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Published on 25 Jul 2022 2 min read

Optimizing Docker Containers

docker containers are relatively easy to get up and going, but can often be heavily optimized.

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As I’ve been building and shipping more and more docker images, I’ve realized that while it’s easy to get up and going, it can require quite a bit of work to get a “good” docker container setup.

Things you can do for a better docker container can include:

A starting point…

To make this a bit easier to discuss, we’re going to start with a very basic dockerfile example that is good enough to get you up and going but has lots of room for improvement.

FROM ubuntu:latest

# install os dependencies
RUN apt-get update && apt-get install
RUN apt-get python3 python3-dev python3-pip

# mount application code
COPY my-app my-app

# install app dependencies
RUN pip3 install -r requirements.txt

# run the application
CMD ["python3", "-m", "my-app:start_app()"]

okay, so what are the pain points with the approach above?

  1. A re-build is required whenever code changes are made
  2. Builds take ~3-5 minutes, docker’s caching layers are working against us.
  3. the image is pretty big (~450MB)

Experiment with different base images

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Limit access by running the app as a non-root user

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Multistage builds to save build time

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Use docker-compose as a default

Instead of having to remember the long and sometimes complicated docker run commands you’d have to run in the terminal, you can just use a docker-compose.yml file to store your config.

This also makes it really easy to spin up “accompanying” containers for dev/testing (e.g. a PostgreSQL DB, Redis Cache, etc.)

Containers for production and development

This is mostly a developer experience improvement, but it can actually improve your deploy experience, especially if you heavily use volumes for development.