Kubernetes, as a container orchestration platform, manages the deployment, scaling, and operation of application containers across clusters of hosts. A reverse proxy in a Kubernetes environment plays a crucial role in routing requests to the appropriate services and providing load balancing, SSL termination, and other essential features. This guide will walk you through the fundamentals of how a reverse proxy works in Kubernetes, its use cases, and how to set it up.
What is a Reverse Proxy?
Let’s start with the basics. A reverse proxy is a server that sits between client devices and backend servers, forwarding client requests to the appropriate backend service. Unlike a forward proxy, which directs outbound traffic from clients to the internet, a reverse proxy routes inbound traffic from clients to the appropriate backend service within a network.
Kubernetes Reverse Proxy
A Kubernetes reverse proxy is a network component deployed within a Kubernetes cluster that acts as an intermediary when the client requests access to services within the cluster. Instead of clients directly connecting to individual services, they route their requests through the reverse proxy. The reverse proxy then decides which service to send the request to, based on the rules you set up.
In Kubernetes, a reverse proxy is commonly used to:
Route requests to different services based on URL paths or hostnames.
Load balance requests across multiple instances of a service.
Terminate SSL/TLS connections.
Handle authentication and authorization.
Here is a quick video: How reverse proxy works in Kubernetes.
These are the six main components of setting up a reverse proxy in Kubernetes.
1. Ingress Controller
In Kubernetes, the Ingress controller is a specialized reverse proxy that manages access to services from outside the Kubernetes cluster. It is responsible for interpreting Ingress resources and configuring the reverse proxy accordingly.
2. Service Discovery
Kubernetes services use labels to enable service discovery. The reverse proxy uses these labels to dynamically route traffic to the correct service instance. For example, a request to my-app.example.com could be routed to a service labeled app=my-app.
3. Load Balancing
The reverse proxy in Kubernetes can distribute incoming requests across multiple pods (instances) of a service, ensuring even load distribution. This is often achieved using algorithms like round-robin, least connections, or IP hash.
4. SSL Termination
The reverse proxy can handle SSL termination by decrypting HTTPS traffic and forwarding the unencrypted traffic to the backend services. This offloads the SSL processing from the backend services, improving their performance.
5. Path and Host-based Routing
The reverse proxy can route requests based on the URL path or the hostname. For example, requests to example.com/api/ can be routed to one service, while requests to example.com/app/ can be routed to another.
6. Authentication and Authorization:
Reverse proxies can integrate with identity providers and enforce authentication and authorization policies, ensuring that only authenticated and authorized users can access certain services.
4 Steps of Setting Up a Reverse Proxy in Kubernetes
1. Install an Ingress Controller
Choose and install an Ingress controller suitable for your environment. Common options include:
Pomerium
NGINX Ingress Controller
Traefik
HAProxy Ingress
Contour
2. Define Ingress Resources
Create Ingress resources to define the routing rules for your services. Below is an example of an Ingress resource:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: my-app-ingress
spec:
rules:
- host: my-app.example.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: my-app-service
port:
number: 80
To enable SSL termination, you need to create a Kubernetes Secret containing your SSL certificate and key, and then reference this secret in your Ingress resource:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: my-app-ingress
spec:
tls:
- hosts:
- my-app.example.com
secretName: my-app-tls
rules:
- host: my-app.example.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: my-app-service
port:
number: 80
4. Deploy and Test
Apply your Ingress resource to the cluster and test the setup by accessing your application through the specified host.
How Pomerium Enables K8s Reverse Proxy
Pomerium is a robust and flexible reverse proxy solution for Kubernetes, offering enhanced security, simplified management, and seamless integration with identity providers. Pomerium operates as an Ingress controller within a Kubernetes cluster. It intercepts traffic destined for your applications and services, enforcing identity and context-based access policies before routing the requests to their final destinations. Here’s a breakdown of how Pomerium acts as a reverse proxy within Kubernetes:
Ingress Controller: Pomerium acts as a secure-by-default Ingress controller to implement Kubernetes reverse Proxy. It manages traffic routing and access policies using Kubernetes Ingress resources, which simplifies the configuration and management of routes. This enables native GitOps-style workflows, where changes to routes and access policies can be managed through pull requests.
Identity-Aware Proxy: Pomerium integrates with your Identity Provider (IdP) to enforce authentication and authorization policies. This allows you to secure access to applications based on user identity, group membership, and other contextual information like device type and location.
Secure Traffic Management: Pomerium supports advanced routing features such as path-based routing, regular expression matching, and mutual TLS (mTLS) for secure communication between clients and backend services. Additionally, it can handle both HTTP and TCP traffic, making it versatile for a variety of application protocols.
Load Balancing and Service Proxy: By default, Pomerium routes traffic directly to service endpoints, bypassing the Kubernetes service proxy, which can improve performance. However, it can also be configured to work within a service mesh like Istio if required.
Metrics and Monitoring: Pomerium provides comprehensive Prometheus-style metrics, which are essential for monitoring and managing the performance and security of your applications in real time.
Benefits of Using Pomerium in Kubernetes
Zero Trust Security: Pomerium enforces a zero-trust security model by ensuring that each request is authenticated and authorized based on the identity and context of the user. This significantly reduces the attack surface compared to traditional network security models.
Simplified Management: The integration of Pomerium with Kubernetes’ native Ingress resources allows for simplified route and policy management, making it easier to deploy, update, and manage secure routes across multiple environments.
Enhanced Security Features: Pomerium offers advanced security features such as mTLS, identity verification, and granular access control policies, which are essential for protecting sensitive applications and data.
Scalability and Flexibility: With support for multiple replicas and service scaling, Pomerium ensures that your applications remain performant and resilient under varying loads.
Summary of Reverse Proxy in Kubernetes
A reverse proxy in Kubernetes is a server that sits between client applications and backend services, forwarding client requests to the appropriate backend services. It is an essential component of Kubernetes’ security posture. Pomerium is an ideal choice for organizations looking to implement a zero-trust security model with a strong Kubernetes reverse proxy solution. In Kubernetes, the Pomerium Ingress Controller is one of the most popular tools for implementing a reverse proxy. NGINX Ingress Controller, Traefik, and HAProxy are also commonly used as reverse proxies to manage and secure traffic to and from services within the cluster.
