Nicolas De Loof
5bc5b864fc
Providers opt into image distribution by declaring a pull block in their metadata — the presence of the command block is the declaration of support, generalizing the stop precedent. During its pull command a provider can request the service image from the local daemon with a get-image message (optionally platform-narrowed); compose answers on stdin with one image-stream JSON line then the tar as HTTP/1.1 chunked data (RFC 9112): length-prefixed blocks need no in-band delimiter in binary data, the zero-length chunk marks a COMPLETE transfer, and any stock chunked reader consumes it. There is deliberately no trailer nor final CRLF after the zero chunk — a stock reader stops there without consuming further bytes, so the next stdin answer starts clean for a provider requesting several images. An export failure is announced in-band through the error field so the provider is never left waiting; a failure after the announce closes the answer channel so the truncation is observable as EOF mid-chunk instead of a stream nobody will finish. The stream is exclusive on stdin for its whole duration — the framing invariant behind the lock. get-image is scoped to the pull command: emitted during up, down or stop it is a protocol error rather than served, so an image export can never stall another lifecycle command. Message dispatch moves out of executePlugin into handlePluginMessage, which also keeps the function under the complexity threshold. Signed-off-by: Nicolas De Loof <[email protected]>
Table of Contents
Docker Compose
Docker Compose is a tool for running multi-container applications on Docker
defined using the Compose file format.
A Compose file is used to define how one or more containers that make up
your application are configured.
Once you have a Compose file, you can create and start your application with a
single command: docker compose up.
Note
: About Docker Swarm Docker Swarm used to rely on the legacy compose file format but did not adopt the compose specification so is missing some of the recent enhancements in the compose syntax. After acquisition by Mirantis swarm isn't maintained by Docker Inc, and as such some Docker Compose features aren't accessible to swarm users.
Where to get Docker Compose
Windows and macOS
Docker Compose is included in Docker Desktop for Windows and macOS.
Linux
You can download Docker Compose binaries from the release page on this repository.
Rename the relevant binary for your OS to docker-compose and copy it to $HOME/.docker/cli-plugins
Or copy it into one of these folders to install it system-wide:
/usr/local/lib/docker/cli-pluginsOR/usr/local/libexec/docker/cli-plugins/usr/lib/docker/cli-pluginsOR/usr/libexec/docker/cli-plugins
(might require making the downloaded file executable with chmod +x)
Quick Start
Using Docker Compose is 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
compose.yamlso they can be run together in an isolated environment. - Lastly, run
docker compose upand Compose will start and run your entire app.
A Compose file looks like this:
services:
web:
build: .
ports:
- "5000:5000"
volumes:
- .:/code
redis:
image: redis
Contributing
Want to help develop Docker Compose? Check out our contributing documentation.
If you find an issue, please report it on the issue tracker.
Legacy
The Python version of Compose is available under the v1 branch.