Getting started with the Engine API

Estimated reading time: 17 minutes

To try out the Docker Engine API in development, you first need to install Docker.

Next, you need to install an SDK for the language you are using. There are official ones available for Python and Go, and a number of community maintained libraries for other languages. Head to the SDKs page to find and install them.

Running a container

The most basic thing you can do with Docker is running a container. On the command line, you would use the docker run command, but this is just as easy to do from your own apps too.

This is the equivalent of doing docker run alpine echo hello world:

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

import (
	"io"
	"os"

	"github.com/docker/engine-api/client"
	"github.com/docker/engine-api/types"
	"github.com/docker/engine-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, "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

You can also run containers in the background, the equivalent of docker run -d bfirsh/reticulate-splines:

Python
Go
curl
import docker
client = docker.from_env()
container = client.containers.run("bfirsh/reticulate-splines", detach=True)
print container.id
package main

import (
	"fmt"
	"io"
	"os"

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

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

	imageName := "bfirsh/reticulate-splines"

	out, err := cli.ImagePull(ctx, imageName, types.ImagePullOptions{})
	if err != nil {
		panic(err)
	}
	io.Copy(os.Stdout, out)

	resp, err := cli.ContainerCreate(ctx, &container.Config{
		Image: imageName,
	}, nil, nil, "")
	if err != nil {
		panic(err)
	}

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

	fmt.Println(resp.ID)
}
$ curl --unix-socket /var/run/docker.sock -H "Content-Type: application/json" \
  -d '{"Image": "bfirsh/reticulate-splines"}' \
  -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

Listing and managing containers

Like docker ps, we can use the API to list containers that are running:

Python
Go
curl
import docker
client = docker.from_env()
for container in client.containers.list():
  print container.id
package main

import (
	"context"
	"fmt"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
)

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

	containers, err := cli.ContainerList(context.Background(), types.ContainerListOptions{})
	if err != nil {
		panic(err)
	}

	for _, container := range containers {
		fmt.Println(container.ID)
	}
}
$ curl --unix-socket /var/run/docker.sock http:/v1.24/containers/json
[{
  "Id":"ae63e8b89a26f01f6b4b2c9a7817c31a1b6196acf560f66586fbc8809ffcd772",
  "Names":["/tender_wing"],
  "Image":"bfirsh/reticulate-splines",
  ...
}]

Now we know what containers exist, we can perform operations on them. For example, we can stop all running containers:

Python
Go
curl
import docker
client = docker.from_env()
for container in client.containers.list():
  container.stop()
package main

import (
	"context"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
)

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

	containers, err := cli.ContainerList(ctx, types.ContainerListOptions{})
	if err != nil {
		panic(err)
	}

	for _, container := range containers {
		if err := cli.ContainerStop(ctx, container.ID, nil); err != nil {
			panic(err)
		}
	}
}
$ curl --unix-socket /var/run/docker.sock http:/v1.24/containers/json
[{
  "Id":"ae63e8b89a26f01f6b4b2c9a7817c31a1b6196acf560f66586fbc8809ffcd772",
  "Names":["/tender_wing"],
  "Image":"bfirsh/reticulate-splines",
  ...
}]

$ curl --unix-socket /var/run/docker.sock \
  -X POST http:/v1.24/containers/ae63e8b89a26/stop

We can also perform actions on individual containers. For example, to print the logs of a container given its ID:

Python
Go
curl
import docker
client = docker.from_env()
container = client.containers.get('f1064a8a4c82')
print container.logs()
package main

import (
	"context"
	"io"
	"os"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
)

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

	options := types.ContainerLogsOptions{ShowStdout: true}
	out, err := cli.ContainerLogs(ctx, "f1064a8a4c82", options)
	if err != nil {
		panic(err)
	}

	io.Copy(os.Stdout, out)
}
$ curl --unix-socket /var/run/docker.sock "http:/v1.24/containers/ca5f55cdb/logs?stdout=1"
Reticulating spline 1...
Reticulating spline 2...
Reticulating spline 3...
Reticulating spline 4...
Reticulating spline 5...

Managing images

Images are the basis of containers, and can be managed in a similar way. You can list the images on your Engine, similar to docker images:

Python
Go
curl
import docker
client = docker.from_env()
for image in client.images.list():
  print image.id
package main

import (
	"context"
	"fmt"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/client"
)

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

	images, err := cli.ImageList(context.Background(), types.ImageListOptions{})
	if err != nil {
		panic(err)
	}

	for _, image := range images {
		fmt.Println(image.ID)
	}
}
$ curl --unix-socket /var/run/docker.sock http:/v1.24/images/json
[{
  "Id":"sha256:31d9a31e1dd803470c5a151b8919ef1988ac3efd44281ac59d43ad623f275dcd",
  "ParentId":"sha256:ee4603260daafe1a8c2f3b78fd760922918ab2441cbb2853ed5c439e59c52f96",
  ...
}]

You can pull images, like docker pull:

Python
Go
curl
import docker
client = docker.from_env()
image = client.images.pull("alpine")
print image.id
package main

import (
	"io"
	"os"

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

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

	out, err := cli.ImagePull(ctx, "alpine", types.ImagePullOptions{})
	if err != nil {
		panic(err)
	}

	io.Copy(os.Stdout, out)
}
$ curl --unix-socket /var/run/docker.sock \
  -X POST "http:/v1.24/images/create?fromImage=alpine"
{"status":"Pulling from library/alpine","id":"3.1"}
{"status":"Pulling fs layer","progressDetail":{},"id":"8f13703509f7"}
{"status":"Downloading","progressDetail":{"current":32768,"total":2244027},"progress":"[\u003e                                                  ] 32.77 kB/2.244 MB","id":"8f13703509f7"}
...

And commit containers to create images from their contents:

Python
Go
curl
import docker
client = docker.from_env()
container = client.run("alpine", ["touch", "/helloworld"], detached=True)
container.wait()
image = container.commit("helloworld")
print image.id
package main

import (
	"fmt"

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

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

	createResp, err := cli.ContainerCreate(ctx, &container.Config{
		Image: "alpine",
		Cmd:   []string{"touch", "/helloworld"},
	}, nil, nil, "")
	if err != nil {
		panic(err)
	}

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

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

	commitResp, err := cli.ContainerCommit(ctx, createResp.ID, types.ContainerCommitOptions{Reference: "helloworld"})
	if err != nil {
		panic(err)
	}

	fmt.Println(commitResp.ID)
}
$ docker run -d alpine touch /helloworld
0888269a9d584f0fa8fc96b3c0d8d57969ceea3a64acf47cd34eebb4744dbc52
$ curl --unix-socket /var/run/docker.sock\
  -X POST "http:/v1.24/commit?container=0888269a9d&repo=helloworld"
{"Id":"sha256:6c86a5cd4b87f2771648ce619e319f3e508394b5bfc2cdbd2d60f59d52acda6c"}

Next steps

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