Kubeless tutorial – Kubernetes native serverless framework

kubeless is a Kubernetes-native serverless framework that lets you deploy small bits of code without having to worry about the underlying infrastructure plumbing. It leverages Kubernetes resources to provide auto-scaling, API routing, monitoring, troubleshooting and more.

Kubeless Kubernetes-native serverless framework
Image – Kubeless – Kubernetes-native serverless framework

Before we move on to tutorial, First – little bit of intro on Serverless,it allows developers to build and run applications and services without thinking about the servers actually running the code. Serverless services, or FaaS (Functions-as-a-Service) providers, instrument this concept by allowing developers to upload the code while taking care of deploying running and scaling it. AWS Lambda was the first one in the market to offer this kind.

Popular cloud providers that supports Function As A Service (FaaS) as follows:

Kubeless aims to be an open source FaaS solution to clone the functionalities of AWS Lamdba/Google Cloud Functions.

For more details on Serverless & comparison, look up here.

How it works

Serverless services or FaaS lets you run code without provisioning or managing servers (but still servers are needed). You pay only for the compute time you consume there is no charge when your code is not running. You can run code for virtually any type of application or backend service all with zero administration. Just upload your code and FaaS provider would take care of everything required to run and scale your code with high availability. You can set up your code to automatically trigger from other services or call it directly from any web or mobile app.

AWS Lambda / How it works
Image – AWS Lambda / How it works
Image- Another Sample

With Kubeless you can deploy functions without the need to build containers. These functions can be called via regular HTTP(S) calls or triggered by events submitted to message brokers like Kafka.

Currently Kubeless Functions have three possible types:

  • HTTP triggered (function will expose an HTTP endpoint)
  • Pubsub triggered (function will consume event on a specific topic; a running kafka cluster on your k8s is required)
  • Schedule triggered (function will be called on a cron schedule)

Kubeless Installation

Step #1 : Create a kubeless namespace where you will install the controller.

Create Kubeless namespace
Image – Create Kubeless namespace

Step #2 : Install the latest stable version with a kubectl create command

curl -sL https://github.com/kubeless/kubeless/releases/download/v0.3.0/kubeless-rbac-v0.3.0.yaml | kubectl create -f -
Install Kubeless
Image – Install Kubeless

You can see that few pods are being started in the kubeless namespace. Also if you can see that a few pods are being started in the kubeless namespace. The controller which will watch for function objects to be created and also two Pods to enabled PubSub function (Kafka & Zoo pods).

Step #3 : Check the status of the pods using get pods command

Check deployment status using get pods command
Image – check deployment status using get pods command

Once the controller is in ‘Running’ state,we can start deploying functions.

Deploy Function

To deploy a function, we are going use the kubeless CLI. For the function that we are going to deploy,we have to specify a run time which language the function is in.

Also we need to specify the file that contains the function, how the function will get triggered (here we are using an HTTP trigger) and finally specify the function name as a handler.

kubeless function deploy toy --runtime python2.7 --handler toy.handler --from-file toy.py --trigger-http
Deploy kubeless function
Image – Deploy kubeless function

Congrats! Now we have create new function.

We can check the list of functions with the kubeless CLI:

kubeless function ls
kubeless function ls command
Image – kubeless function ls command

Kubeless would have automatically created a Kubernetes deployment and service. You can check that a Pod containing your function is running:

kubectl get pods command
Image – kubectl get pods command

Call Function via HTTP

To test the function, call the function using the kubeless CLI command:

Call kubeless function from CLI
Image – Call kubeless function from CLI

If proxy is configured,we can call it using curl command

curl --data '{"hello":"world"}' localhost:8080/api/v1/proxy/namespaces/default/services/toy:8080/ --header "Content-Type:application/json"
Call function using curl command
Image – Call function using curl command

For viewing the logs of the function,use logs command

kubeless function logs toy
View Function logs
Image – View Function logs

To get the description of the function,use describe command like below

kubeless function describe toy
Describe command to get details of function
Image – Describe command to get details of function

To update a function use the kubeless function updatecommand. For example to replace the toy function which we have created with the method from the toy-udpate.py script, do:

kubeless function update toy --from-file toy-update.py

As clean up activity,we can also remove the functions,deployments we have created.

kubeless function delete toy
Delete command
Image – Delete command

The deployment and Kubernetes services will be removed automatically.You can use get deployments,services to check the same.

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