Kubernetes Gateway API provides a role-oriented model for application traffic. Instead of placing every routing concern into one Ingress object, infrastructure owners can manage GatewayClass and Gateway resources while application teams manage HTTPRoute resources. Migration should be driven by controller support and operational requirements, not by assuming every Ingress annotation has a direct equivalent.
Map the existing traffic model
Inventory hosts, paths, TLS certificates, redirects, header rules, authentication, timeouts and controller-specific annotations. Identify which rules are portable and which depend on vendor extensions. Capture current behavior with integration tests before changing the data plane.
Understand the resource roles
GatewayClass identifies the controller implementation. A Gateway defines listeners and infrastructure attachment. HTTPRoute expresses host and path matching plus backend references. The separation lets platform teams control exposure while application teams own route intent.
Check controller conformance
Gateway API resources are only useful when the installed controller supports the features you need. Confirm the supported API channel and version, listener behavior, route filters, cross-namespace references and status conditions. Do not copy an example from another controller and assume it works unchanged.
Stage the migration
- Install or upgrade the controller in a test cluster.
- Create the GatewayClass and a non-production Gateway.
- Move one low-risk host into an HTTPRoute.
- Validate TLS, redirects, health checks and client IP handling.
- Compare response codes and latency against the Ingress path.
- Move traffic gradually and retain a rollback route.
Example HTTPRoute
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: app-route
spec:
parentRefs:
- name: public-gateway
hostnames: ["app.example.com"]
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- name: app-service
port: 8080
Use the manifest as a starting point and confirm the controller’s listener and namespace policies. Observe route status conditions and controller logs during rollout.
Migration pitfalls
Common failures include missing cross-namespace ReferenceGrants, mismatched TLS certificate references, controller-specific annotations that were not translated and DNS still pointing at the old load balancer. Document a rollback path before switching DNS.
Gateway API can improve ownership boundaries, but it does not remove the need for testing. Review reverse proxy fundamentals and Kubernetes DNS troubleshooting.
Engineering considerations
Inventory controller-specific behavior before translating manifests. Ingress controllers often rely on annotations for rewrites, authentication, rate limits, timeouts, body size and client IP handling. These settings are not automatically translated into Gateway API resources. Classify each annotation as portable, replaceable with a standard filter or dependent on a controller extension. Confirm the extension’s lifecycle and support commitment before making it part of a platform contract.
Implementation details
Define ownership boundaries explicitly. Platform teams can control listeners, allowed namespaces and TLS certificates, while application teams own HTTPRoute rules. Use allowedRoutes and ReferenceGrant policies to prevent an application team from exposing arbitrary hostnames or referencing privileged backends. Document who approves a public hostname, cross-namespace backend reference or new listener. The separation is useful only when the permission model is as clear as the resource model.
Security and reliability controls
Plan TLS termination and certificate lifecycle. Decide whether TLS ends at the Gateway or is re-encrypted to the backend. Check certificate references, secret namespaces, renewal automation and SNI behavior. A route can be accepted while clients still receive the wrong certificate if listener configuration or DNS points elsewhere. Test expiry and renewal events, multiple hostnames and backend certificate validation. Avoid copying private keys across namespaces when the controller supports a narrower reference model.
Testing strategy
Compare routing semantics in detail: path prefix and exact matches, header matching, redirects, rewrites, query handling and backend weights. Test trailing slashes, encoded characters and overlapping host rules. Confirm how the controller handles invalid or conflicting routes and whether status conditions explain the cause. Keep a test matrix for browser traffic, API clients, WebSockets and large uploads. A simple GET request does not exercise every proxy behavior.
Operational monitoring
Deploy the new controller and Gateway alongside the existing Ingress path. Move a low-risk internal service first, then a small external hostname. Validate DNS, health checks, access logs, real client IP, security headers and latency. For critical services, shift traffic gradually through a load balancer or controlled DNS strategy. Keep the old path functional until the new route passes an agreed observation window and dependent systems have been checked.
Failure diagnosis
Gateway and HTTPRoute status conditions provide control-plane feedback, but do not prove the application is healthy. Monitor listener readiness, route acceptance, backend health, connection errors, response codes and latency. Alert on routes that become detached or unresolved after a controller upgrade. Correlate controller events with application logs to distinguish routing configuration problems from unhealthy backend services.
Rollout and maintenance
Keep old Ingress manifests until migration is complete. Record DNS and load-balancer changes and define rollback triggers before cutover. Do not delete old resources immediately after a successful test; cached DNS and long-lived connections may still reach the previous path. Review Gateway API conformance and extension policies as controller versions change. Treat the migration as a platform change with owners, test evidence and an explicit decommission plan.
Operational handover
Before handing this capability to an operations team, document the configuration owner, supported versions, dependency map and escalation path. Include the commands or dashboard views needed to verify normal operation, along with the expected values and known limitations. Store configuration in version control, review changes through the normal deployment process and keep a tested rollback procedure. Schedule periodic reviews because upstream components, security requirements and workload patterns change. A short runbook should explain how to identify a failed component, what evidence to collect, which actions are safe to retry and when to escalate. Test that runbook during a maintenance exercise rather than waiting for an outage. Finally, measure the result against a baseline: reliability improvements should be visible in error rates, latency, resource consumption, recovery time or reduced manual work. This makes the implementation maintainable after the original developer has moved to another project.
Migration acceptance criteria
Write measurable acceptance criteria before changing DNS or load balancers. Include successful certificate validation for every hostname, correct redirects, expected client IP visibility, stable backend health, acceptable p95 latency and no unexpected 4xx or 5xx increase. Test both allowed and denied cross-namespace references so the new platform does not accidentally widen access. Validate WebSocket upgrades, streaming responses, large request bodies and connection draining. Record the controller version and Gateway API CRD version used during testing. If a required feature depends on an implementation-specific extension, document the owner and upgrade compatibility plan. A migration is complete only when the new route has passed the test matrix and the old path can be safely decommissioned.
