feat(Google CloudDNS): add routing policy support

docs/tutorials/google.md

@@ -0,0 +1,54 @@
+## Annotations
+
+Annotations which are specific to the Google
+[CloudDNS](https://cloud.google.com/dns/docs/overview) provider.
+
+### Routing Policy
+
+The [routing policy](https://cloud.google.com/dns/docs/routing-policies-overview)
+for resource record sets managed by ExternalDNS may be specified by applying the
+`external-dns.alpha.kubernetes.io/google-routing-policy` annotation on any of the
+supported [sources](../sources/about.md).
+
+#### Geolocation routing policies
+
+Specifying a value of `geo` for the `external-dns.alpha.kubernetes.io/google-routing-policy`
+annotation will enable geolocation routing for associated resource record sets. The
+location attributed to resource record sets may be deduced for instances of ExternalDNS
+running within the Google Cloud platform or may be specified via the `--google-location`
+command-line argument. Alternatively, a location may be explicitly specified via the
+`external-dns.alpha.kubernetes.io/google-location` annotation, where the value is one
+of Google Cloud's [locations/regions](https://cloud.google.com/docs/geography-and-regions).
+
+For example:
+```yaml
+apiVersion: externaldns.k8s.io/v1alpha1
+kind: DNSEndpoint
+metadata:
+  name: geo-example
+  annotations:
+    external-dns.alpha.kubernetes.io/google-routing-policy: "geo"
+    external-dns.alpha.kubernetes.io/google-location: "us-east1"
+```
+
+#### Weighted Round Robin routing policies
+
+Specifying a value of `wrr` for the `external-dns.alpha.kubernetes.io/google-routing-policy`
+annotation will enable weighted round-robin routing for associated resource record sets.
+The weight to be attributed to resource record sets may be specified via the
+`external-dns.alpha.kubernetes.io/google-weight` annotation, where the value is a string
+representation of a floating-point number. The `external-dns.alpha.kubernetes.io/set-identifier`
+annotation must also be applied providing a string value representation of an index into
+the list of potential responses.
+
+For example:
+```yaml
+apiVersion: externaldns.k8s.io/v1alpha1
+kind: DNSEndpoint
+metadata:
+  name: wrr-example
+  annotations:
+    external-dns.alpha.kubernetes.io/google-routing-policy: "wrr"
+    external-dns.alpha.kubernetes.io/google-weight: "100.0"
+    external-dns.alpha.kubernetes.io/set-identifier: "0"
+```

main.go

@@ -248,7 +248,7 @@ func main() {
 	case "cloudflare":
 		p, err = cloudflare.NewCloudFlareProvider(domainFilter, zoneIDFilter, cfg.CloudflareProxied, cfg.DryRun, cfg.CloudflareDNSRecordsPerPage, cfg.CloudflareRegionKey)
 	case "google":
-		p, err = google.NewGoogleProvider(ctx, cfg.GoogleProject, domainFilter, zoneIDFilter, cfg.GoogleBatchChangeSize, cfg.GoogleBatchChangeInterval, cfg.GoogleZoneVisibility, cfg.DryRun)
+		p, err = google.NewGoogleProvider(ctx, cfg.GoogleProject, cfg.GoogleLocation, domainFilter, zoneIDFilter, cfg.GoogleBatchChangeSize, cfg.GoogleBatchChangeInterval, cfg.GoogleZoneVisibility, cfg.DryRun)
 	case "digitalocean":
 		p, err = digitalocean.NewDigitalOceanProvider(ctx, domainFilter, cfg.DryRun, cfg.DigitalOceanAPIPageSize)
 	case "ovh":

