set up, could be something like

bash
gunicorn -e MODE=production -w 4 -b 0.0.0.0:$PORT 'src.app:create_app()'

  • -e MODE=production sets the environment variable MODE to "production"

  • -w 4 sets up 4 workers, to allow concurrent request handling

  • -b 0.0.0.0:$PORT binds the app to a specific host and port, where $PORT is an environment variable provided by Render

INFO

The app.run() method starts a development server. It is not intended for high traffic deployments. Gunicorn is a development server and can be installed with pip install gunicorn. Be sure the add this to requirements.txt.

Environment variables ​

We can specify a list of environment variables. This allows us to choose a different configuration for production compared with local development.

bash
SECRET_KEY=bac954ba70aec51f59966de92702e887f8801c374de2c369e24133b0cb9d3380
DB_URL=postgresql://postgres.imivjbohxrpueurbqdho:y8QsnKBXSvjCG2DA@aws-0-eu-west-2.pooler.supabase.com:6543/postgres

WARNING

Your database url contains the database password. It is structured like this:

postgresql://[user:password]@[host][:port][/dbname]

It is extremely sensitive and should not be shared or stored anywhere else.

TIP

The production database is hosted on Supabase, which is a good choice if you would like to experiment for free with a hosted database.

Visiting the site ​

When we push to the main branch on Github, Render will automatically rebuild and redploy the app, and we can view at at the url, e.g. https://corndel-todo.onrender.com.