Serverless with Kubernetes (Knative)
Explore how platforms like Knative enable serverless functions and event-driven architectures on top of Kubernetes.
Serverless with Kubernetes (Knative) is a free Docker & Kubernetes for Developers lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Docker & Kubernetes for Developers learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Serverless & Kubernetes
Welcome to the world of serverless on Kubernetes! Serverless computing allows you to run code without provisioning or managing servers, focusing purely on your application logic.
By combining serverless with Kubernetes, you get the benefits of both: the agility and cost-efficiency of serverless, backed by the robust, scalable, and portable infrastructure management of Kubernetes.
Knative: K8s Serverless
Knative is an open-source platform that extends Kubernetes to provide components for deploying, running, and managing serverless workloads. It simplifies the complexities of running serverless applications.
Knative has two main components: Knative Serving, which handles request-driven services, and Knative Eventing, for event-driven architectures.
Knative Serving Basics
Knative Serving is designed for deploying and managing stateless services. It takes care of:
- Rapid Deployment: Quickly deploys container images.
- Auto-scaling: Scales services up and down based on demand, even to zero instances when idle.
- Revision Management: Provides immutable revisions for easy rollbacks and traffic splitting.
It's perfect for web applications, APIs, and microservices.
Serving: Services & Revisions
Key concepts in Knative Serving:
- Service: The top-level resource, defining the desired state of your application.
- Revision: An immutable snapshot of your service's code and configuration at a specific point in time. New deployments create new revisions.
- Route: Manages network traffic to one or more revisions, enabling features like A/B testing or gradual rollouts.
These components work together to provide a robust deployment and scaling mechanism.
Defining a Knative Service
A Knative Service is defined using a YAML manifest, much like other Kubernetes resources. This example defines a simple 'hello-knative' service using a pre-built image.
Notice the serving.knative.dev/v1 API version and the kind: Service.
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: hello-knative
spec:
template:
spec:
containers:
- image: docker.io/knative/helloworld-go
env:
- name: TARGET
value: "Knative"Simple Serverless App
This is a basic Python Flask application that Knative would deploy. It listens for HTTP requests and responds with a greeting, using an environment variable for customization. Knative handles the containerization, deployment, and scaling of this app.
from flask import Flask
import os
app = Flask(__name__)
@app.route('/')
def hello():
target = os.environ.get('TARGET', 'World')
return f'Hello {target}!\n'
if __name__ == '__main__':
app.run(host='0.0.0.0', port=8080)Knative Eventing
Knative Eventing enables event-driven architectures on Kubernetes. It allows services to communicate asynchronously by sending and receiving events, decoupling the event producers from consumers.
This is crucial for building reactive systems that respond to various changes, like data updates, file uploads, or scheduled tasks.
Eventing: Sources & Brokers
Key components in Knative Eventing:
- Event Source: Generates events from various systems (e.g., Kafka, GitHub, CronJob, S3).
- Broker: A central messaging hub where event sources send events. It abstracts the underlying messaging system.
- Trigger: Filters events from a Broker based on attributes and routes them to a specific event consumer (often a Knative Service).
This flow enables flexible and scalable event processing.
Example Event Flow
Imagine you have a service that processes new images. You can set up an Event Source that monitors an S3 bucket for new image uploads.
When an image is uploaded, the source sends an event to a Broker. A Trigger, configured to filter for 'new S3 image' events, then forwards that event to your image processing Knative Service.
Your service processes the image, scales down when idle, and you only pay for the compute used during processing.
Knative Knowledge Check
Which Knative component is primarily responsible for automatically scaling services up or down based on incoming requests, including scaling to zero when idle?
Knative Recap
In this lesson, you explored how Knative brings serverless capabilities to Kubernetes. You learned about:
- Knative Serving: For deploying and auto-scaling request-driven services.
- Knative Eventing: For building event-driven architectures with sources, brokers, and triggers.
Knative empowers developers to build and run serverless applications with the control and flexibility of Kubernetes.
Frequently asked questions
Is the “Serverless with Kubernetes (Knative)” lesson free?
Yes — the full text of “Serverless with Kubernetes (Knative)” is free to read here on the web, and the Docker & Kubernetes for Developers course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Docker & Kubernetes for Developers course, upgrade to CoddyKit PRO.
What will I learn in “Serverless with Kubernetes (Knative)”?
Explore how platforms like Knative enable serverless functions and event-driven architectures on top of Kubernetes. You practise Docker & Kubernetes for Developers with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Docker & Kubernetes for Developers?
No prior experience is required. Docker & Kubernetes for Developers on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Serverless with Kubernetes (Knative)” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Docker & Kubernetes for Developers lesson?
Yes. Every Docker & Kubernetes for Developers lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Custom Resource Definitions (CRDs)
- The Operator Pattern in Kubernetes
- Serverless with Kubernetes (Knative)
- Extending the API Server with Admission Webhooks