The Kubernetes Gateway API represents the evolution of traffic management, designed to supersede the traditional Ingress API by addressing limitations like annotation sprawl and lack of portability. In the context of the CKA exam and general Services & Networking, the Gateway API introduces a role-…The Kubernetes Gateway API represents the evolution of traffic management, designed to supersede the traditional Ingress API by addressing limitations like annotation sprawl and lack of portability. In the context of the CKA exam and general Services & Networking, the Gateway API introduces a role-oriented resource model that decouples infrastructure provisioning from application routing. It utilizes three primary Custom Resource Definitions (CRDs):
1. GatewayClass: Managed by infrastructure providers, this defines the controller implementation (e.g., Istio, NGINX, or cloud-provider load balancers).
2. Gateway: Managed by cluster operators, this resource instantiates the load balancer, defining entry points (listeners), ports, and protocols.
3. HTTPRoute: Managed by developers, this defines the actual routing logic (path matching, header manipulation) and links to backend Services.
To manage Ingress traffic using this API, you typically define an HTTPRoute that explicitly references a specific Gateway using the 'parentRefs' field. This binding mechanism allows for advanced patterns like cross-namespace routing and traffic splitting (e.g., canary deployments) without relying on non-standard annotations. Unlike the monolithic Ingress resource, the Gateway API allows multiple routes to attach to a single listener, enabling different teams to manage their routing rules independently while sharing a single physical load balancer. For CKA scenarios, you should focus on understanding how to configure 'match' rules, 'backendRefs', and how to bind routes to gateways to successfully direct external traffic to internal ClusterIP services.
Kubernetes Gateway API: Managing Ingress Traffic
What is the Gateway API? The Gateway API is an open-source project managed by the SIG-NETWORK community that represents the next generation of traffic management in Kubernetes. While the traditional Ingress resource was simple, it lacked standardization for advanced features, leading to a proliferation of implementation-specific annotations. The Gateway API is a collection of resources (CRDs) that models service networking as an expressive, extensible, and role-oriented standard.
Why is it Important? It is designed to solve the limitations of the original Ingress API. It introduces a role-based architecture that separates the concerns of the infrastructure provider (who manages the Load Balancer) from the application developer (who manages the Routing). It supports advanced traffic management features out-of-the-box, such as traffic splitting (canary releases), header-based matching, and cross-namespace routing, without relying on non-standard annotations.
How it Works: The Core Resources Unlike Ingress, which is a single object, Gateway API relies on three primary resources: 1. GatewayClass: Managed by the infrastructure provider. It acts as a template defining the controller implementation (e.g., Nginx, Istio, Cilium). 2. Gateway: Managed by the cluster operator. It is the instantiation of a load balancer. It defines Listeners (ports, protocols like HTTP/HTTPS) and specifies which GatewayClass to use. 3. HTTPRoute: Managed by the application developer. It defines the routing logic (hostnames, paths, headers) and attaches to a specific Gateway to route traffic to backend Services.
How to Answer Questions in the Exam In the CKA exam, you will likely be asked to expose a specific service using the Gateway API. Follow these steps: 1. Verify CRDs: Ensure the Gateway API CRDs are installed (kubectl get gatewayclass). 2. Create the Gateway: Define a Gateway manifest that listens on the requested port (usually 80). You must specify the gatewayClassName provided in the question. 3. Create the HTTPRoute: Define an HTTPRoute that references the Gateway you just created (via parentRefs). Define the rules to match traffic (e.g., path prefix) and point the backendRefs to the target Kubernetes Service and port.
Exam Tips: Answering Questions on Use the Gateway API to manage Ingress traffic 1. Hierarchy Matters: Remember the chain: GatewayClass defines the 'Who', Gateway defines the 'Where' (ports/IPs), and HTTPRoute defines the 'How' (routing logic). 2. ParentRefs: When writing the HTTPRoute, the parentRefs section is critical. It must explicitly match the name (and namespace if different) of the Gateway object. 3. Syntax Precision: Unlike Ingress, Gateway API uses matches for routing. For example, to match a path, you use path: type: PathPrefix, value: /my-app. Memorize or bookmark the documentation for HTTPRoute spec structure. 4. Check Status: After applying your manifests, always check kubectl get gateway and kubectl get httproute. Look for the PROGRAMMED status to be True. If it is false, describe the object to check for configuration errors like port conflicts or missing GatewayClasses. 5. Documentation Shortcut: In the exam terminal, you can often use kubectl explain httproute.spec.rules to find the exact JSON structure if you forget the specific field names.