Behavior-Driven Docker Development

This repository demonstrates how to use cucumber and behavior-driven development to orchestrate docker containers into a running 3-tiered application. It also can be used to quickly get a rails development environment running for a specific project.

Once you have all the pre-requisites installed, starting up a rails app is as simple as

$ docker-compose up -d

or

$ vagrant up --provision

And then you can visit http://localhost:8080 or http://localhost:3000 on your host machine to access the website.

But the real power of this setup is that we can develop new docker containers in a test-driven manner.

Pre-Requisites - Docker & Docker-Compose

Running Docker natively

This is the preferred approach, and supports Linux, Mac, and Windows machines. Install Docker and Docker-Compose.

Note on Vagrant

Previous versions supported using a docker-enabled virtual machine through Vagrant, but now that Docker runs on Mac and Windows, it's no longer necessary and has been removed.

Test Dependencies

In addition to installing docker and docker-compose, you'll need to have Cucumber installed in order to run the tests.

$ sudo apt-get install cucumber

Or,

• install ruby (e.g. via rvm or a system package)

• install cucumber

    $ gem install cucumber
  

Running the Tests

The tests ensure that the docker-compose cluster is running, so running them is as simple as running cucumber. You can also just run a specific test:

$ cucumber features/web.feature

If this is your first time running this, then grab a cup of coffee and enjoy a nice 10-15 minute wait, as the base docker images are downloaded, and then custom images are built and run. Subsequent executions will be much faster.

Starting the cluster

Running the tests also accomplishes this, but if you're too lazy to run the tests:

$ docker-compose run -d

When you make a change and want to rebuild a docker container

Again, running the tests accomplishes this, but if you want to do it manually:

$ docker-compose build

Using a rails-enabled dev environment

We've set up the dev service to also serve as a development environment, where you can issue commands like rails g scaffold. Since the files in this environment are the same files that you have locally, you can edit in your native environment, and use this environment for doing things like running tests, generating files, testing out dependencies, etc.

$ docker-compose run dev

Viewing Logs

This is a really nice feature of docker-compose, providing a combined output from all the running services.

$ docker-compose logs -f

This will show logs as they come in. Use Ctrl+C to quit.

Issues / Improvements

• bash: cannot set terminal process group (-1): Inappropriate ioctl for device
  • currently ignoring this message
• adding gems to the rails Gemfile is currently convoluted
  1. docker-compose run dev
  2. add the gem to Gemfile
  3. bundle install
  4. copy the new Gemfile and Gemfile.lock to dockerfiles/rails/
  5. re-build the rails container via docker-compose up -d or running cucumber
• the android tests take a long time downloading the gradle dependencies each time

Troubleshooting

• Couldn't connect to Docker daemon at http+unix://var/run/docker.sock - is it running?
  • Either add your user to the docker group (preferred), or use sudo docker-compose and sudo cucumber for the commands.
• vagrant up hangs for me
  • Try launching the virtual machine via VirtualBox directly to see if there are any errors.
• I'm on a 32-bit system but the virtualbox/docker images are 64-bit
  • We tried getting this to work with a 32-bit vagrant image, but ran into exec format error issues. A 32-bit fork of this project would be nice.
• I see a bunch of errors in the output saying stdin: is not a tty
  • These can safely be ignored, but if you can resolve the issue, please submit a pull request
• I get failures when I run cucumber, but when I run the failing commands manually, they pass.
  • This may be due to the tests running before the server is fully started. Currently, there's a hack in docker-compose_steps.rb to just sleep for 10 seconds after running docker-compose up, but this may not be suitable for all environments.

Thanks

• Thanks to the great work being done on Docker and Docker-Compose!