plugin/clouddns: add refresh directive (#8616)

Brings clouddns to parity with route53, which already exposes a
refresh directive to control how often zones are re-synced. clouddns
currently hardcodes this to 1 minute (delay := 1 * time.Minute in Run)
with no way to change it.

Adds a refresh field to the CloudDNS struct, threads it through New(),
and has Run() use h.refresh instead of the hardcoded delay. Parses the
refresh directive in setup() mirroring route53's exact validation
(accepts a plain number as seconds or a duration string, must be
greater than 0).

Extends TestSetupCloudDNS with refresh coverage (valid duration, valid
plain number, missing arg, non-numeric, zero, negative). Verified it
fails without the setup.go change (unknown property error) and passes
with it.

Signed-off-by: stackedbyaradhya <aradhyaj736@gmail.com>

plugin/clouddns/README.md

@@ -21,6 +21,7 @@ the hosted zone.
 clouddns [ZONE:PROJECT_ID:HOSTED_ZONE_NAME...] {
     credentials [FILENAME]
     fallthrough [ZONES...]
+    refresh DURATION
 }
 ~~~
 
@@ -45,6 +46,12 @@ clouddns [ZONE:PROJECT_ID:HOSTED_ZONE_NAME...] {
     authoritative. If specific zones are listed (for example `in-addr.arpa` and `ip6.arpa`), then
     only queries for those zones will be subject to fallthrough.
 
+*   `refresh` can be used to control how long between record retrievals from Cloud DNS. It requires
+    a duration string as a parameter to specify the duration between update cycles. Each update
+    cycle may result in many Cloud DNS API calls depending on how many domains use this plugin and
+    how many records are in each. Adjusting the update frequency may help reduce the potential of
+    API throttling by Google Cloud. If not provided the default refresh is 1 minute.
+
 ## Examples
 
 Enable clouddns with implicit GCP credentials and resolve CNAMEs via 10.0.0.1:
@@ -73,3 +80,13 @@ Enable clouddns with multiple hosted zones with the same domain:
     clouddns example.org.:gcp-example-project:example-zone example.com.:gcp-example-project:other-example-zone
 }
 ~~~
+
+Enable clouddns and refresh records every 3 minutes:
+
+~~~ txt
+example.org {
+    clouddns example.org.:gcp-example-project:example-zone {
+        refresh 3m
+    }
+}
+~~~

plugin/clouddns/clouddns.go

@@ -28,6 +28,7 @@ type CloudDNS struct {
 	zoneNames []string
 	client    gcpDNS
 	upstream  *upstream.Upstream
+	refresh   time.Duration
 
 	zMu   sync.RWMutex
 	zones zones
@@ -46,8 +47,9 @@ type zones map[string][]*zone
 // string of project name and hosted zone name lists as its values, validates
 // that each domain name/zone id pair does exist, and returns a new *CloudDNS.
 // In addition to this, upstream is passed for doing recursive queries against CNAMEs.
+// refresh sets how often the zones are refreshed from Cloud DNS.
 // Returns error if it cannot verify any given domain name/zone id pair.
-func New(_ctx context.Context, c gcpDNS, keys map[string][]string, up *upstream.Upstream) (*CloudDNS, error) {
+func New(_ctx context.Context, c gcpDNS, keys map[string][]string, up *upstream.Upstream, refresh time.Duration) (*CloudDNS, error) {
 	zones := make(map[string][]*zone, len(keys))
 	zoneNames := make([]string, 0, len(keys))
 	for dnsName, hostedZoneDetails := range keys {
@@ -72,6 +74,7 @@ func New(_ctx context.Context, c gcpDNS, keys map[string][]string, up *upstream.
 		zoneNames: zoneNames,
 		zones:     zones,
 		upstream:  up,
+		refresh:   refresh,
 	}, nil
 }
 
@@ -82,11 +85,10 @@ func (h *CloudDNS) Run(ctx context.Context) error {
 		return err
 	}
 	go func() {
-		delay := 1 * time.Minute
+		timer := time.NewTimer(h.refresh)
-		timer := time.NewTimer(delay)
 		defer timer.Stop()
 		for {
-			timer.Reset(delay)
+			timer.Reset(h.refresh)
 			select {
 			case <-ctx.Done():
 				log.Debugf("Breaking out of CloudDNS update loop for %v: %v", h.zoneNames, ctx.Err())

plugin/clouddns/clouddns_test.go

@@ -6,6 +6,7 @@ import (
 	"reflect"
 	"sync"
 	"testing"
+	"time"
 
 	"github.com/coredns/coredns/plugin/file"
 	"github.com/coredns/coredns/plugin/pkg/dnstest"
@@ -134,7 +135,7 @@ func (c fakeGCPClient) listRRSets(_ctx context.Context, projectName, hostedZoneN
 func TestCloudDNS(t *testing.T) {
 	ctx := context.Background()
 
