Test-Driven Development with Python, 3rd Edition

Chapter 23. Debugging and Testing Server Issues

Popping a few layers off the stack of things we’re working on: we have nice wait-for helpers; what were we using them for? Oh yes, waiting to be logged in. And why was that? Ah yes, we had just built a way of pre-authenticating a user. Let’s see how that works against Docker and our staging server.

The Proof Is in the Pudding: Using Docker to Catch Final Bugs

Remember the deployment checklist from Chapter 18? Let’s see if it can’t come in handy today!

First, we rebuild and start our Docker container locally, on port 8888:

$ docker build -t superlists . && docker run \
    -p 8888:8888 \
    --mount type=bind,source="$PWD/container.db.sqlite3",target=/home/nonroot/db.sqlite3 \
    -e DJANGO_SECRET_KEY=sekrit \
    -e DJANGO_ALLOWED_HOST=localhost \
    -e DJANGO_DB_PATH=/home/nonroot/db.sqlite3 \
    -it superlists
[...]
 => => naming to docker.io/library/superlists [...]
[2025-01-27 22:37:02 +0000] [7] [INFO] Starting gunicorn 22.0.0
[2025-01-27 22:37:02 +0000] [7] [INFO] Listening at: http://0.0.0.0:8888 (7)
[2025-01-27 22:37:02 +0000] [7] [INFO] Using worker: sync
[2025-01-27 22:37:02 +0000] [8] [INFO] Booting worker with pid: 8

Note

If you see an error saying bind source path does not exist, you’ve lost your container database somehow. Create a new one with touch container.db.sqlite3.

Now let’s make sure our container database is fully up to date, by running migrate inside the container:

$ docker exec $(docker ps --filter=ancestor=superlists -q) python ...