---
description: How to deploy a stack to a swarm
keywords: guide, swarm mode, composefile, stack, compose, deploy
title: Deploy a stack to a swarm
---

When running Docker Engine in swarm mode, you can use `docker stack deploy` to
deploy a complete application stack to the swarm. The `deploy` command accepts
a stack description in the form of a [Compose file](../../compose/compose-file/compose-file-v3.md).

The `docker stack deploy` command supports any Compose file of version "3.0" or
above. If you have an older version, see the [upgrade guide](../../compose/compose-file/compose-versioning.md#upgrading).

To run through this tutorial, you need:

1.  A Docker Engine running in [swarm mode](swarm-mode.md).
    If you're not familiar with swarm mode, you might want to read
    [Swarm mode key concepts](key-concepts.md)
    and [How services work](how-swarm-mode-works/services.md).

    > **Note**
    >
    > If you're trying things out on a local development environment,
    > you can put your engine into swarm mode with `docker swarm init`.
    >
    > If you've already got a multi-node swarm running, keep in mind that all
    > `docker stack` and `docker service` commands must be run from a manager
    > node.

2.  A current version of [Docker Compose](../../compose/install.md).


## Set up a Docker registry

Because a swarm consists of multiple Docker Engines, a registry is required to
distribute images to all of them. You can use the
[Docker Hub](https://hub.docker.com) or maintain your own. Here's how to create
a throwaway registry, which you can discard afterward.

1.  Start the registry as a service on your swarm:

    ```console
    $ docker service create --name registry --publish published=5000,target=5000 registry:2
    ```

2.  Check its status with `docker service ls`:

    ```console
    $ docker service ls

    ID            NAME      REPLICAS  IMAGE                                                                               COMMAND
    l7791tpuwkco  registry  1/1       registry:2@sha256:1152291c7f93a4ea2ddc95e46d142c31e743b6dd70e194af9e6ebe530f782c17
    ```

    Once it reads `1/1` under `REPLICAS`, it's running. If it reads `0/1`, it's
    probably still pulling the image.

3.  Check that it's working with `curl`:

    ```console
    $ curl http://localhost:5000/v2/

    {}
    ```

## Create the example application

The app used in this guide is based on the hit counter app in the
[Get started with Docker Compose](../../compose/gettingstarted.md) guide. It consists
of a Python app which maintains a counter in a Redis instance and increments the
counter whenever you visit it.

1.  Create a directory for the project:

    ```console
    $ mkdir stackdemo
    $ cd stackdemo
    ```

2.  Create a file called `app.py` in the project directory and paste this in:

    ```python
    from flask import Flask
    from redis import Redis

    app = Flask(__name__)
    redis = Redis(host='redis', port=6379)

    @app.route('/')
    def hello():
        count = redis.incr('hits')
        return 'Hello World! I have been seen {} times.\n'.format(count)

    if __name__ == "__main__":
        app.run(host="0.0.0.0", port=8000, debug=True)
    ```

3.  Create a file called `requirements.txt` and paste these two lines in:

    ```none
    flask
    redis
    ```

4.  Create a file called `Dockerfile` and paste this in:

    ```dockerfile
    # syntax=docker/dockerfile:1
    FROM python:3.4-alpine
    ADD . /code
    WORKDIR /code
    RUN pip install -r requirements.txt
    CMD ["python", "app.py"]
    ```

5.  Create a file called `docker-compose.yml` and paste this in:

    ```none
    version: "{{ site.compose_file_v3 }}"

    services:
      web:
        image: 127.0.0.1:5000/stackdemo
        build: .
        ports:
          - "8000:8000"
      redis:
        image: redis:alpine
    ```

    The image for the web app is built using the Dockerfile defined
    above. It's also tagged with `127.0.0.1:5000` - the address of the registry
    created earlier. This is important when distributing the app to the
    swarm.


## Test the app with Compose

1.  Start the app with `docker-compose up`. This builds the web app image,
    pulls the Redis image if you don't already have it, and creates two
    containers.

    You see a warning about the Engine being in swarm mode. This is because
    Compose doesn't take advantage of swarm mode, and deploys everything to a
    single node. You can safely ignore this.

    ```none
    $ docker-compose up -d

    WARNING: The Docker Engine you're using is running in swarm mode.

