Create a serverless, globally distributed REST API with Fauna

In this tutorial, you learn how to store and retrieve data in your Cloudflare Workers applications by building a REST API that manages an inventory catalog using Fauna as its data layer.

Learning goals

• How to store and retrieve data from Fauna in Workers.
• How to use Wrangler to store secrets securely.
• How to use Hono as a web framework for your Workers.

Building with Fauna, Workers, and Hono enables you to create a globally distributed, strongly consistent, fully serverless REST API in a single repository.

Fauna is a document-based database with a flexible schema. This allows you to define the structure of your data – whatever it may be – and store documents that adhere to that structure. In this tutorial, you will build a product inventory, where each product document must contain the following properties:

• title - A human-friendly string that represents the title or name of a product.
• serialNumber - A machine-friendly string that uniquely identifies the product.
• weightLbs - A floating point number that represents the weight in pounds of the product.
• quantity A non-negative integer that represents how many items of a particular product there are in the inventory.

Documents are stored in a collection. Collections in document databases are groups of related documents.

For this tutorial, all API endpoints are public. However, Fauna also offers multiple avenues for securing endpoints and collections. Refer to Choosing an authentication strategy with Fauna for more information on authenticating users to your applications with Fauna.

Before you start

All of the tutorials assume you have already completed the Get started guide, which gets you set up with a Cloudflare Workers account, C3, and Wrangler.

Set up Fauna

Create your database

Open the Fauna dashboard in your browser and log in to your Fauna account.

Fauna Account

If you do not have a Fauna account, sign up and deploy this template using the free tier.

In the Fauna dashboard:

1. Select CREATE DATABASE.
2. Provide a valid name.
3. Select a Region Group.
4. Select CREATE.

Create a collection

To create a collection named Products, enter the FQL query in the SHELL window on right side of the screen.

Create a new collection

Collection.create({ name: "Products" })

Select Run. You will see an output similar to the following.

Output

{
  name: "Products",
  coll: Collection,
  ts: "<timestamp>",
  indexes: {},
  constraints: []
}

Create a secret key

You must create a secret key to connect to the database from your Worker.

To create a secret key:

1. Go to Explorer in the Fauna dashboard.
2. Hover over your database name, and select the key icon to manage your keys.
3. Choose Server Role and enter a key name.

The Fauna dashboard displays the key’s secret. Copy and save this server key to use in a later step.

Protect your keys

Server keys can read and write all documents in all collections and can call all user-defined functions (UDFs). Protect server keys and do not commit them to source control repositories.

Manage your inventory with Workers

Create a new Worker project

Create a new project by using C3.

npm

$ npm create cloudflare@latest {props.one}

yarn

$ yarn create cloudflare@latest {props.one}

To continue with this guide:

• For What would you like to start with?, select Framework Starter.
• For Which development framework do you want to use?, select Hono.
• For, Do you want to deploy your application?, select No.

Then, move into your newly created directory:

$ cd fauna-workers

Update the wrangler.toml file to set the name for the Worker.

wrangler.toml

name = "fauna-workers"

Add your Fauna secret key as a secret

Before developing your Worker, add your Fauna secret key as a secret.

There are two types of secrets for development or production.

For development, add a .dev.vars file on the project root and write your secret.

.dev.vars

FAUNA_SECRET=<YOUR SECRET>

For production, store your secret safely with wrangler secret put command:

Store your Fauna secret

$ npx wrangler secret put FAUNA_SECRET

When prompted, paste the Fauna server secret you obtained earlier.

The FAUNA_SECRET secret is now injected automatically into your Worker code at runtime.

