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Docker

aka how to retain your sanity

Killer docker commands

  • docker ps: like UNIX ps, shows running containers:
# show all running containers + what ports they expose
$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                              NAMES
19c1bd134143        postgres:12         "docker-entrypoint.s…"   4 hours ago         Up 4 hours          5432/tcp, 0.0.0.0:6544->6544/tcp   app_postgres_tests_1
  • docker stop {name} you can use the CONTAINER ID (or the first few characters), or NAMES to refer to it. You can list multiple containers and it'll kill them all. These all stop that container:
# these all kill the postgres container above
$ docker stop 19c1bd134143
$ docker stop 19c
$ docker stop app_postgres_tests_1

  • docker stop $(docker ps -q) kills all current containers (-q shows only the container id)

  • docker logs {name}: lets you inspect logs of a container, also add --follow to stream them to stdout. Useful if you start containers in daemon mode. E.g.

docker logs --follow app_postgres_tests_1

Useful docker-compose stuff

docker-compose up starts all containers in the docker-compose.yml in that folder

Options:

  • --build : you probably want to be using this most of the time if you're changing stuff that goes into containers, it'll recreate the container
  • -d: do it in "daemon" mode, in the background. This is also super useful if you want to run some containers in the background (e.g. the database) and monitor others in the foreground.
  • docker-compose up {container1} {container2} will only start container1 and container2
  • You can run multiple docker-composes in different screens and they'll be able to communicate. This is very useful e.g. if you want to have the postgres container up and see the executed SQL queries in one window, and the backend container in another window and recreate it frequently
  • --no-deps: don't bring up other containers that this depends on
  • --force-recreate: forces the container to be recreated, if something happened outside the "context" of the container and you need to recreate it
  • -f: specify a different docker-compose file, e.g. docker-compose -f docker-compose.test.yml up postgres_tests

Some common patterns

Run only the proxy, backend, and database

docker-compose up --build proxy backend

This will spin up the proxy, backend and postgres database (since the postgres container is a dependency of the backend). You can then do queries against the backend at localhost:8888 (which hits the proxy that redirects it to the backend, which will mutate the database).

Run the backend tests with postgres in background

Start postgres_tests in the background and run tests in foreground:

docker-compose -f docker-compose.test.yml up -d postgres_tests
docker-compose -f docker-compose.test.yml up --build --no-deps backend_tests