pkg/apis/externaldns/types.go

@@ -69,6 +69,7 @@ type Config struct {
 	Provider                           string
 	ProviderCacheTime                  time.Duration
 	GoogleProject                      string
+	GoogleLocation                     string
 	GoogleBatchChangeSize              int
 	GoogleBatchChangeInterval          time.Duration
 	GoogleZoneVisibility               string
@@ -234,6 +235,7 @@ var defaultConfig = &Config{
 	Provider:                    "",
 	ProviderCacheTime:           0,
 	GoogleProject:               "",
+	GoogleLocation:              "",
 	GoogleBatchChangeSize:       1000,
 	GoogleBatchChangeInterval:   time.Second,
 	GoogleZoneVisibility:        "",
@@ -463,6 +465,7 @@ func (cfg *Config) ParseFlags(args []string) error {
 	app.Flag("zone-name-filter", "Filter target zones by zone domain (For now, only AzureDNS provider is using this flag); specify multiple times for multiple zones (optional)").Default("").StringsVar(&cfg.ZoneNameFilter)
 	app.Flag("zone-id-filter", "Filter target zones by hosted zone id; specify multiple times for multiple zones (optional)").Default("").StringsVar(&cfg.ZoneIDFilter)
 	app.Flag("google-project", "When using the Google provider, current project is auto-detected, when running on GCP. Specify other project with this. Must be specified when running outside GCP.").Default(defaultConfig.GoogleProject).StringVar(&cfg.GoogleProject)
+	app.Flag("google-location", "When using the Google provider, current location is auto-detected, when running on GCP. Specify location with this. May be specified when running outside GCP.").Default(defaultConfig.GoogleLocation).StringVar(&cfg.GoogleLocation)
 	app.Flag("google-batch-change-size", "When using the Google provider, set the maximum number of changes that will be applied in each batch.").Default(strconv.Itoa(defaultConfig.GoogleBatchChangeSize)).IntVar(&cfg.GoogleBatchChangeSize)
 	app.Flag("google-batch-change-interval", "When using the Google provider, set the interval between batch changes.").Default(defaultConfig.GoogleBatchChangeInterval.String()).DurationVar(&cfg.GoogleBatchChangeInterval)
 	app.Flag("google-zone-visibility", "When using the Google provider, filter for zones with this visibility (optional, options: public, private)").Default(defaultConfig.GoogleZoneVisibility).EnumVar(&cfg.GoogleZoneVisibility, "", "public", "private")

pkg/apis/externaldns/types_test.go

@@ -43,6 +43,7 @@ var (
 		Compatibility:               "",
 		Provider:                    "google",
 		GoogleProject:               "",
+		GoogleLocation:              "",
 		GoogleBatchChangeSize:       1000,
 		GoogleBatchChangeInterval:   time.Second,
 		GoogleZoneVisibility:        "",
@@ -142,6 +143,7 @@ var (
 		Compatibility:               "mate",
 		Provider:                    "google",
 		GoogleProject:               "project",
+		GoogleLocation:              "location",
 		GoogleBatchChangeSize:       100,
 		GoogleBatchChangeInterval:   time.Second * 2,
 		GoogleZoneVisibility:        "private",
@@ -271,6 +273,7 @@ func TestParseFlags(t *testing.T) {
 				"--compatibility=mate",
 				"--provider=google",
 				"--google-project=project",
+				"--google-location=location",
 				"--google-batch-change-size=100",
 				"--google-batch-change-interval=2s",
 				"--google-zone-visibility=private",
@@ -391,6 +394,7 @@ func TestParseFlags(t *testing.T) {
 				"EXTERNAL_DNS_COMPATIBILITY":                   "mate",
 				"EXTERNAL_DNS_PROVIDER":                        "google",
 				"EXTERNAL_DNS_GOOGLE_PROJECT":                  "project",
+				"EXTERNAL_DNS_GOOGLE_LOCATION":                 "location",
 				"EXTERNAL_DNS_GOOGLE_BATCH_CHANGE_SIZE":        "100",
 				"EXTERNAL_DNS_GOOGLE_BATCH_CHANGE_INTERVAL":    "2s",
 				"EXTERNAL_DNS_GOOGLE_ZONE_VISIBILITY":          "private",

plan/plan.go

@@ -18,6 +18,8 @@ package plan
 
 import (
 	"fmt"
+	"iter"
+	"maps"
 	"strings"
 