Install dependencies

Install the Fauna JavaScript driver in your newly created Worker project.

npm

Install the Fauna driver

$ npm install fauna

yarn

Install the Fauna driver

$ yarn add fauna

Base inventory logic

Replace the contents of your src/index.ts file with the skeleton of your API:

src/index.ts

import { Hono } from 'hono';
import { Client, fql, ServiceError } from 'fauna';

type Bindings = {
  FAUNA_SECRET: string;
};

type Variables = {
  faunaClient: Client;
};

type Product = {
  id: string;
  serialNumber: number;
  title: string;
  weightLbs: number;
  quantity: number;
};

const app = new Hono<{ Bindings: Bindings; Variables: Variables }>();

app.use('*', async (c, next) => {
  const faunaClient = new Client({
    secret: c.env.FAUNA_SECRET,
  });
  c.set('faunaClient', faunaClient);
  await next();
});

app.get('/', (c) => {
  return c.text('Hello World');
});

export default app;

This is custom middleware to initialize the Fauna client and set the instance with c.set() for later use in another handler:

Custom middleware for the Fauna Client

app.use('*', async (c, next) => {
  const faunaClient = new Client({
    secret: c.env.FAUNA_SECRET,
  });
  c.set('faunaClient', faunaClient);
  await next();
});

You can access the FAUNA_SECRET environment variable from c.env.FAUNA_SECRET. Workers run on a custom JavaScript runtime instead of Node.js, so you cannot use process.env to access your environment variables.

Create product documents

Add your first Hono handler to the src/index.ts file. This route accepts POST requests to the /products endpoint:

Create product documents

app.post('/products', async (c) => {
  const { serialNumber, title, weightLbs } = await c.req.json<Omit<Product, 'id'>>();
  const query = fql`Products.create({
    serialNumber: ${serialNumber},
    title: ${title},
    weightLbs: ${weightLbs},
    quantity: 0
  })`;
  const result = await c.var.faunaClient.query<Product>(query);
  return c.json(result.data);
});

Handler order

In Hono, you should place your handler below the custom middleware. This is because middleware and handlers are executed in sequence from top to bottom. If you place the handler first, you cannot retrieve the instance of the Fauna client using c.var.faunaClient.

This route applied an FQL query in the fql function that creates a new document in the Products collection:

Create query in FQL inside JavaScript

fql`Products.create({
  serialNumber: ${serialNumber},
  title: ${title},
  weightLbs: ${weightLbs},
  quantity: 0
})`

To review what a document looks like, run the following query. In the Fauna dashboard, go to Explorer > Region name > Database name like a cloudflare_rest_api > the SHELL window:

Create query in pure FQL

Products.create({
  serialNumber: "A48432348",
  title: "Gaming Console",
  weightLbs: 5,
  quantity: 0
})

Fauna returns the created document:

Newly created document

{
  id: "<document_id>",
  coll: Products,
  ts: "<timestamp>",
  serialNumber: "A48432348",
  title: "Gaming Console",
  weightLbs: 5,
  quantity: 0
}

Examining the route you create, when the query is successful, the data newly created document is returned in the response body:

Return the new document data

return c.json({
  productId: result.data,
});

Error handling

If Fauna returns any error, an exception is raised by the client. You can catch this exception in app.onError(), then retrieve and respond with the result from the instance of ServiceError.

Handle errors

app.onError((e, c) => {
  if (e instanceof ServiceError) {
    return c.json(
      {
        status: e.httpStatus,
        code: e.code,
        message: e.message,
      },
      e.httpStatus
    );
  }
  console.trace(e);
  return c.text('Internal Server Error', 500);
});

Retrieve product documents

Next, create a route that reads a single document from the Products collection.

Add the following handler to your src/index.ts file. This route accepts GET requests at the /products/:productId endpoint:

Retrieve product documents

app.get('/products/:productId', async (c) => {
  const productId = c.req.param('productId');
  const query = fql`Products.byId(${productId})`;
  const result = await c.var.faunaClient.query<Product>(query);
  return c.json(result.data);
});

The FQL query uses the byId() method to retrieve a full document from the Productions collection:

Retrieve a document by ID in FQL inside JavaScript

fql`Products.byId(productId)`

If the document exists, return it in the response body:

Return the document in the response body

return c.json(result.data);

If not, an error is returned.

