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Request Routing

Incoming requests to Kusk Gateway can be routed to the target service in two ways:

  • Forwarded to an actual service in your cluster using the upstream property.
  • Redirected to a different endpoint using the redirect property.

Furthermore, two properties are available to distinguish to which of these an incoming request should go:

  • The hosts property allows you to define to which hostname(s) a specific API answers.
  • The path property allows you to configure a base path for the exposed API.

Any of these properties can be specified at the root, path, or operation level in your OpenAPI definition, allowing you to route separate operations differently. For example, not all operations might be handled by the same service, in which case you could define different upstream services accordingly.

Forwarding Requests to a Service in your Cluster

This will be the most common scenario - incoming requests to Kusk Gateway will be forward to a service or host running in your cluster:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  upstream:
    service:
      name: simple-api-service
      namespace: default
..

Here all requests are sent to the simple-api-service in the default namespace on the default port (80).

If we had a different service for one of the operations, we could override this at the operation level:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  upstream:
    service: 
      name: simple-api-service
      namespace: default
      port: 8001
path:
  /someoperation:
    get:
      operationId: doSomething
      x-kusk:
        upstream:
          service:
            name: another-service
            port: 8080
..

Here the default service is listening on port 8001 and we have specified a different service for the doSomething operation, still in the same namespace but also on a different port.

If we instead wanted to route default API requests to different hostname, instead of a specific service, we could do something like:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  upstream:
    host:
      hostname: simple-api-service-hostname
      port: 8001
..

Also, we could override this routing at the operation level as before:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  upstream:
    host:
      hostname: simple-api-service-hostname
      port: 8001
path:
  /someoperation:
    get:
      operationId: doSomething
      x-kusk:
        upstream:
          service:
            name: another-service
            port: 8080
..

Rewriting Request Paths

The optional rewrite property allows us to modify the path of the request before forwarding it to the upstream service. For example, if we have a service foo with a single endpoint /bar, we configure Kusk Gateway to forward traffic to the foo service when it receives traffic on a path with the prefix /foo.

path rewrite example

If we receive a request at /foo/bar, the request will be forwarded to the foo service. foo will throw a 404 error as it doesn't have a path /foo/bar.

Therefore, we must rewrite the path from /foo/bar to /bar before sending it onto the foo service.

The following config extract will allow us to do this:

upstream:
  service: 
    ...
  # /foo/bar/... -> to upstream: /bar/...
  rewrite:
    pattern: "^/foo"
    substitution: ""

See all available upstream configuration options in the Extension Reference.

Redirecting Requests to a Different Host/Path

Instead of forwarding requests to a service or hostname in our cluster, we might want to redirect the client to a totally different URL, for example, when:

  • The API has moved to a different host.
  • Individual operations have been renamed.

The redirect property allows us to do this. First, redirect to a different host:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  redirect:
    scheme_redirect: https
    host_redirect: thenewhost.com
    response_code: 302
..

This would redirect any requests to the API to the specified host using a 302 HTTP response.

As indicated above we could use this property to redirect individual operations:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  upstream:
    host: simple-api-service-hostname
    port: 8001
path:
  /newoperation:
    get:
      operationId: doSomething
      ..
  /oldoperation:
      x-kusk:
        redirect:
          path_redirect: /newoperation
..

This can be helpful when operations have been renamed during a major version update or if we want to deprecate an operation:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  upstream:
    host:
      hostname: simple-api-service-hostname
      port: 8001
path:
  /someoperation:
    get:
      operationId: doSomething
      ..
    put:
      x-kusk:
        redirect:
          scheme_redirect: https
          host_redirect: mywebsite.com
          path_redirect: /deprecated.html
..

See all available redirect configuration options in the Extension Reference.

Specifying an External Path for Your API

Often you will want to prefix your API path with something like "/api" externally, although your internal API implementation is running on the root path "/". Kusk allows you to specify a path property for this, which you can use together with the rewrite described above in this scenario:

x-kusk:
  path: /api
  upstream:
    service: 
      ...
    # /api/bar/... -> to upstream: /bar/...
    rewrite:
      pattern: "^/api"
      substitution: ""

Using Hosts for Multi-hosting Scenarios

In a multi-hosting scenario for a single IP, you might want to ensure that requests to different hosts go to different APIs:

  • https://onehost.com/api -> api nr 1
  • https://anotherhost.com/api -> api nr 2

You can use the hosts property for this:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  upstream:
    service: simple-api-service
    namespace: default
  hosts:
     - onehost.com
..

Now, only requests to the onehost.com host will get forward to the simple-api-service.

Disabling Operations

In certain situations, your OpenAPI definition might contain operations that you do not want exposed to API consumers, for example, if these are still in development or if they are meant to be consumed internally only. Kusk Gateway provides a x-kusk.disabled property for this purpose, which can be set at the global, path or operation level.

For example, if we wanted to disable the PUT operation in one of our examples above we could add this extension:

openapi: 3.0.0
info:
  title: simple-api
  version: 0.1.0
x-kusk:
  upstream:
    host:
      hostname: simple-api-service-hostname
      port: 8001
path:
  /someoperation:
    get:
      operationId: doSomething
      ..
    put:
      x-kusk:
        disabled: true

Setting this property to true at the top level will hide all operations, allowing you to override this property at the path or operation level when you want to expose only specific operations.