use kuberesolver for kubernetes service endpoints

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

Author: butonic

changelog/unreleased/respect-service-transport.md

@@ -1,5 +1,5 @@
 Enhancement: Respect service transport
 
-The service registry now takes into account the service transport when creating grpc clients. This allows using `dns` and `unix` as the protocol in addition to `tcp`. `dns` will turn the gRPC client into a [Thick Client](https://grpc.io/blog/grpc-load-balancing/#thick-client) that can look up multiple endpoints via DNS. Furthermore, we enabled round robin load balancing for the [default transparent retry configuration of gRPC](https://grpc.io/docs/guides/retry/#retry-configuration).
+The service registry now takes into account the service transport when creating grpc clients. This allows using `dns`, `unix` and `kubernetes` as the protocol in addition to `tcp`. `dns` will turn the gRPC client into a [Thick Client](https://grpc.io/blog/grpc-load-balancing/#thick-client) that can look up multiple endpoints via DNS. `kubernetes` will use [github.com/sercand/kuberesolver](https://github.com/sercand/kuberesolver) to connect to the kubernetes API and pickh up service changes. Furthermore, we enabled round robin load balancing for the [default transparent retry configuration of gRPC](https://grpc.io/docs/guides/retry/#retry-configuration).
 
 https://github.com/cs3org/reva/pull/4744

go.mod

@@ -71,6 +71,7 @@ require (
 	github.com/rs/cors v1.10.1
 	github.com/rs/zerolog v1.32.0
 	github.com/segmentio/kafka-go v0.4.47
+	github.com/sercand/kuberesolver/v5 v5.1.1
 	github.com/sethvargo/go-password v0.2.0
 	github.com/shamaton/msgpack/v2 v2.1.1
 	github.com/shirou/gopsutil v3.21.11+incompatible

go.sum

@@ -1566,6 +1566,8 @@ github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529 h1:nn5Wsu0esKSJiIVhscUt
 github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529/go.mod h1:DxrIzT+xaE7yg65j358z/aeFdxmN0P9QXhEzd20vsDc=
 github.com/segmentio/kafka-go v0.4.47 h1:IqziR4pA3vrZq7YdRxaT3w1/5fvIH5qpCwstUanQQB0=
 github.com/segmentio/kafka-go v0.4.47/go.mod h1:HjF6XbOKh0Pjlkr5GVZxt6CsjjwnmhVOfURM5KMd8qg=
+github.com/sercand/kuberesolver/v5 v5.1.1 h1:CYH+d67G0sGBj7q5wLK61yzqJJ8gLLC8aeprPTHb6yY=
+github.com/sercand/kuberesolver/v5 v5.1.1/go.mod h1:Fs1KbKhVRnB2aDWN12NjKCB+RgYMWZJ294T3BtmVCpQ=
 github.com/sergi/go-diff v1.1.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
 github.com/sergi/go-diff v1.2.0 h1:XU+rvMAioB0UC3q1MFrIQy4Vo5/4VsRDQQXHsEya6xQ=
 github.com/sergi/go-diff v1.2.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=

pkg/rgrpc/todo/pool/selector.go

@@ -44,9 +44,16 @@ import (
 	tx "github.com/cs3org/go-cs3apis/cs3/tx/v1beta1"
 	"github.com/cs3org/reva/v2/pkg/registry"
 	"github.com/pkg/errors"
+	"github.com/sercand/kuberesolver/v5"
 	"google.golang.org/grpc"
 )
 
+func init() {
+	// grpc go resolver.Register must only be called during initialization time (i.e. in
+	// an init() function), and is not thread-safe.
+	kuberesolver.RegisterInCluster()
+}
+
 type Selectable[T any] interface {
 	Next(opts ...Option) (T, error)
 }
@@ -97,7 +104,7 @@ func (s *Selector[T]) Next(opts ...Option) (T, error) {
 	target := s.id
 	prefix := strings.SplitN(s.id, ":", 2)[0]
 	switch prefix {
-	case "dns", "unix":
+	case "dns", "unix", "kubernetes":
 		// use target as is
 	default:
 		// use service registry to look up address