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https://github.com/seriousme/docker-voting-app-gcp

Docker Voting App done Serverless Style using GCP
https://github.com/seriousme/docker-voting-app-gcp

firebase-database firebase-functions gcp serverless

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Docker Voting App done Serverless Style using GCP

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README 

        
# Docker Voting App done Serverless Style using Google Firebase



## Introduction



I was reading [Deploy the Voting App to AWS ECS with Fargate] by Tony Pujals

where he describes how to run the [Docker Voting app demo] on AWS using [AWS

Fargate]



[deploy the voting app to aws ecs with fargate]: https://medium.com/@tonypujals/deploy-the-voting-app-to-aws-ecs-with-fargate-

[docker voting app demo]: https://github.com/subfuzion/docker-voting-app-nodejs

[aws fargate]: https://aws.amazon.com/fargate/



Of course I understand that the Docker Voting app is a showcase of Docker

technology and that it's not the most exciting application from a business

perspective. I also understand that people want to show how you can take Docker

technology to AWS. However in my mind I started wondering: if I would take this

to AWS would I be following the same path ? Or would I go Serverless ?



Given the title: I went Serverless!



The first iteration was on [AWS using AWS ApiGateway and AWS DynamoDB only]. And

then I figured that it would be fun to try it on Google Cloud as well. Given the

simplicity of the problem I went for [Google Firebase].



[aws using aws apigateway and aws dynamodb only]: https://github.com/seriousme/docker-voting-app-aws

[google firebase]: https://firebase.google.com/



## Figuring out the API



Looking at the sources of the original voting app there are two endpoints:



* POST /vote where you can post a vote by posting JSON like `{"vote":"a"}` or

  `{"vote":"b"}`

* GET /results which will give you results like:



```json

{

  "success": true,

  "result": {

    "a": 0,

    "b": 0

  }

}

```



Firebase does nothing with automatic schema validation like the AWS API

ApiGateway does. So creating a JSON schema is of no use here. Given the specific

formats of the API a simple route to a solution is to use [Firebase Functions]

with data stored using [Firebase Realtime Database].



[firebase functions]: https://firebase.google.com/products/functions/

[firebase realtime database]: https://firebase.google.com/products/realtime-database/



And then it becomes a rather simple exercise:



## Import dependencies and initialize the connection to the database



```js

const functions = require("firebase-functions");

const admin = require("firebase-admin");

admin.initializeApp(functions.config().firebase);

```



## Define the route for /vote



```js

exports.vote = functions.https.onRequest((request, response) => {

  const vote = request.body.vote;

  if (vote === "a" || vote === "b") {

    const resultsRef = admin.database().ref("/result");

    const ref = resultsRef.child(vote);

    ref.transaction(currentVotes => {

      // If result.{vote} has never been set, currentVotes will be `null`.

      return (currentVotes || 0) + 1;

    });

    response.send("You voted: " + vote);

  } else {

    response.status(400).send("Invalid request");

  }

});

```



## Define the route for /results



```js

exports.results = functions.https.onRequest((request, response) => {

  var results = {

    success: true,

    result: {

      a: 0,

      b: 0

    }

  };

  return admin

    .database()

    .ref("/result")

    .once("value")

    .then(snapshot => {

      const resultsData = snapshot.val();

      results.result.a = resultsData.a || 0;

      results.result.b = resultsData.b || 0;

      response.json(results);

      return;

    })

    .catch(_ => {

      response.json(results);

    });

});

```



The data might not exist in the database yet when `/results` is being called

therefore this function takes care of that using `resultsData.a || 0` and

through the `.catch` handler.



The complete code can be found in [functions/index.js]. All the rest of the

project is auto generated using [firebase-tools].



[functions/index.js]: https://github.com/seriousme/docker-voting-app-gcp/blob/master/functions/index.js

[firebase-tools]: https://www.npmjs.com/package/firebase-tools