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Docker Setup

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Timothy Ko edited this page Apr 4, 2019 · 6 revisions

Docker Setup

We will be utilizing Docker to provide the same development environment across your team. This will eliminate aggravating environment troubleshooting in different Operating Systems. We will not be using Docker in production since deployment using Heroku is easier. The following dockerizes all the components including the flask app. I'd recommend you to just run postgres inside the docker container and run the flask app inside a python virtual environment using pipenv. I wrote about all of this in Step by step setup instructions.

Prereqs

  • Docker – if you are running Linux, install the Server version and install Docker-Compose. And that's it! For Mac, you will see a Docker icon on the top bar, indicating that docker is running.

Understanding Docker

Docker is a powerful tool that allows you to spin up containers(isolated and reproducible application environments), thus, allowing independence between applications and the infrastucture(ie your OS). For in-depth information, check out the Docker Docs

  • Docker Images, what you get when you docker-compose build. They are snapshots of your code at that certain time. This describes a container
  • Docker Containers are instances of images. You can see the containers you are running with docker ps
  • Docker Compose is a tool for running multi-container applications with Docker. In our case, we use it to spin up app and postgres containers.

Our Docker Configuration

We have two Docker Images:

  • app: Our Flask Application
  • postgres: Postgres Database
    Note: A docker volume will be created to persist the Postgres data. You may remove it by using docker volume prune. However, you must remove the container using it (app) with the command docker rm app.

Setup

Check if you have installed Docker and Docker-Compose(Installing Docker on Mac/Windows will automatically install Docker-Compose):

$ docker -v
Docker version 17.09.1-ce, build 19e2cf6
$ docker-compose -v
docker-compose version 1.17.1, build 6d101fb

Now build the Docker images(the flask app and postgres database) and setup the database:

$ docker-compose up -d

Check if your Docker Containers are running:

$ docker ps

Now go to http://localhost:5000 and you should see the app running! Since it is in development configurations, any changes in your code will appear in the container and will auto-reload just like it would normally.

Running and Stopping Docker Containers

To start your Postgres and your flask api:

$ docker-compose start

To stop them:

$ docker-compose stop

To view your logs for the api:

$ docker-compose logs app

If you need to rebuild your containers, delete the previous containers and rebuild

$ docker-compose rm -f
$ docker-compose up -d

NOTE: Be careful to not run multiple containers of the same image. Check with docker ps and use docker-compose stop to stop all the containers if you are running multiple containers and restart.

Docker and Databases

Any commands, such as python manage.py db migrate MUST be performed inside the app Docker Container. If you need to access the postgres CLI, you MUST be inside the postgres Docker Container.

Migrating the database

You must access the app container's bash. You will then see your app directory copied inside:

$ docker-compose exec app bash
# ls
Dockerfile  Procfile   __pycache__  config.py		docs	   postgres-data     runtime.txt  venv
LICENSE     README.md  api	    docker-compose.yml	manage.py  requirements.txt  tests	  wait-for-postgres.sh

Then initalize migration files and migrate

# python manage.py db init
# python manage.py db migrate
# python manage.py db upgrade
# exit

Accessing Postgres CLI

You must access the postgres container's bash.

$ docker-compose exec postgres bash

Then, you can psql inside and delete tables, databases, etc.

# su - postgres
$ psql

Wiping all Docker Containers and Starting all over again

If you've given up trying to troubleshoot whatever is going wrong in Docker, here's a way to start all over.

First, stop the postgres container that you are running. Then, delete the postgres container. I like to just use docker system prune to delete all unused containers. Afterwards, we need to delete the volume persisting all of the database data.

$ docker volume rm flask-app-db

If you are using docker-compose, then delete all your related Docker Images and Containers

$ docker-compose stop
$ docker-compose rm
$ docker rmi $(docker images)

Now follow the setup steps again

Common Docker commands

Stop the API and Postgres Containers

docker-compose stop

List all Containers:

$ docker ps

Stop all Containers:

$ docker stop $(docker ps -a)

Remove all images:

$ docker rmi $(docker images -q)

To get all images

$ docker images

Remove specific images:

$ docker rmi [IMAGE_ID]

Bash in a certain container, ie: api

$ docker-compose run api bash

You can also run bash if you have the container's id. To get a container's id, do docker ps

$ docker exec -it [CONTAINER_ID] /bin/bash

Or run a specific bash command, id: ls

$ docker exec -it [CONTAINER_ID] ls

Remove

  • all stopped containers
  • all volumes not used by at least one container
  • all networks not used by at least one container
  • all images without at least one container associated to them
$ docker system prune

Show all stopped Docker containers

$ docker ps -a | grep Exit

Basics

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