Demo Docker Stack

In this lesson, we’ll deploy the Example Voting App using Docker Stacks on a Swarm cluster. We start by upgrading our Compose file to version 3, deploy it as a stack, verify running services, and then scale the voting service.

1. Prepare the Docker Compose File (Version 3)

Below is the upgraded Compose file in version 3 format. Save this as docker-stack.yml on your Swarm manager:

version: '3'
services:
  redis:
    image: redis
  db:
    image: postgres:9.4
  vote:
    image: dockersamples/examplevotingapp_vote
    ports:
      - "5000:80"
  worker:
    image: dockersamples/examplevotingapp_worker
  result:
    image: dockersamples/examplevotingapp_result
    ports:
      - "5001:80"

The dockersamples images are available on Docker Hub.

Make sure Docker Swarm is initialized on your manager node:

docker swarm init

2. Deploy the Stack

SSH into your Swarm manager and create a project directory:
mkdir ~/voting-app-stack && cd ~/voting-app-stack
Place the docker-stack.yml file in this directory.

Deploy the stack:

docker stack deploy voting-app-stack --compose-file docker-stack.yml

You should see output similar to:

Compose

Creating network voting-app-stack_default
Creating service voting-app-stack_redis
Creating service voting-app-stack_db
Creating service voting-app-stack_vote
Creating service voting-app-stack_worker
Creating service voting-app-stack_result

Verify all services are up:

docker service ls

Service Name	Replicas	Image
voting-app-stack_redis	1/1	redis:latest
voting-app-stack_db	1/1	postgres:9.4
voting-app-stack_vote	1/1	dockersamples/examplevotingapp_vote:latest
voting-app-stack_worker	0/1	dockersamples/examplevotingapp_worker:latest
voting-app-stack_result	1/1	dockersamples/examplevotingapp_result:latest

3. Inspect Running Tasks

On any manager or worker node, list the active containers to ensure tasks are distributed:

docker ps

Example output:

CONTAINER ID  IMAGE                                           NAMES
3940e228ce02  dockersamples/examplevotingapp_result:latest    voting-app-stack_result.1.abcde
9348d1d3d7f5  postgres:9.4                                    voting-app-stack_db.1.fghij

4. Access the Voting Application

Open a browser and navigate to:

Voting interface: http://<manager-ip>:5000
Results dashboard: http://<manager-ip>:5001

The image shows a web page titled "Cats vs Dogs!" with options to vote for either "CATS" or "DOGS," and the "CATS" option is selected.

5. Scale the Voting Service

To handle higher traffic, update docker-stack.yml by adding the deploy.replicas setting under the vote service:

services:
  vote:
    image: dockersamples/examplevotingapp_vote
    ports:
      - "5000:80"
    deploy:
      replicas: 2

Redeploy the updated stack:

docker stack deploy voting-app-stack --compose-file docker-stack.yml

Confirm that the voting service now has two replicas:

docker service ls

Service Name	Replicas	Image
voting-app-stack_vote	2/2	dockersamples/examplevotingapp_vote:latest
voting-app-stack_db	1/1	postgres:9.4
voting-app-stack_redis	1/1	redis:latest
voting-app-stack_result	1/1	dockersamples/examplevotingapp_result:latest
voting-app-stack_worker	1/1	dockersamples/examplevotingapp_worker:latest

Inspect each task:

docker service ps voting-app-stack_vote

Links and References

This demonstrates how to deploy, verify, and scale services using Docker Stacks in a Swarm cluster.

Introduction

Docker Engine

Docker Image Management

Docker Engine - Security

Docker Engine - Networking

Docker Engine - Storage

Docker Compose

Docker Swarm

Kubernetes

Docker Engine Enterprise

Docker Trusted Registry

Disaster Recovery

1. Prepare the Docker Compose File (Version 3)

2. Deploy the Stack

3. Inspect Running Tasks

4. Access the Voting Application

5. Scale the Voting Service

Links and References

Watch Video

​1. Prepare the Docker Compose File (Version 3)

​2. Deploy the Stack

​3. Inspect Running Tasks

​4. Access the Voting Application

​5. Scale the Voting Service

​Links and References

Watch Video

1. Prepare the Docker Compose File (Version 3)

2. Deploy the Stack

3. Inspect Running Tasks

4. Access the Voting Application

5. Scale the Voting Service

Links and References