Extend your API with Serverless Functions and API Gateways

Victor Martin
May 11 · 6 min read

Start here to explore how you can extend your APIs with API Gateway and Serverless Functions. The advantage is that you will use the latest libraries and technologies, not to worry about provisioning and scaling to match your workload demand.

Serverless technology is here to stay.

Serverless is the future of the Cloud.

Learn more about API Gateways and why you need one on my previous article:

We will build a serverless function that accepts text files and respond with the gzip file. We will make your function accessible with a secure API Gateway Endpoint.

We will use Oracle Cloud Infrastructure (OCI), specifically Oracle Functions and OCI API Gateway. They are both within the Free Tier of Oracle Cloud.

Do you have an Oracle Cloud Account? If not, you can create one here:

Remember, Oracle Cloud does not charge you anything unless you explicitly request the upgrade to pay as you go. No surprises.

Oracle Cloud Sign-up for free

Network and Security

Let’s start with the foundations: network and security.


We need to create a Policy to enable API Gateway to use Oracle Functions.

Click Create Policy. Set a Name, and Description. Check Show manual editor and write the following policy and click Create:

allow any-user to use functions-family in tenancy


We need to create a Virtual Cloud Network (VCN) representing the network fabric where API Gateway is going to live.

Menu for Virtual Cloud Network

Click Start VCN Wizard and create a VCN with Internet Connectivity. Select a VCN Name (mine is serverless) and leave everything else as default. Click Next and Create.

When the creation is completed, you will have two Subnets (one public and one private).

Click on your Public subnet:

Click Default Security List for serverless. And then click Add Ingress Rule. Set the values as follows:


Destination Port Range: 443

Description: Allow ingress traffic on TCP/443

API Gateways will listen into port 443. The ingress rule we have just created will allow that traffic from the Internet into the public subnet.

Serverless Function

Imagine you have several serverless functions, and they split across several bounded contexts or apps. That is why you need to create an Application in Oracle Functions, to aggregate similar serverless functions. Let’s do that.

Click Create Application and set the Name, VCN and Private Subnet.

We will click Getting Started on the side menu and use the Cloud Shell guide to configure and get our Serverless function deployed. Stop when you reach step seven and make sure you change [OCIR-REPO] in step 4 for a registry repository name you like, for example, tools.

At this point, we will create our serverless function to receive incoming text files and respond with the text file gzipped. Finally, we will deploy the function.

Start by building the function in Cloud Shell with:

fn init --runtime python zipper

Make sure you change the directory of the new Function zipper:

cd zipper

Edit the func.py file with the following code:

import io
import logging
import gzip
from fdk import responsedef handler(ctx, data: io.BytesIO = None):
logging.getLogger().info("gzipping body")
gz_data = gzip.compress(data.getvalue())
logging.getLogger().info("sending response")
return response.Response(
headers={"Content-Type": "application/gzip"}

Deploy function with the following command:

fn deploy --app tools

API Gateway

Time to create an OCI API Gateway.

Click Create Gateway and set the following values:

Name: tools

Type: Public

Virtual Cloud Network: serverless

Subnet: Public Subnet-serverless

When the Gateway is Active, it is time to create a Deployment.

The Deployment is just the representation of an API runtime with all the routing to backend APIs.

Click Deployments on the side menu of your new tools Gateway; click Create Deployment.

Select From Scratch and set a Name (for example tools).

Make sure the Path Prefix is /tools/v1.

Click Next; then, we will create one Route pointing to our zipper serverless function.

Path: /zipper

Methods: POST

Type: Oracle Functions

Application: tools

Function Name: zipper

Invoke your Serverless Function

We will use cURL to make an HTTPS request to your API Gateway that will redirect the request to your Serverless Function.

Copy the URL of the API Gateway Endpoint from the detail page of API Gateway Deployment:

In Cloud Shell, we will create a file.txt with content Hello with the following command:

echo "Hello" > file.txt

Then, we will execute the request (replace <APIGW_ENDPOINT> with the value for your API Gateway Endpoint):

curl -XPOST -H "Content-Type: text/plain" -d @file.txt <APIGW_ENDPOINT>/tools/v1/zipper > response.txt.gz

The result is going to be a response.txt.gz that we can unzip with the following command:

gzip -d response.txt.gz

Then we can check the content of the new file, it should say Hello:

cat response.txt

Congratulations! Feel free to redirect existing requests to your existing API, and extend your API with Oracle Functions to forget about low-level IaaS provisioning. Scale-up and down as needed and pay only for what you use.

Want to learn more?

There are periodic free training sessions, around 1 hour long, delivered by experts and Oracle Cloud Advocates. These are instructor-led training. You can follow along with our team to solve your questions on the spot.

Join me on Oracle Cloud Infrastructure Discord Channel for any question.

And keep tuned for more articles about the amazing things you can build with Oracle Cloud.

I am Victor Martin, a Software Developer. I deploy on Oracle Cloud Infrastructure.

Feel free to get connected with me on LinkedIn.

I am also interested in Scuba diving and space engineering. Happy to help, everything is easier than rocket science!

Oracle Developers

A community for developers by developers.

Oracle Developers

Aggregation of articles from Oracle engineers, Groundbreaker Ambassadors, Oracle ACEs, and Java Champions on all things Oracle technology. The views expressed are those of the authors and not necessarily of Oracle.

Victor Martin

Written by

Principal Cloud Engineer. All opinions are my own. @OracleCloudInfrastructure

Oracle Developers

Aggregation of articles from Oracle engineers, Groundbreaker Ambassadors, Oracle ACEs, and Java Champions on all things Oracle technology. The views expressed are those of the authors and not necessarily of Oracle.