API REST using Google Cloud Functions (Serverless)

Serverless application has gained a lot of importance over time. It allows focussing on your app code/tests without worrying about configurations, deployment process or scalability.

We're going to create a function that will be exposed via rest URL. That function will be invoked every time a HTTP(S) request is received.

During execution, an express server will be summoned exposing our REST services.

What we are going to build?

Express API for CRUD services(create, read, update and delete) on a Firestore database.
Use Google Cloud Function to expose our Express server
Deploy our Google Cloud Function using Cloud CLI.

Creating our firebase project

In order to create our first project, let's do it here. Select add project, project's name must be unique, let's use prefix github-ring-{github_user}, github-ring-levinm in my case. Be sure to select Firestore as our database.

For creating our database, click on Develop>Database and select "start in test mode".

Initializing our project locally

We need to install firebase using NPM.



npm install -g firebase-tools

Then, let's login into our firebase account.



firebase login
........... input credentials

Initialize the project



firebase init
........ select project

It will prompt an interactive console.

Select Functions and Hosting options.
What language would you like to use to write Cloud Functions? TypeScript
Do you want to use TSLint to catch probable bugs and enforce style? Yes
Do you want to install dependencies with npm now? Yes
What do you want to use as your public directory? Press enter to select public (it is the default option)
Configure as a single-page app (rewrite all urls to /index.html)? No

We're ready, our firebase project was initialized.

Installing Express.js and dependencies



cd functions
npm install --save express body-parser

Creating our Google Cloud Function

Open src/index.ts, it will be the entrypoint for our Express.js server

Import main libraries



import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
import * as express from 'express';
import * as bodyParser from "body-parser";

Initialize firebase for accesing to its services



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

Intialize Express.js server



const app = express();
const main = express();

Configure the server.

Let's add the path used for receiving the request.
Select JSON as our main parser for processing requests body.



main.use('/api/v1', app);
main.use(bodyParser.json());

Export our function.

Last but not least, let's define our Google Cloud Function name, we are going to expose it using export. Our function will receive an express server object(this case main) which will be used for request processing. If you want more information regarding how it works, you can check this good answer on Stackoverflow



export const webApi = functions.https.onRequest(main);

Creating our first service

Let's expose a GET endpoint returning just a string.



app.get('/warm', (req, res) => {
    res.send('Calentando para la pelea');
})

Our src/index.ts file should look like this:




import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
import * as express from 'express';
import * as bodyParser from "body-parser";

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

const app = express();
const main = express();

main.use('/api/v1', app);
main.use(bodyParser.json());

export const webApi = functions.https.onRequest(main);

app.get('/warmup', (request, response) => {

    response.send('Warming up friend.');

})

Deploying our function.

Before deploying it, we need to change our config file firebase.json as follows:

{
  "functions": {
    "predeploy": [
      "npm --prefix \"$RESOURCE_DIR\" run lint",
      "npm --prefix \"$RESOURCE_DIR\" run build"
    ]
  },
  "hosting": {
    "public": "public",
    "ignore": [
      "firebase.json",
      "**/.*",
      "**/node_modules/**"
    ],
    "rewrites": [
      {
        "source": "/api/v1/**",
        "function": "webApi"
      }
    ]
  }
}

This rule allows "to route" all requests sent through api/v1 to be served by webApi function (Our exported one).

Also, Google CLI installs Typescript v2 by default. So, we need to update our typescript version >=3.3.1. You can do it in functions.package.json.

  "devDependencies": {
    "tslint": "~5.8.0",
    "typescript": "~3.3.1"
  },

Re-install dependencies.



cd functions
npm install

We are ready for deploying.



firebase deploy



.....
✔  Deploy complete!

Project Console: https://console.firebase.google.com/project/github-ring-levivm/overview
Hosting URL: https://github-ring-levivm.firebaseapp.com

If everything is ok, Hosting URL will be our Google Cloud Function endpoint.

Testing our function

Let's send a GET request using CURL



$ curl -G "https://github-ring-levivm.firebaseapp.com/api/v1/warmup"
Warming up friend.

Rest API CRUD

Let's add our CRUD endpoints. We are going to manage fights information.

Create a record

First, let's initialize our database. We open our src/index.ts and add this after admin initialization




admin.initializeApp(functions.config().firebase);
const db = admin.firestore(); // Add this

In order to create a fight record, let's create POST /fights/ endpoint. Our fight record is going to have a winner, loser and title.



app.post('/fights', async (request, response) => {
  try {
    const { winner, loser, title } = request.body;
    const data = {
      winner,
      loser,
      title
    } 
    const fightRef = await db.collection('fights').add(data);
    const fight = await fightRef.get();

    response.json({
      id: fightRef.id,
      data: fight.data()
    });

  } catch(error){

    response.status(500).send(error);

  }
});

We get our post data using request.body
We use add() method to add a new fight, if the collection doesn't exist (our case), it will create it automatically.
In order to get the actual record data, we must use get() over the ref.
Return a json using response.json.

Get a record

We create a GET /fights/:id endpoint in order to fetch a fight by id.



app.get('/fights/:id', async (request, response) => {
  try {
    const fightId = request.params.id;

    if (!fightId) throw new Error('Fight ID is required');

    const fight = await db.collection('fights').doc(fightId).get();

    if (!fight.exists){
        throw new Error('Fight doesnt exist.')
    }

    response.json({
      id: fight.id,
      data: fight.data()
    });

  } catch(error){

    response.status(500).send(error);

  }

});

We get the fight id using request.params.
We validate if the id is not blank.
We get the fight and check if it exists.
If fight doesn't exist we throw an error
If fight exists, we return the data.

