Docker Stacks and Distributed Application Bundles
Docker Stacks and Distributed Application Bundles are experimental features introduced in Docker 1.12 and Docker Compose 1.8, alongside the concept of swarm mode, and Nodes and Services in the Engine API.
A Dockerfile can be built into an image, and containers can be created from that image. Similarly, a docker-compose.yml can be built into a distributed application bundle , and stacks can be created from that bundle. In that sense, the bundle is a multi-services distributable image format.
As of Docker 1.12 and Compose 1.8, the features are experimental. Neither Docker Engine nor the Docker Registry support distribution of bundles.
Producing a bundle
The easiest way to produce a bundle is to generate it using
docker-compose from an existing
docker-compose.yml . Of course, that’s just one possible way to proceed, in the same way that
docker build isn’t the only way to produce a Docker image.
$ docker-compose bundle WARNING: Unsupported key 'network_mode' in services.nsqd - ignoring WARNING: Unsupported key 'links' in services.nsqd - ignoring WARNING: Unsupported key 'volumes' in services.nsqd - ignoring [...] Wrote bundle to vossibility-stack.dsb
Creating a stack from a bundle
A stack is created using the
docker deploy command:
# docker deploy --help Usage: docker deploy [OPTIONS] STACK Create and update a stack Options: -f, --bundle string Path to a bundle (Default: STACK.dsb) --help Print usage
Let’s deploy the stack created before:
# docker deploy vossibility-stack Loading bundle from vossibility-stack.dsb Creating service vossibility-stack_elasticsearch Creating service vossibility-stack_kibana Creating service vossibility-stack_logstash Creating service vossibility-stack_lookupd Creating service vossibility-stack_nsqd Creating service vossibility-stack_vossibility-collector
We can verify that services were correctly created:
# docker service ls ID NAME REPLICAS IMAGE COMMAND 29bv0vnlm903 vossibility-stack_lookupd 1 nsqio/nsq@sha256:eeba05599f31eba418e96e71e0984c3dc96963ceb66924dd37a47bf7ce18a662 /nsqlookupd 4awt47624qwh vossibility-stack_nsqd 1 nsqio/nsq@sha256:eeba05599f31eba418e96e71e0984c3dc96963ceb66924dd37a47bf7ce18a662 /nsqd --data-path=/data --lookupd-tcp-address=lookupd:4160 4tjx9biia6fs vossibility-stack_elasticsearch 1 elasticsearch@sha256:12ac7c6af55d001f71800b83ba91a04f716e58d82e748fa6e5a7359eed2301aa 7563uuzr9eys vossibility-stack_kibana 1 kibana@sha256:6995a2d25709a62694a937b8a529ff36da92ebee74bafd7bf00e6caf6db2eb03 9gc5m4met4he vossibility-stack_logstash 1 logstash@sha256:2dc8bddd1bb4a5a34e8ebaf73749f6413c101b2edef6617f2f7713926d2141fe logstash -f /etc/logstash/conf.d/logstash.conf axqh55ipl40h vossibility-stack_vossibility-collector 1 icecrime/vossibility-collector@sha256:f03f2977203ba6253988c18d04061c5ec7aab46bca9dfd89a9a1fa4500989fba --config /config/config.toml --debug
Tasks are managed using the
docker stack command:
# docker stack --help Usage: docker stack COMMAND Manage Docker stacks Options: --help Print usage Commands: config Print the stack configuration deploy Create and update a stack rm Remove the stack tasks List the tasks in the stack Run 'docker stack COMMAND --help' for more information on a command.
Bundle file format
Distributed application bundles are described in a JSON format. When bundles are persisted as files, the file extension is
.dab (Docker 1.12RC2 tools use
.dsb for the file extension—this will be updated in the next release client).
A bundle has two top-level fields:
services . The version used by Docker 1.12 tools is
services in the bundle are the services that comprise the app. They correspond to the new
Service object introduced in the 1.12 Docker Engine API.
A service has the following fields:
- Image (required)
- The image that the service will run. Docker images should be referenced with full content hash to fully specify the deployment artifact for the service. Example:
postgres@sha256:f76245b04ddbcebab5bb6c28e76947f49222c99fec4aadb0bb 1c24821a 9e83ef
- Command to run in service containers.
- Arguments passed to the service containers.
- Environment variables.
- Labels used for setting meta data on services.
- Service ports (composed of
string). A service description can only specify the container port to be exposed. These ports can be mapped on runtime hosts at the operator’s discretion.
- Working directory inside the service containers.
- Username or UID (format:
- Networks that the service containers should be connected to. An entity deploying a bundle should create networks as needed.