Working with Serverless Functions

A function is a serverless workload type which is provided by the project "Kyma" through an custom resource (CR). "Serverless" does not mean that there is no server or infrastructure involved. It simply means that the server is managed by a third party and you do not have to worry about it. You can focus on the code of your function.

Technically, Functions in Kyma relies on multiple Kubernetes resources such as Deployments, Services, HorizontalPodAutoscalers, and Jobs.

So in terms of serverless functions in Kyma, you can simply run code snippets without providing and maintaining the container image or the infrastructure. And like deployments based on containers, functions can also be scaled , exposed and subscribed to events.

Click on the "Pro" and "Con" buttons to find out more.

With Kyma, you can create functions in Node.js and Python. For this workload type, Kyma extends Kubernetes with a custom resource (CR).

A function manifest (version v1alhpa2) in YAML for a simple hello world example might look like this:

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apiVersion: serverless.kyma-project.io/v1alpha2
kind: Function
metadata:
  name: hello-kyma-function
  labels:
    app: hello-kyma-function
spec:
  runtime: nodejs16
  source:
    inline:
      dependencies: |
        {
          "name": "hello-kyma-function",
          "version": "1.0.0",
          "dependencies": {}
         }
      source: |-
       module.exports = {
           main: async function (event, context) {
             const message = `Hello ` + process.env.NAME
                + ` from the Kyma Function ${context["function-name"]}`
                + ` running on ${context.runtime}!`;
             console.log(message);
             return message;
         } 
        } 
  env:
    - name: NAME
      value: "Kyma"

The following table shows the different fields of the manifest:

Let's break down the spec part of the manifest:

To get a full list of the fields, see the Function CR documentation. There are many more fields that you can use to configure scaling, resources, gitRepository and many more.

On the Dashboard, you can navigate to the Functions section and click the Create Function button. The following image shows the form to create a function:

After creating a function, you can use the web editor to create the function code. The following image shows the web editor:

Learning how to expose a function or subscribe a function to an event will be covered in other units of this course.

Functions are a good choice if you want to run small pieces of code, for example, to process data or to respond to events. You can split your microservice into smaller functions if you want to scale it differently. Functions also supports the event-driven architecture and ensures quick deployments of your code. However, you have to consider that functions are vendor-specific and that you are limited to the supported runtime environments of Kyma.