 	"github.com/google/go-cmp/cmp"
@@ -51,6 +53,39 @@ type Plan struct {
 	OwnerID string
 }
 
+// RRName is a canonical name associated with a resource record (i.e. lower-case with trailing period)
+type RRName string
+
+// RRType is a type associated with a resource record (e.g., "A", "AAAA", "TXT", etc.)
+type RRType string
+
+// RRKey is a key for entries in maps of resource records
+type RRKey struct {
+	Name RRName
+	Type RRType
+}
+
+func newRRKey(ep *endpoint.Endpoint) RRKey {
+	return RRKey{
+		Name: RRName(normalizeDNSName(ep.DNSName)),
+		Type: RRType(ep.RecordType),
+	}
+}
+
+// RRSetChange represents changes to be applied to a single resource record set
+//
+// | Action | Create | Delete |
+// |--------+--------+--------|
+// | Create |   *    |  nil   |
+// | Delete |  nil   |   *    |
+// | Update |   *    |   *    |
+type RRSetChange struct {
+	Name   RRName
+	Type   RRType
+	Create []*endpoint.Endpoint
+	Delete []*endpoint.Endpoint
+}
+
 // Changes holds lists of actions to be executed by dns providers
 type Changes struct {
 	// Records that need to be created
@@ -154,6 +189,63 @@ func (t *planTable) newPlanKey(e *endpoint.Endpoint) planKey {
 	return key
 }
 
+// Return an iterator of changes to resource records sets
+func (c *Changes) All() iter.Seq[*RRSetChange] {
+	return func(yield func(change *RRSetChange) bool) {
+		rrSetCreates := map[RRKey]*RRSetChange{}
+		rrSetDeletes := map[RRKey]*RRSetChange{}
+		rrSetUpdates := map[RRKey]*RRSetChange{}
+		for _, action := range []struct {
+			endpoints    *[]*endpoint.Endpoint
+			rrSetChanges *map[RRKey]*RRSetChange
+		}{
+			{endpoints: &c.UpdateNew, rrSetChanges: &rrSetUpdates},
+			{endpoints: &c.UpdateOld, rrSetChanges: &rrSetUpdates},
+			{endpoints: &c.Create, rrSetChanges: &rrSetCreates},
+			{endpoints: &c.Delete, rrSetChanges: &rrSetDeletes},
+		} {
+			for _, ep := range *action.endpoints {
+				rrKey := newRRKey(ep)
+				change, ok := rrSetUpdates[rrKey]
+				if !ok && action.rrSetChanges != &rrSetUpdates {
+					if action.rrSetChanges != &rrSetCreates {
+						change, ok = rrSetCreates[rrKey]
+						if ok {
+							delete(rrSetCreates, rrKey)
+							rrSetUpdates[rrKey] = change
+						}
+					}
+					if !ok {
+						change, ok = (*action.rrSetChanges)[rrKey]
+					}
+				}
+				if !ok {
+					change = &RRSetChange{
+						Name: rrKey.Name,
+						Type: rrKey.Type,
+					}
+					(*action.rrSetChanges)[rrKey] = change
+				}
+				switch action.endpoints {
+				case &c.Create, &c.UpdateNew:
+					change.Create = append(change.Create, ep)
+				case &c.Delete, &c.UpdateOld:
+					change.Delete = append(change.Delete, ep)
+				}
+			}
+		}
+		for _, rrSetChanges := range []*map[RRKey]*RRSetChange{
+			&rrSetDeletes, &rrSetUpdates, &rrSetCreates,
+		} {
+			for rrSetChange := range maps.Values(*rrSetChanges) {
+				if !yield(rrSetChange) {
+					return
+				}
+			}
+		}
+	}
+}
+
 func (c *Changes) HasChanges() bool {
 	if len(c.Create) > 0 || len(c.Delete) > 0 {
 		return true