Example for Voting Application

from flask import Flask, request, make_response, render_template, g
from redis import Redis
import os, random, json, socket

option_a = os.getenv("OPTION_A", "Cats")
option_b = os.getenv("OPTION_B", "Dogs")
hostname = socket.gethostname()

app = Flask(__name__)

def get_redis():
    if not hasattr(g, 'redis'):
        g.redis = Redis(host="redis", db=0, socket_timeout=5)
    return g.redis

@app.route("/", methods=["GET", "POST"])
def vote_page():
    voter_id = request.cookies.get('voter_id')
    if not voter_id:
        voter_id = hex(random.getrandbits(64))[2:-1]

    vote = None
    if request.method == 'POST':
        redis_conn = get_redis()
        vote = request.form['vote']
        data = json.dumps({'voter_id': voter_id, 'vote': vote})
        redis_conn.rpush('votes', data)

    resp = make_response(render_template(
        'index.html',
        option_a=option_a,
        option_b=option_b,
        hostname=hostname,
        vote=vote,
    ))
    resp.set_cookie('voter_id', voter_id)
    return resp

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=80, debug=True, threaded=True)

# Use official Python runtime
FROM python:2.7-alpine
WORKDIR /app

# Install dependencies
ADD requirements.txt /app/
RUN pip install -r requirements.txt

# Copy application code
ADD . /app
EXPOSE 80

# Launch with Gunicorn
CMD ["gunicorn", "app:app", "-b", "0.0.0.0:80", "--workers", "4", "--keep-alive", "0"]

import redis.clients.jedis.Jedis;
import org.json.JSONObject;
import java.sql.*;
import java.util.List;

class Worker {
    public static void main(String[] args) {
        try {
            Jedis redis = new Jedis("redis");
            Connection dbConn = DriverManager.getConnection(
                "jdbc:postgresql://db/postgres", "postgres", "password"
            );
            System.err.println("Watching vote queue");

            while (true) {
                List<String> item = redis.blpop(0, "votes");
                String voteJSON = item.get(1);
                JSONObject voteData = new JSONObject(voteJSON);
                String voterID = voteData.getString("voter_id");
                String vote = voteData.getString("vote");

                System.err.printf("Processing vote '%s' by '%s'%n", vote, voterID);
                updateVote(dbConn, voterID, vote);
            }
        } catch (SQLException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    static void updateVote(Connection dbConn, String voterID, String vote) throws SQLException {
        PreparedStatement stmt = dbConn.prepareStatement(
            "INSERT INTO votes (id, vote) VALUES (?, ?)"
        );
        stmt.setString(1, voterID);
        stmt.setString(2, vote);
        stmt.executeUpdate();
    }
}

# Use .NET SDK image
FROM microsoft/dotnet:1.1.1-sdk
WORKDIR /code

# Copy and restore/publish the worker
ADD src/Worker /code/src/Worker
RUN dotnet restore src/Worker && \
    dotnet publish -c Release -o out src/Worker

CMD ["dotnet", "out/Worker.dll"]

const express = require('express');
const { Client } = require('pg');
const app = express();
const port = process.env.PORT || 80;

const client = new Client({
  host: 'db',
  user: 'postgres',
  password: 'password',
  database: 'postgres'
});
client.connect();

app.set('view engine', 'pug');
app.use(express.static('public'));

app.get('/', async (req, res) => {
  const result = await client.query(
    'SELECT vote, COUNT(*) AS count FROM votes GROUP BY vote'
  );
  res.render('results', { votes: result.rows });
});

app.listen(port, () => console.log(`Result app listening on ${port}`));

FROM node:5.11.0-slim
WORKDIR /app

# Global utilities
RUN npm install -g nodemon

ADD package.json /app/
RUN npm config set registry http://registry.npmjs.org && \
    npm install && npm ls

# Copy app code
ADD . /app
EXPOSE 80

CMD ["node", "server.js"]

git clone https://github.com/dockersamples/example-voting-app.git
cd example-voting-app/vote
docker build -t voting-app .

# Redis message queue
docker run -d --name redis redis:latest

# Voting UI linked to Redis on port 5000
docker run -d --name vote-ui \
  -p 5000:80 \
  --link redis:redis \
  voting-app

docker run -d --name db \
  -e POSTGRES_PASSWORD=password \
  postgres:9.4

cd ../worker
docker build -t worker-app .
docker run -d --name vote-worker \
  --link redis:redis \
  --link db:db \
  worker-app

cd ../result
docker build -t result-app .
docker run -d --name vote-result \
  -p 5001:80 \
  --link db:db \
  result-app