    Compose does not use swarm mode to deploy services to multiple nodes in
    a swarm. All containers are scheduled on the current node.

    To deploy your application across the swarm, use `docker stack deploy`.

    Creating network "stackdemo_default" with the default driver
    Building web
    ...(build output)...
    Creating stackdemo_redis_1
    Creating stackdemo_web_1
    ```

2.  Check that the app is running with `docker-compose ps`:

    ```console
    $ docker-compose ps

          Name                     Command               State           Ports
    -----------------------------------------------------------------------------------
    stackdemo_redis_1   docker-entrypoint.sh redis ...   Up      6379/tcp
    stackdemo_web_1     python app.py                    Up      0.0.0.0:8000->8000/tcp
    ```

    You can test the app with `curl`:

    ```console
    $ curl http://localhost:8000
    Hello World! I have been seen 1 times.

    $ curl http://localhost:8000
    Hello World! I have been seen 2 times.

    $ curl http://localhost:8000
    Hello World! I have been seen 3 times.
    ```

3.  Bring the app down:

    ```console
    $ docker-compose down --volumes

    Stopping stackdemo_web_1 ... done
    Stopping stackdemo_redis_1 ... done
    Removing stackdemo_web_1 ... done
    Removing stackdemo_redis_1 ... done
    Removing network stackdemo_default
    ```


## Push the generated image to the registry

To distribute the web app's image across the swarm, it needs to be pushed to the
registry you set up earlier. With Compose, this is very simple:

```console
$ docker-compose push

Pushing web (127.0.0.1:5000/stackdemo:latest)...
The push refers to a repository [127.0.0.1:5000/stackdemo]
5b5a49501a76: Pushed
be44185ce609: Pushed
bd7330a79bcf: Pushed
c9fc143a069a: Pushed
011b303988d2: Pushed
latest: digest: sha256:a81840ebf5ac24b42c1c676cbda3b2cb144580ee347c07e1bc80e35e5ca76507 size: 1372
```

The stack is now ready to be deployed.


## Deploy the stack to the swarm

1.  Create the stack with `docker stack deploy`:

    ```console
    $ docker stack deploy --compose-file docker-compose.yml stackdemo

    Ignoring unsupported options: build

    Creating network stackdemo_default
    Creating service stackdemo_web
    Creating service stackdemo_redis
    ```

    The last argument is a name for the stack. Each network, volume and service
    name is prefixed with the stack name.

2.  Check that it's running with `docker stack services stackdemo`:

    ```console
    $ docker stack services stackdemo

    ID            NAME             MODE        REPLICAS  IMAGE
    orvjk2263y1p  stackdemo_redis  replicated  1/1       redis:3.2-alpine@sha256:f1ed3708f538b537eb9c2a7dd50dc90a706f7debd7e1196c9264edeea521a86d
    s1nf0xy8t1un  stackdemo_web    replicated  1/1       127.0.0.1:5000/stackdemo@sha256:adb070e0805d04ba2f92c724298370b7a4eb19860222120d43e0f6351ddbc26f
    ```

    Once it's running, you should see `1/1` under `REPLICAS` for both services.
    This might take some time if you have a multi-node swarm, as images need to
    be pulled.

    As before, you can test the app with `curl`:

    ```console
    $ curl http://localhost:8000
    Hello World! I have been seen 1 times.

    $ curl http://localhost:8000
    Hello World! I have been seen 2 times.

    $ curl http://localhost:8000
    Hello World! I have been seen 3 times.
    ```

    Thanks to Docker's built-in routing mesh, you can access any node in the
    swarm on port 8000 and get routed to the app:

    ```console
    $ curl http://address-of-other-node:8000
    Hello World! I have been seen 4 times.
    ```

3.  Bring the stack down with `docker stack rm`:

    ```console
    $ docker stack rm stackdemo

    Removing service stackdemo_web
    Removing service stackdemo_redis
    Removing network stackdemo_default
    ```

4.  Bring the registry down with `docker service rm`:

    ```console
    $ docker service rm registry
    ```

5.  If you're just testing things out on a local machine and want to bring your
    Docker Engine out of swarm mode, use `docker swarm leave`:

    ```console
    $ docker swarm leave --force

    Node left the swarm.
    ```
