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Docker Stacks and Distributed Application Bundles

Docker Stacks and Distributed Application Bundles

Overview

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.

From docker-compose :

$ 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

Managing stacks

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: version and services . The version used by Docker 1.12 tools is 0.1 .

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) string
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 []string
Command to run in service containers.
Args []string
Arguments passed to the service containers.
Env []string
Environment variables.
Labels map[string]string
Labels used for setting meta data on services.
Ports []Port
Service ports (composed of Port ( int ) and Protocol ( 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.
WorkingDir string
Working directory inside the service containers.
User string
Username or UID (format: <name|uid>[:<group|gid>] ).
Networks []string
Networks that the service containers should be connected to. An entity deploying a bundle should create networks as needed.

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