> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Example Voting Application with Docker Compose

> Learn to orchestrate a multi-service voting application using Docker Compose, including Redis, PostgreSQL, a voting frontend, a worker processor, and a results dashboard.

In this step-by-step tutorial, you’ll learn how to orchestrate a multi-service voting application using Docker Compose. By the end, you’ll have a running stack that includes Redis, PostgreSQL, a voting frontend, a worker processor, and a results dashboard.

## Prerequisites

* Docker Engine installed (version ≥ 19.03)
* Basic familiarity with `docker` CLI
* A terminal/SSH session on Linux, macOS, or Windows WSL

## Step 1: Install Docker Compose

Docker Compose isn’t bundled with Docker Engine by default. Install it on Linux with:

```bash theme={null}
sudo curl -L "https://github.com/docker/compose/releases/download/1.16.1/docker-compose-$(uname -s)-$(uname -m)" \
  -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose
docker-compose --version
```

Expected output:

```bash theme={null}
docker-compose version 1.16.1, build 1719ceb
```

<Callout icon="lightbulb" color="#1CB2FE">
  Replace `1.16.1` with the latest stable release. See the [Compose releases on GitHub](https://github.com/docker/compose/releases) for details.
</Callout>

## Step 2: Clean Up Existing Containers

Before deploying, stop any previous demo containers:

```bash theme={null}
# List running containers
docker ps

# Stop containers by ID or prefix
docker stop 69 54 5b 2f 0b

# Verify all relevant containers are stopped
docker ps
```

<Callout icon="triangle-alert" color="#FF6B6B">
  Stopping containers will terminate running services. Ensure you don’t have unsaved data in those containers.
</Callout>

## Step 3: Define Services in docker-compose.yml

Create a file named `docker-compose.yml` with the following content. It leverages Compose file format version 3.

```yaml theme={null}
version: '3'
services:
  redis:
    image: redis

  db:
    image: postgres:9.4

  vote:
    image: voting-app
    ports:
      - "5000:80"
    depends_on:
      - redis

  worker:
    image: worker-app
    depends_on:
      - db
      - redis

  result:
    image: result-app
    ports:
      - "5001:80"
    depends_on:
      - db
```

### Service Overview

| Service | Image          | Ports   | Description                                   |
| ------- | -------------- | ------- | --------------------------------------------- |
| redis   | `redis`        | –       | In-memory queue for incoming votes            |
| db      | `postgres:9.4` | –       | Persistent storage for vote records           |
| vote    | `voting-app`   | 5000→80 | Frontend where users cast their vote          |
| worker  | `worker-app`   | –       | Processes queued votes into the PostgreSQL DB |
| result  | `result-app`   | 5001→80 | Displays aggregated vote results              |

<Callout icon="lightbulb" color="#1CB2FE">
  The `depends_on` key ensures containers start in the correct order, but it doesn’t wait for health checks. Consider adding healthchecks for production workloads.\
  See the [Compose file reference](https://docs.docker.com/compose/compose-file/compose-versioning/) for advanced options.
</Callout>

## Step 4: Deploy the Stack

From the directory containing `docker-compose.yml`, run:

```bash theme={null}
docker-compose up -d
```

This command will pull images, create a default network, and start all five containers. Container names are prefixed by your folder name (e.g., `root_redis_1`).

Verify everything is up:

```bash theme={null}
docker ps
```

You should see containers for Redis, PostgreSQL, vote, worker, and result.

## Step 5: Access the Application

* Voting interface: [http://localhost:5000](http://localhost:5000)
* Results dashboard: [http://localhost:5001](http://localhost:5001)

Cast a vote on the first page, then switch to the results page to see real-time counts.

<Frame>
  ![The image shows a webpage titled "Cats vs Dogs!" with two buttons labeled "CATS" and "DOGS," where "DOGS" is selected. It also mentions that you can change your vote and displays a container ID at the bottom.](https://kodekloud.com/kk-media/image/upload/v1752873840/notes-assets/images/Docker-Certified-Associate-Exam-Course-Example-Voting-Application-with-Docker-Compose/cats-vs-dogs-vote-selected.jpg)
</Frame>

## Clean Up

When you’re done testing, stop and remove all services with:

```bash theme={null}
docker-compose down
```

This command stops containers and removes the network. Volumes and images remain unless you add the `--volumes` or `--rmi all` flags.

## References and Further Reading

* [Docker Compose Installation](https://docs.docker.com/compose/install/)
* [Compose File Versioning](https://docs.docker.com/compose/compose-file/compose-versioning/)
* [Docker CLI Reference](https://docs.docker.com/engine/reference/commandline/ps/)

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