Docker in development: Episode 3

In the last issue, we explained how to containerize Ruby on Rails applications. In this issue we'll explore how to perform everyday tasks in containers.

Run Rake tasks and Rails commands

Running Rake tasks is easy. After you build the image, you can use docker-compose to run commands in it. For example, if you want to view your application's routes:

$ docker-compose run web rails routes

Similarly, if you want to create a database, migrate and populate data:

$ docker-compose run web rails db:create db:migrate db:seed

If you want to run the test suite, you must create a test database:

$ docker-compose run web rails db:create db:migrate RAILS_ENV=test

Then run the test suite (assuming rake runs rake test by default):

$ docker-compose run web rake

Tip: Create custom scripts/aliases

I run docker-compose run web rails ... hundreds of times a day, and to make things easier I put this script inside my $PATH:

#!/bin/bash
docker-compose run web rails "$@"

Please note that this script assumes that your docker-compose.yml file has a web service. If not, it won't work.

Perform other tasks

So far all the commands are very simple and straightforward, you just need to run them in the web service. So what do you do with some of the more difficult tasks like loading a pre-existing database into a container's database? This was one of the tasks that took me a little longer to figure out.

In PostgreSQL, there are two ways to do this, depending on the format of the dump file. In the past, we had to deal with --format=c dumps and regular dumps.

Suppose you have a latest.dump file containing a PostgreSQL dump in c format, and you want to load it into a (running) container, first you have to find out the container ID. You can do this by running the following command:

$ docker container ls

or

$ docker ps

Once you have the container ID (in this example, we will use 80f8041db4b4), you can run the following command to restore the dump in the container:

$ docker exec -i 80f8041db4b4 pg_restore -d app_development -U postgres

If you have a regular dump (e.g. latest.sql), you can restore it using:

$ docker exec -i 80f8041db4b4 psql -d app_development -U postgres

If you are using docker-compose, things get easier:

$ docker-compose exec -T db pg_restore -d app_development -U postgres

Everything is containerized!

I use Elastic Beanstalk a lot. I usually install it using Homebrew, but it installs a lot of its own dependencies such as Python, SQLite, etc. I don't want all of this on my system, especially since I always have issues with the Python version. Instead, I containerize it: docker-awsebcli.

Stay tuned for the next issue!

The above is the detailed content of Docker in development: Episode 3. For more information, please follow other related articles on the PHP Chinese website!