Docker Engine API and SDKs

Estimated reading time: 4 minutes

The Engine API is the API served by Docker Engine. It allows you to control every aspect of Docker from within your own applications, build tools to manage and monitor applications running on Docker, and even use it to build apps on Docker itself.

It is the API the Docker client uses to communicate with the Engine, so everything the Docker client can do can be done with the API. For example:

  • Running and managing containers
  • Managing Swarm nodes and services
  • Reading logs and metrics
  • Creating and managing Swarms
  • Pulling and managing images
  • Managing networks and volumes

The API can be accessed with any HTTP client, but we also provide Python and Go SDKs.

Versioned API

The version of the API you should use depends upon the version of your Docker daemon. A new version of the API is released when new features are added. The Docker API is backward-compatible, so you do not need to update code that uses the API unless you need to take advantage of new features.

To see the highest version of the API your Docker daemon and client support, use docker version:

$ docker version

Client:
 Version:      17.04.0-ce
 API version:  1.28
 Go version:   go1.7.5
 Git commit:   4845c56
 Built:        Wed Apr  5 06:06:36 2017
 OS/Arch:      darwin/amd64

Server:
 Version:      17.04.0-ce
 API version:  1.28 (minimum version 1.12)
 Go version:   go1.7.5
 Git commit:   4845c56
 Built:        Tue Apr  4 00:37:25 2017
 OS/Arch:      linux/amd64
 Experimental: true

API example

As an example, the docker run command can be easily implemented in various programming languages and by hitting the API directly with curl:

  import docker
  client = docker.from_env()
  print client.containers.run("alpine", ["echo", "hello", "world"])
  
  package main

  import (
  	"io"
  	"os"

  	"github.com/moby/moby/client"
  	"github.com/moby/moby/api/types"
  	"github.com/moby/moby/api/types/container"
  	"golang.org/x/net/context"
  )

  func main() {
  	ctx := context.Background()
  	cli, err := client.NewEnvClient()
  	if err != nil {
  		panic(err)
  	}

  	_, err = cli.ImagePull(ctx, "docker.io/library/alpine", types.ImagePullOptions{})
  	if err != nil {
  		panic(err)
  	}

  	resp, err := cli.ContainerCreate(ctx, &container.Config{
  		Image: "alpine",
  		Cmd:   []string{"echo", "hello world"},
  	}, nil, nil, "")
  	if err != nil {
  		panic(err)
  	}

  	if err := cli.ContainerStart(ctx, resp.ID, types.ContainerStartOptions{}); err != nil {
  		panic(err)
  	}

  	if _, err = cli.ContainerWait(ctx, resp.ID); err != nil {
  		panic(err)
  	}

  	out, err := cli.ContainerLogs(ctx, resp.ID, types.ContainerLogsOptions{ShowStdout: true})
  	if err != nil {
  		panic(err)
  	}

  	io.Copy(os.Stdout, out)
  }
  
  $ curl --unix-socket /var/run/docker.sock -H "Content-Type: application/json" \
    -d '{"Image": "alpine", "Cmd": ["echo", "hello world"]}' \
    -X POST http:/v1.24/containers/create
  {"Id":"1c6594faf5","Warnings":null}

  $ curl --unix-socket /var/run/docker.sock -X POST http:/v1.24/containers/1c6594faf5/start

  $ curl --unix-socket /var/run/docker.sock -X POST http:/v1.24/containers/1c6594faf5/wait
  {"StatusCode":0}

  $ curl --unix-socket /var/run/docker.sock "http:/v1.24/containers/1c6594faf5/logs?stdout=1"
  hello world
  

To learn more, take a look at the getting started guide