gateway-api-controller

README

gateway-api-controller

This is an initial implementation of the various controllers required in order to manage Gateway API network deployments within Kubernetes. At the moment four basic controllers are implemented:

• GatewayClass
• Gateway
• TCPRoute
• UDPRoute

Usage

Build

go build

If I ever really learn how makefiles work, then perhaps i'll implement one

Running

If you're running outside of a Kubernetes cluster then something like the following will work..

./gateway-api-controller -metrics-bind-address :8083 -kubeconfig ~/.kube/config

Want to change the gatewayClass then the flag -gateway-class-name will probably help, setting the -ipam-configmap will point to a configmap that contains the range or cidr used for IPAM.

Create that range with the following:

kubectl create configmap --namespace default <configmap_name> --from-literal range-global=172.18.100.10-172.18.100.30

Example

The /manifests folder contains the basics of the GatewayClass, Gateway and TCPRoute yaml structure..

Implemented logic

• Currently the GatewayClass will set the status ACCEPTED -> True if the gateway controller matches the flag -gateway-class-name
• When a Gateway is created it will verify that the parent GatewayClass exists.
• The Gateway will also perform IPAM and apply an address to the .Spec.Address and .Status.Address fields
• The TCPRoute will look up its parent gateway and confirm that the it's the correct reference, it will then find the listener (external IP address)... with the listener and TCPRoute routes it will then lookup the referenced service.

Services implementation (WIP)

When creating a TCPRoute you can apply the following labels:

metadata:
  labels:
    selectorkey: app
    selectorvalue: my-nginx
    serviceBehaviour: create

The selector key/value is used when creating/updating/duplicating a corresponding service, the serviceBehaviour determins what the TCPRoute controller will do when a new route is created. (The default behaviour is to create a new service, referenced by rules.backendRefs.name)

Thoughts

As Gateway-API has no concept of selectors (to identify a range of pods or endpoints), it refers to a a service though the []rules.[]backendRefs.name (multiple rules, with multiple backends) with a destination port and destination service (identified as name). With L2/L3 loadbalancers not touching the dataplane we rely in Kubernetes services (of type=LoadBalancer) to configure the kube-proxy so that the dataplane works, without selectors we can't create "enough" of a new service that will map to endpoints.. we can refer to an existing service (that a user has to create) however.

So what are the options moving forward:

Idea 1

Add key/value labels to a TCPRoute that "emulate" the selector on a service, we can then create a brand new service of type=LoadBalancer with the external address from the gateway and the destination settings of the TCPRoute.

Idea 2

We can ask a user to create a quick service (clusterIP etc..) that has the selectors in it, we can then duplicate that service with type=LoadBalancer and set the .spec.LoadBalancerIP from the gateway address along with the additional config from the TCPRoute.

Idea 3

We can update the refered service with the configuration from the gateway/TCPRoute so that it behaves as we're asking Gateway API.

It will create a new service based upon that referenced service with the type loadbalancer and away we go...

that's it so far (clearly a long way to go)

Want to Contribute?

Please and thankyou