Docker
Docker¶
Docker containers avoid many problems and irritating snags related to conflicting versions of Python and libraries when setting up a development environment on your machine.
In the Dockerized environment, all the code runs in an isolated virtual environment, so there are no version conflicts. A Docker environment is similar to a virtual machine but more efficient regarding resources.
Docker containers standardise deployment environment, helping to prevent “Well It Works On My Machine”-type deployment difficulties.
Downloading and Installing Docker¶
Docker installation on Mac / Linux is straightforward.
Unfortunately, for Windows users, it's a bit more involved.
See this official tutorial from the Docker website. You must also install the Windows Subsystem for Linux (WSL).
It's completely worth it to save many hours of frustration and headaches!
Docker Example¶
See the docker-compose example in the RCPCH Audit Engine repository to see how this works in practice.
In this project, we reduce confusing development environment setup to one command, which you type inside the top-level directory:
s/docker-up
This is a small bash script which runs:
docker compose up
Through this, we ensure developers use the same hand-crafted development environment, which can update if required.
The only downside is that sometimes you need to remember your server is inside the Docker container and run commands outside the container, and then puzzle over why it's not working!
Docker and docker compose tips¶
docker compose vs docker-compose
After a recent update, it's docker compose (with a space, not a hyphen).
It used to be docker-compose for a long time; even some recent tutorials may have this wrong.
- To run a command in the context of a docker compose suite of containers, you type:
docker compose exec [CONTAINER_NAME] [COMMAND]
docker compose exec web python manage.py runserver
VSCode Docker GUI Extension
The VSCode Docker extension allows you to directly attach a shell to Docker containers and view logs.
This allows you to run terminal commands 'natively' within the container's context, meaning you no longer need to prepend docker compose exec [CONTAINER_NAME] before each command