OpenFaaS NATS Connector

What is OpenFaaS

With OpenFaaS you can package anything as a serverless function - from Node.js to Golang to CSharp, even binaries like ffmpeg or ImageMagick.

What is NATS

NATS Server is a simple, high performance open source messaging system for cloud native applications, IoT messaging, and microservices architectures.

Why do I need a Trigger

It's not always necessary to always trigger your functions using HTTP. Sometimes we would like to trigger functions by events. NATS Provides a messaging layer between your functions and the wider internet. By using a messaging layer we can queue our function calls allowing us to trigger out functions from events happening in your application.

Why is event driven useful?

Traditionally when we wrote code our backend was one application backed by a database of some sorts. As we move to a more distributed application architecture not all of our services will be served by a single database. Using events we can abstract the database away from the calling application and use a series of serverless functions, web servers, containers and third party services without maintaining a single database for the whole application.

How does this work?

You deploy this container or pod inside your OpenFaaS Namespace. Connect up your NATS cluster by providing an environment variable and you are ready to start triggering events!

Kubernetes

• how to deploy NATS on Kubernetes!
• how to deploy OpenFaaS on Kubernetes!

Docker Swarm

• How to deploy OpenFaaS on Docker Swarm
• How to deploy NATS on Docker Swarm

Triggering your Functions

Our functions are triggered from a function.call topic we publish to NATS. See the example nats-pub*.rb files.

When publishing a message to the queue we use the following format.

Synchronous Functions

{
  function: 'figlet', 
  params: {
    body: 'Hello World'
  }
}

Asynchronous Functions

{
  function: 'figlet', 
  params: {
    callback_url: 'http://your-callback.url/example'
    body: 'Hello World'
  }
}

The NATS Client container is smart enough to distinguish between asynchronous calls and synchronous calls based on the callback_url. If it is present we will perform an async function call, else we perform a synchronous call.

Its as simple as that.

Deploying

Kubernetes

Deploy the deployment/k8s/deployment.yml to your openfaas namespace

$ kubectl apply -f deployment/k8s/deployment.yml

Docker

$ docker run -d -e NATS_HOST=nats://nats:4222 \
                -e FAAS_HOSt=http://faas:8080 \
                affixxx/openfaas-nats-connector

ToDo

• Handle OpenFaaS Gateway Authentication
• Handle NATS Authentication
• Go Rewrite
• Deploying to Docker Swarm