-	r, err := New(ctx, fakeGCPClient{}, map[string][]string{"bad.": {"bad-project:bad-zone"}}, &upstream.Upstream{})
+	r, err := New(ctx, fakeGCPClient{}, map[string][]string{"bad.": {"bad-project:bad-zone"}}, &upstream.Upstream{}, time.Minute)
 	if err != nil {
 		t.Fatalf("Failed to create Cloud DNS: %v", err)
 	}
@@ -142,7 +143,7 @@ func TestCloudDNS(t *testing.T) {
 		t.Fatalf("Expected errors for zone bad.")
 	}
 
-	r, err = New(ctx, fakeGCPClient{}, map[string][]string{"org.": {"sample-project-1:sample-zone-2", "sample-project-1:sample-zone-1"}, "gov.": {"sample-project-1:sample-zone-2", "sample-project-1:sample-zone-1"}}, &upstream.Upstream{})
+	r, err = New(ctx, fakeGCPClient{}, map[string][]string{"org.": {"sample-project-1:sample-zone-2", "sample-project-1:sample-zone-1"}, "gov.": {"sample-project-1:sample-zone-2", "sample-project-1:sample-zone-1"}}, &upstream.Upstream{}, time.Minute)
 	if err != nil {
 		t.Fatalf("Failed to create Cloud DNS: %v", err)
 	}
@@ -339,6 +340,7 @@ func TestCloudDNSConcurrentServeDNS(t *testing.T) {
 			"org.": {"sample-project-1:sample-zone-2", "sample-project-1:sample-zone-1"},
 		},
 		&upstream.Upstream{},
+		time.Minute,
 	)
 	if err != nil {
 		t.Fatalf("Failed to create Cloud DNS: %v", err)
@@ -406,7 +408,8 @@ func TestCloudDNSConcurrentLookupNameCache(t *testing.T) {
 		map[string][]string{
 			"org.": {"sample-project-1:sample-zone-2", "sample-project-1:sample-zone-1"},
 		},
-		&upstream.Upstream{})
+		&upstream.Upstream{},
+		time.Minute)
 	if err != nil {
 		t.Fatalf("Failed to create Cloud DNS: %v", err)
 	}

plugin/clouddns/setup.go

@@ -5,7 +5,9 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"strconv"
 	"strings"
+	"time"
 
 	"github.com/coredns/caddy"
 	"github.com/coredns/coredns/core/dnsserver"
@@ -64,6 +66,7 @@ func setup(c *caddy.Controller) error {
 		}
 
 		var opt option.ClientOption
+		refresh := time.Duration(1) * time.Minute // default update frequency to 1 minute
 		for c.NextBlock() {
 			switch c.Val() {
 			case "upstream":
@@ -79,6 +82,22 @@ func setup(c *caddy.Controller) error {
 				opt = option.WithAuthCredentialsFile(credType, c.Val())
 			case "fallthrough":
 				fall.SetZonesFromArgs(c.RemainingArgs())
+			case "refresh":
+				if !c.NextArg() {
+					return plugin.Error("clouddns", c.ArgErr())
+				}
+				refreshStr := c.Val()
+				_, err := strconv.Atoi(refreshStr)
+				if err == nil {
+					refreshStr += "s"
+				}
+				refresh, err = time.ParseDuration(refreshStr)
+				if err != nil {
+					return plugin.Error("clouddns", c.Errf("unable to parse duration: %v", err))
+				}
+				if refresh <= 0 {
+					return plugin.Error("clouddns", c.Errf("refresh interval must be greater than 0: %q", refreshStr))
+				}
 			default:
 				return plugin.Error("clouddns", c.Errf("unknown property %q", c.Val()))
 			}
@@ -91,7 +110,7 @@ func setup(c *caddy.Controller) error {
 			return err
 		}
 
-		h, err := New(ctx, client, keys, up)
+		h, err := New(ctx, client, keys, up, refresh)
 		if err != nil {
 			cancel()
 			return plugin.Error("clouddns", c.Errf("failed to create plugin: %v", err))

plugin/clouddns/setup_test.go

@@ -55,6 +55,24 @@ func TestSetupCloudDNS(t *testing.T) {
 }`, false},
 		{`clouddns example.org.:example-project:zone-name {
     credentials
+}`, true},
+		{`clouddns example.org.:example-project:zone-name {
+    refresh 3m
+}`, false},
+		{`clouddns example.org.:example-project:zone-name {
+    refresh 30
+}`, false},
+		{`clouddns example.org.:example-project:zone-name {
+    refresh
+}`, true},
+		{`clouddns example.org.:example-project:zone-name {
+    refresh abc
+}`, true},
+		{`clouddns example.org.:example-project:zone-name {
+    refresh 0
+}`, true},
+		{`clouddns example.org.:example-project:zone-name {
+    refresh -5m
 }`, true},
 		{`clouddns example.org.:example-project:zone-name example.org.:example-project:zone-name {
 	}`, true},