Use Cases

Gateway API covers a very wide range of use cases (which is both a strength and a weakness!). This page is emphatically not meant to be an exhaustive list of these use cases: rather, it is meant to provide some examples that can be helpful to demonstrate how the API can be used.

In all cases, it's very important to bear in mind the roles and personas used in Gateway API. The use cases presented here are deliberately described in terms of Ana, Chihiro, and Ian: they are the ones for whom the API must be usable. (It's also important to remember that even though these roles might be filled by the same person, especially in smaller organizations, they all have distinct concerns that we need to consider separately.)

The Use Cases

• Basic north/south use case
• Multiple applications behind a single Gateway
• Basic east/west use case -- experimental
• Gateway and mesh use case -- experimental

Basic north/south use case

Standard Channel in v0.8.0+

The north/south use case is fully supported by the Standard Channel in v0.8.0+.

Ana has created a microservice application which she wants to run in Kubernetes. Her application will be used by clients outside the cluster, and while Ana has created the application, setting up the cluster is not in her wheelhouse.

1. Ana goes to Chihiro to ask them to set up a cluster. Ana tells Chihiro that her clients will expect her APIs to be available using URLs rooted at https://ana.application.com/.

2. Chihiro goes to Ian and requests a cluster.

3. Ian provisions a cluster running a gateway controller with a GatewayClass resource named basic-gateway-class. The gateway controller manages the infrastructure associated with routing traffic from outside the cluster to inside the cluster.

4. Ian gives Chihiro credentials to the new cluster, and tells Chihiro that they can use GatewayClass basic-gateway-class to set things up.

5. Chihiro applies a Gateway named ana-gateway to the cluster, telling it to listen on port 443 for TLS traffic, and providing it a TLS certificate with a Subject CN of ana.application.com. They associate this Gateway with the basic-gateway-class GatewayClass.

6. The gateway controller that Ian provisioned in step 3 allocates a load balancer and an IP address for ana-gateway, provisions data-plane components that can route requests arriving at the load balancer on port 443, and starts watching for routing resources associated with ana-gateway.

7. Chihiro gets the IP address of ana-gateway and creates a DNS record outside the cluster for ana.application.com to match.

8. Chihiro tells Ana that she's good to go, using the Gateway named ana-gateway.

9. Ana writes and applies HTTPRoute resources to configure which URL paths are allowed and which microservices should handle them. She associates these HTTPRoutes with Gateway ana-gateway using the Gateway API Route Attachment Process.

10. At this point, when requests arrive at the load balancer, they are routed to Ana's application according to her routing specification.

This allows Chihiro to enforce centralized policies such as TLS at the Gateway, while simultaneously allowing Ana and her colleagues control over the application's routing logic and rollout plans (e.g. traffic splitting rollouts).

Multiple applications behind a single Gateway

Standard Channel in v0.8.0+

The north/south use case is fully supported by the Standard Channel in v0.8.0+.

This is remarkably similar to the basic north/south use case, but there are multiple application teams: Ana and her team are managing a storefront application in the store Namespace, while Allison and her team are managing a website in the site Namespace.

• Ian and Chihiro work together to provide a cluster, GatewayClass, and Gateway, as above.

• Ana and Allison independently deploy workloads and HTTPRoutes bound to the same Gateway resource.

Again, this separation of concerns allows Chihiro to enforce centralized policies such as TLS can be enforced at the Gateway. Meanwhile, Ana and Allison run their applications in their own Namespaces, but attach their Routes to the same shared Gateway, allowing them to independently control their routing logic, traffic splitting rollout, etc., while not worrying about the things that Chihiro and Ian are handling.

Basic east/west use case

Experimental in v0.8.0

The GAMMA initiative work for supporting service mesh use cases is experimental in v0.8.0. It is possible that it will change; we do not recommend it in production at this point.

In this scenario, Ana has built a workload which is already running in a cluster with a GAMMA-compliant service mesh. She wants to use the mesh to protect her workload by rejecting calls to her workload with incorrect URL paths, and by enforcing timeouts whenever anyone makes a request of her workload.

• Chihiro and Ian have already provided a cluster with a running service mesh. Ana doesn't need to make any requests of them.

• Ana writes an HTTPRoute that defines acceptable routes and timeouts and has a parentRef of her workload's Service.

• Ana applies her HTTPRoute in the same Namespace as her workload.

• The mesh automatically starts enforcing the routing policy described by Ana's HTTPRoute.

In this case, the separation of concerns across roles allows Ana to take advantage of the service mesh, with custom routing logic, without any bottlenecks in requests to Chihiro or Ian.

Gateway and mesh use case

Experimental in v0.8.0

The GAMMA initiative work for supporting service mesh use cases is experimental in v0.8.0. It is possible that it will change; we do not recommend it in production at this point.

This is effectively a combination of the multiple applications behind a single Gateway and basic east/west use cases:

• Chihiro and Ian will provision a cluster, a GatewayClass, and a Gateway.

• Ana and Allison will deploy their applications in the appropriate Namespaces.

• Ana and Allison will then apply HTTPRoute resources as appropriate.

There are two very important changes in this scenario, though, since a mesh is involved:

1. If Chihiro has deployed a gateway controller that defaults to Service routing, they will probably need to reconfigure it for endpoint routing. (This is an ongoing area of work for GAMMA, but the expectation is that endpoint routing will be recommended.)

2. Ana and/or Allison will need to bind HTTPRoutes to their respective workloads' Services to configure mesh routing logic. These could be distinct HTTPRoutes solely for the mesh, or they could apply single HTTPRoutes that bind to both the Gateway and a Service.

As always, the ultimate point of separating concerns in this way is that it permits Chihiro to enforce centralized policies such as TLS at the Gateway, while allowing Ana and Allison to retain independent control of routing logic, traffic splitting rollout, etc., both for north/south and for east/west routing.