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The Dockerfile should use the same Gemfile.lock as the app, to make sure the container gets the expected versions of gems installed. Aside from wanting that in principle, without it you can get mysterious gem dependency errors. Here's the scenario: 1. Suppose `Gemfile` includes `gem "some-active-gem", "~> 1.0" 2. When developing the app, you run `bundle install`, which installs the latest version--let's say, 1.0.1-and records it in `Gemfile.lock` 3. Suppose the developers of `some-active-gem` then release v1.0.2 4. Now build the container: docker runs `bundle install`, which installs v1.0.2 and records it in `Gemfile.lock` and then "ADD"s the app worktree, which replaces the `Gemfile.lock` with the one from the worktree that lists v1.0.1. 5. Immediately run your app and it fails with the error `Could not find some-active-gem-1.0.1 in any of the sources` which is a bit befuddling since you just saw it run bundle install so you expect all gem dependencies to be resolved properly. Signed-off-by: ronen barzel <ronen@barzel.org>
Docker Compose
(Previously known as Fig)
Compose is a tool for defining and running multi-container applications with Docker. With Compose, you define a multi-container application in a single file, then spin your application up in a single command which does everything that needs to be done to get it running.
Compose is great for development environments, staging servers, and CI. We don't recommend that you use it in production yet.
Using Compose is basically a three-step process.
- Define your app's environment with a
Dockerfileso it can be reproduced anywhere. - Define the services that make up your app in
docker-compose.ymlso they can be run together in an isolated environment: - Lastly, run
docker-compose upand Compose will start and run your entire app.
A docker-compose.yml looks like this:
web:
build: .
ports:
- "5000:5000"
volumes:
- .:/code
links:
- redis
redis:
image: redis
Compose has commands for managing the whole lifecycle of your application:
- Start, stop and rebuild services
- View the status of running services
- Stream the log output of running services
- Run a one-off command on a service
Installation and documentation
- Full documentation is available on Docker's website.
- If you have any questions, you can talk in real-time with other developers in the #docker-compose IRC channel on Freenode. Click here to join using IRCCloud.
Contributing
Want to help build Compose? Check out our contributing documentation.
Releasing
Releases are built by maintainers, following an outline of the release process.