provider=google: Add Ttl from annotations:

Use `int64(ep.RecordTTL)` in `newRecord()`
Fallback to hardcoded 300s for backwards-compat
Add `TestNewRecords()`
Add notes in *ttl.md*

CHANGELOG.md

@@ -1,3 +1,5 @@
+  - Google: Support configuring TTL by annotation: `external-dns.alpha.kubernetes.io/ttl`. (#389) @stealthybox
+
 ## v0.4.8 - 2017-11-09
 
   - AWS: Added change batch limiting to a maximum of 4000 Route53 updates in one API call.  Changes exceeding the limit will be dropped but all related changes by hostname are preserved within the limit. (#368) @bitvector2

docs/ttl.md

@@ -24,7 +24,23 @@ Providers
 - [ ] Azure
 - [ ] Cloudflare
 - [ ] DigitalOcean
-- [ ] Google
+- [x] Google
 - [ ] InMemory
 
 PRs welcome!
+
+Notes
+=====
+When the `external-dns.alpha.kubernetes.io/ttl` annotation is not provided, the Ttl will default to 0 seconds and `enpoint.TTL.isConfigured()` will be false.
+
+### AWS Provider
+The AWS Provider overrides the value to 300s when the Ttl is 0. 
+This value is a constant in the provider code.
+
+### Google Provider
+Previously with the Google Provider, Ttl's were hard-coded to 300s.
+For safety, the Google Provider overrides the value to 300s when the Ttl is 0. 
+This value is a constant in the provider code.
+
+For the moment, it is impossible to use a Ttl value of 0 with the AWS and Google Providers.
+This behavior may change in the future.

provider/google.go

@@ -33,6 +33,10 @@ import (
 	"github.com/kubernetes-incubator/external-dns/plan"
 )
 
+const (
+	googleRecordTTL = 300
+)
+
 type managedZonesCreateCallInterface interface {
 	Do(opts ...googleapi.CallOption) (*dns.ManagedZone, error)
 }
@@ -319,10 +323,16 @@ func newRecord(ep *endpoint.Endpoint) *dns.ResourceRecordSet {
 		target = ensureTrailingDot(target)
 	}
 
+	// no annotation results in a Ttl of 0, default to 300 for backwards-compatability
+	var ttl int64 = googleRecordTTL
+	if ep.RecordTTL.IsConfigured() {
+		ttl = int64(ep.RecordTTL)
+	}
+
 	return &dns.ResourceRecordSet{
 		Name:    ensureTrailingDot(ep.DNSName),
 		Rrdatas: []string{target},
-		Ttl:     300,
+		Ttl:     ttl,
 		Type:    ep.RecordType,
 	}
 }

provider/google_test.go

@@ -398,6 +398,27 @@ func TestGoogleApplyChangesEmpty(t *testing.T) {
 	assert.NoError(t, provider.ApplyChanges(&plan.Changes{}))
 }
 
+func TestNewRecords(t *testing.T) {
+	records := newRecords([]*endpoint.Endpoint{
+		endpoint.NewEndpointWithTTL("update-test.zone-2.ext-dns-test-2.gcp.zalan.do", "8.8.4.4", endpoint.RecordTypeA, 1),
+		endpoint.NewEndpointWithTTL("delete-test.zone-2.ext-dns-test-2.gcp.zalan.do", "8.8.4.4", endpoint.RecordTypeA, 120),
+		endpoint.NewEndpointWithTTL("update-test-cname.zone-1.ext-dns-test-2.gcp.zalan.do", "bar.elb.amazonaws.com", endpoint.RecordTypeCNAME, 4000),
+		// test fallback to Ttl:300 when Ttl==0 :
+		endpoint.NewEndpointWithTTL("update-test.zone-1.ext-dns-test-2.gcp.zalan.do", "8.8.8.8", endpoint.RecordTypeA, 0),
+		endpoint.NewEndpoint("delete-test.zone-1.ext-dns-test-2.gcp.zalan.do", "8.8.8.8", endpoint.RecordTypeA),
+		endpoint.NewEndpoint("delete-test-cname.zone-1.ext-dns-test-2.gcp.zalan.do", "qux.elb.amazonaws.com", endpoint.RecordTypeCNAME),
+	})
+
+	validateChangeRecords(t, records, []*dns.ResourceRecordSet{
+		{Name: "update-test.zone-2.ext-dns-test-2.gcp.zalan.do.", Rrdatas: []string{"8.8.4.4"}, Type: "A", Ttl: 1},
+		{Name: "delete-test.zone-2.ext-dns-test-2.gcp.zalan.do.", Rrdatas: []string{"8.8.4.4"}, Type: "A", Ttl: 120},
+		{Name: "update-test-cname.zone-1.ext-dns-test-2.gcp.zalan.do.", Rrdatas: []string{"bar.elb.amazonaws.com."}, Type: "CNAME", Ttl: 4000},
+		{Name: "update-test.zone-1.ext-dns-test-2.gcp.zalan.do.", Rrdatas: []string{"8.8.8.8"}, Type: "A", Ttl: 300},
+		{Name: "delete-test.zone-1.ext-dns-test-2.gcp.zalan.do.", Rrdatas: []string{"8.8.8.8"}, Type: "A", Ttl: 300},
+		{Name: "delete-test-cname.zone-1.ext-dns-test-2.gcp.zalan.do.", Rrdatas: []string{"qux.elb.amazonaws.com."}, Type: "CNAME", Ttl: 300},
+	})
+}
+
 func TestSeparateChanges(t *testing.T) {
 	change := &dns.Change{
 		Additions: []*dns.ResourceRecordSet{
@@ -475,7 +496,9 @@ func validateChangeRecords(t *testing.T, records []*dns.ResourceRecordSet, expec
 
 func validateChangeRecord(t *testing.T, record *dns.ResourceRecordSet, expected *dns.ResourceRecordSet) {
 	assert.Equal(t, expected.Name, record.Name)
+	assert.Equal(t, expected.Rrdatas, record.Rrdatas)
 	assert.Equal(t, expected.Ttl, record.Ttl)
+	assert.Equal(t, expected.Type, record.Type)
 }
 
 func newGoogleProvider(t *testing.T, domainFilter DomainFilter, dryRun bool, records []*endpoint.Endpoint) *GoogleProvider {