Nameresolvers: add support for ResolveIDMulti (#3284)

Signed-off-by: ItalyPaleAle <43508+ItalyPaleAle@users.noreply.github.com>

nameresolution/kubernetes/kubernetes.go

@@ -16,7 +16,10 @@ package kubernetes
 import (
 	"bytes"
 	"context"
+	"fmt"
+	"net"
 	"strconv"
+	"strings"
 	"text/template"
 
 	"github.com/dapr/components-contrib/nameresolution"
@@ -30,6 +33,12 @@ const (
 	TemplateKey          = "template"
 )
 
+// Compile-time interface assertions
+var (
+	_ nameresolution.Resolver      = (*resolver)(nil)
+	_ nameresolution.ResolverMulti = (*resolver)(nil)
+)
+
 func executeTemplateWithResolveRequest(tmpl *template.Template, req nameresolution.ResolveRequest) (string, error) {
 	var addr bytes.Buffer
 	if err := tmpl.Execute(&addr, req); err != nil {
@@ -91,3 +100,33 @@ func (k *resolver) ResolveID(ctx context.Context, req nameresolution.ResolveRequ
 	// Dapr requires this formatting for Kubernetes services
 	return req.ID + "-dapr." + req.Namespace + ".svc." + k.clusterDomain + ":" + strconv.Itoa(req.Port), nil
 }
+
+// ResolveIDMulti resolves an app-id to a set of IP addresses in Kubernetes
+func (k *resolver) ResolveIDMulti(ctx context.Context, req nameresolution.ResolveRequest) (nameresolution.AddressList, error) {
+	// First, get the address from ResolveID, which is usually a DNS name
+	addr, err := k.ResolveID(ctx, req)
+	if err != nil {
+		return nil, err
+	}
+
+	// Extract the port if present
+	var port string
+	idx := strings.LastIndexByte(addr, ':')
+	if idx > -1 && (idx+1) < len(addr) {
+		port = addr[(idx + 1):]
+		addr = addr[:idx]
+	}
+
+	// Resolve the DNS name for a list of IPv4 or IPv6
+	ips, err := net.LookupIP(addr)
+	if err != nil {
+		return nil, fmt.Errorf("failed to resolve address for '%s': %w", addr, err)
+	}
+
+	// Return a list of IPs + port
+	res := make(nameresolution.AddressList, len(ips))
+	for i, ip := range ips {
+		res[i] = net.JoinHostPort(ip.String(), port)
+	}
+	return res, nil
+}

nameresolution/nameresolution.go

@@ -15,6 +15,8 @@ package nameresolution
 
 import (
 	"context"
+	"math/rand"
+	"strconv"
 )
 
 // Resolver is the interface of name resolver.
@@ -24,3 +26,39 @@ type Resolver interface {
 	// ResolveID resolves name to address.
 	ResolveID(ctx context.Context, req ResolveRequest) (string, error)
 }
+
+// ResolverMulti is an optional interface for name resolvers that can return multiple addresses.
+type ResolverMulti interface {
+	ResolveIDMulti(ctx context.Context, req ResolveRequest) (AddressList, error)
+}
+
+// ResolveRequest represents service discovery resolver request.
+type ResolveRequest struct {
+	ID        string
+	Namespace string
+	Port      int
+	Data      map[string]string
+}
+
+// CacheKey returns a string that can be used to identify this ResolveRequest in a cache
+func (r ResolveRequest) CacheKey() string {
+	return r.Namespace + "/" + r.ID + "/" + strconv.Itoa(r.Port)
+}
+
+// AddressList is a list of addresses resolved by the nameresolver
+type AddressList []string
+
+// Pick returns a random address from the list
+func (a AddressList) Pick() string {
+	l := len(a)
+	switch l {
+	case 0:
+		return ""
+	case 1:
+		return a[0]
+	default:
+		// We use math/rand here as we are just picking a random address, so we don't need a CSPRNG
+		//nolint:gosec
+		return a[rand.Intn(l)]
+	}
+}

nameresolution/requests.go

@@ -1,22 +0,0 @@
-/*
-Copyright 2021 The Dapr Authors
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-    http://www.apache.org/licenses/LICENSE-2.0
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-package nameresolution
-
-// ResolveRequest represents service discovery resolver request.
-type ResolveRequest struct {
-	ID        string
-	Namespace string
-	Port      int
-	Data      map[string]string
-}