Delete product documents

The logic to delete product documents is similar to the logic for retrieving products. Add the following route to your src/index.ts file:

Delete product documents

app.delete('/products/:productId', async (c) => {
  const productId = c.req.param('productId');
  const query = fql`Products.byId(${productId})!.delete()`;
  const result = await c.var.faunaClient.query<Product>(query);
  return c.json(result.data);
});

The only difference from the previous route is that you use the delete() method, combined with the byId() method, to delete a document.

When the delete operation is successful, Fauna returns the deleted document and the route forwards the deleted document in the response’s body. If not, an error is returned.

Test and deploy your Worker

Before deploying your Worker, test it locally by using Wrangler’s dev command:

npm

Develop your Worker

$ npm run dev

yarn

Develop your Worker

$ yarn dev

Once the development server is up and running, start making HTTP requests to your Worker.

First, create a new product:

Create a new product

$ curl \
    --data '{"serialNumber": "H56N33834", "title": "Bluetooth Headphones", "weightLbs": 0.5}' \
    --header 'Content-Type: application/json' \
    --request POST \
    http://127.0.0.1:8787/products

You should receive a 200 response similar to the following:

Create product response

{
  "productId": "<document_id>"
}

Note

Copy the productId value for use in the remaining test queries.

Next, read the document you created:

Read a document

$ curl \
    --header 'Content-Type: application/json' \
    --request GET \
    http://127.0.0.1:8787/products/<document_id>

The response should be the new document serialized to JSON:

Read product response

{
  "coll": {
    "name": "Products"
  },
  "id": "<document_id>",
  "ts": {
    "isoString": "<timestamp>"
  },
  "serialNumber": "H56N33834",
  "title": "Bluetooth Headphones",
  "weightLbs": 0.5,
  "quantity": 0
}

Finally, deploy your Worker using the wrangler deploy command:

npm

Deploy your Worker

$ npm run deploy

yarn

Deploy your Worker

$ yarn deploy

This publishes the Worker to your *.workers.dev subdomain.

Update inventory quantity

As the last step, implement a route to update the quantity of a product in your inventory, which is 0 by default.

This will present a problem. To calculate the total quantity of a product, you first need to determine how many items there currently are in your inventory. If you solve this in two queries, first reading the quantity and then updating it, the original data might change.

Add the following route to your src/index.ts file. This route responds to HTTP PATCH requests on the /products/:productId/add-quantity URL endpoint:

Update inventory quantity

app.patch('/products/:productId/add-quantity', async (c) => {
  const productId = c.req.param('productId');
  const { quantity } = await c.req.json<Pick<Product, 'quantity'>>();
  const query = fql`Products.byId(${productId}){ quantity : .quantity + ${quantity}}`;
  const result = await c.var.faunaClient.query<Pick<Product, 'quantity'>>(query);
  return c.json(result.data);
});

Examine the FQL query in more detail:

Update query in FQL inside JavaScript

fql`Products.byId(${productId}){ quantity : .quantity + ${quantity}}`;

Consistency guarantees in Fauna

Even if multiple Workers update this quantity from different parts of the world, Fauna guarantees the consistency of the data across all Fauna regions. This article on consistency explains how Fauna’s distributed protocol works without the need for atomic clocks.

Test your update route:

Update product inventory

$ curl \
    --data '{"quantity": 5}' \
    --header 'Content-Type: application/json' \
    --request PATCH \
    http://127.0.0.1:8787/products/<document_id>/add-quantity

The response should be the entire updated document with five additional items in the quantity:

Update product response

{
  "quantity": 5
}

Update your Worker by deploying it to Cloudflare.

npm

Update your Worker in Cloudflare

$ npm run deploy

yarn

Update your Worker in Cloudflare

$ yarn deploy

Related resources

In this tutorial, you learned how to use Fauna with Cloudflare Workers to create a globally distributed, strongly consistent, next-generation serverless REST API that serves data quickly to a worldwide audience.

If you would like to review the full source code for this application, you can find the repository on GitHub.