Get a record list

We create a GET /fights/ endpoint.



app.get('/fights', async (request, response) => {
  try {

    const fightQuerySnapshot = await db.collection('fights').get();
    const fights = [];
    fightQuerySnapshot.forEach(
        (doc) => {
            fights.push({
                id: doc.id,
                data: doc.data()
            });
        }
    );

    response.json(fights);

  } catch(error){

    response.status(500).send(error);

  }

});

We get a collection snapshot.
We iterate over every document and push the data into an array.
We return our fight list.

Update a record

We must create a PUT /fights/:id endpoint in order to update a fight by id.



app.put('/fights/:id', async (request, response) => {
  try {

    const fightId = request.params.id;
    const title = request.body.title;

    if (!fightId) throw new Error('id is blank');

    if (!title) throw new Error('Title is required');

    const data = { 
        title
    };
    const fightRef = await db.collection('fights')
        .doc(fightId)
        .set(data, { merge: true });

    response.json({
        id: fightId,
        data
    })


  } catch(error){

    response.status(500).send(error);

  }

});

We get request data.
We validate the data
We update a record using set(data, merge: true). It means it is going to update only the fields passed on data parameter.

Deleting a record.

For deleting a fight, we need to add an endpoint DELETE /fights/:id.




app.delete('/fights/:id', async (request, response) => {
  try {

    const fightId = request.params.id;

    if (!fightId) throw new Error('id is blank');

    await db.collection('fights')
        .doc(fightId)
        .delete();

    response.json({
        id: fightId,
    })


  } catch(error){

    response.status(500).send(error);

  }

});

We get the fight id.
We use delete() in order to delete a doc instance (Remember that firestore is database based on documents( "NoSQL" ))

Our src/index.ts file should looks like this



import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
import * as express from 'express';
import * as bodyParser from "body-parser";

admin.initializeApp(functions.config().firebase);
const db = admin.firestore(); // Add this

const app = express();
const main = express();

main.use('/api/v1', app);
main.use(bodyParser.json());

export const webApi = functions.https.onRequest(main);

app.get('/warmup', (request, response) => {

    response.send('Warming up friend.');

});

app.post('/fights', async (request, response) => {
  try {
    const { winner, losser, title } = request.body;
    const data = {
      winner,
      losser,
      title
    } 
    const fightRef = await db.collection('fights').add(data);
    const fight = await fightRef.get();

    response.json({
      id: fightRef.id,
      data: fight.data()
    });

  } catch(error){

    response.status(500).send(error);

  }
});

app.get('/fights/:id', async (request, response) => {
  try {
    const fightId = request.params.id;

    if (!fightId) throw new Error('Fight ID is required');

    const fight = await db.collection('fights').doc(fightId).get();

    if (!fight.exists){
        throw new Error('Fight doesnt exist.')
    }

    response.json({
      id: fight.id,
      data: fight.data()
    });

  } catch(error){

    response.status(500).send(error);

  }
});

app.get('/fights', async (request, response) => {
  try {

    const fightQuerySnapshot = await db.collection('fights').get();
    const fights = [];
    fightQuerySnapshot.forEach(
        (doc) => {
            fights.push({
                id: doc.id,
                data: doc.data()
            });
        }
    );

    response.json(fights);

  } catch(error){

    response.status(500).send(error);

  }

});

app.put('/fights/:id', async (request, response) => {
  try {

    const fightId = request.params.id;
    const title = request.body.title;

    if (!fightId) throw new Error('id is blank');

    if (!title) throw new Error('Title is required');

    const data = { 
        title
    };
    const fightRef = await db.collection('fights')
        .doc(fightId)
        .set(data, { merge: true });

    response.json({
        id: fightId,
        data
    })


  } catch(error){

    response.status(500).send(error);

  }

});

app.delete('/fights/:id', async (request, response) => {
  try {

    const fightId = request.params.id;

    if (!fightId) throw new Error('id is blank');

    await db.collection('fights')
        .doc(fightId)
        .delete();

    response.json({
        id: fightId,
    })


  } catch(error){

    response.status(500).send(error);

  }

});

Testing

We deploy our function.



firebase deploy
....

We test all our endpoints.



# Testing create fight (POST /fights)
$ curl -d '{"winner":"levi", "losser":"henry", "title": "fight1"}' -H "Content-Type: application/json" -X POST "https://github-ring-levivm.firebaseapp.com/api/v1/fights/"

> {"id":"zC9QORei07hklkKUB1Gl","data":{"title":"fight1","winner":"levi","losser":"henry"}

# Testing  get a fight (GET /fight:id)
$ curl -G "https://github-ring-levivm.firebaseapp.com/api/v1/fights/zC9QORei07hklkKUB1wGl/"

>{"id":"zC9QORei07hklkKUB1Gl","data":{"winner":"levi","losser":"henry","title":"fight1"}}


# Testing get fights list (GET /fights/)
$ curl -G "https://github-ring-levivm.firebaseapp.com/api/v1/fights/"
> [{"id":"zC9QORei07hklkKUB1Gl","data":{"title":"fight1","winner":"levi","losser":"henry"}}]

# Testing update a fight (PUT /fights/:id)
$ curl -d '{"title": "new fight title"}' -H "Content-Type: application/json" -X PUT "https://github-ring-levivm.firebaseapp.com/api/v1/fights/zC9QORei07hklkKUB1Gl/"

> {"id":"zC9QORei07hklkKUB1Gl","data":{"title":"new fight title"}}

# Testing delete a fight (DELETE /fight/:id)
$ curl -X DELETE "https://github-ring-levivm.firebaseapp.com/api/v1/fights/zC9QORei07hklkKUB1Gl/"

> {"id":"zC9QORei07hklkKUB1Gl"}

And we are done, we have built our API Rest using Google Cloud Function (Serverless).

Note: You can check your database using Firestore interface within our Firebase console.

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