From d3139cf2efbb99c70398e52d7b03c89507b6c942 Mon Sep 17 00:00:00 2001
From: Gaurav Ghildiyal <gauravkg@google.com>
Date: Mon, 27 Mar 2023 15:16:38 -0700
Subject: [PATCH] Use Patch when syncing GCP BackendService. Linking backend
 groups still uses Update

---
 pkg/backends/backends.go    | 19 +++++++++++++++++++
 pkg/backends/interfaces.go  |  2 ++
 pkg/backends/syncer.go      |  5 ++++-
 pkg/backends/syncer_test.go |  3 +++
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/pkg/backends/backends.go b/pkg/backends/backends.go
index 4a00e62760..3534d57fbd 100644
--- a/pkg/backends/backends.go
+++ b/pkg/backends/backends.go
@@ -129,6 +129,25 @@ func (b *Backends) Update(be *composite.BackendService) error {
 	return nil
 }
 
+// Patch implements Pool.
+func (b *Backends) Patch(be *composite.BackendService) error {
+	// Ensure the backend service has the proper version before updating.
+	be.Version = features.VersionFromDescription(be.Description)
+	scope, err := composite.ScopeFromSelfLink(be.SelfLink)
+	if err != nil {
+		return err
+	}
+
+	key, err := composite.CreateKey(b.cloud, be.Name, scope)
+	if err != nil {
+		return err
+	}
+	if err := composite.PatchBackendService(b.cloud, key, be); err != nil {
+		return err
+	}
+	return nil
+}
+
 // Get implements Pool.
 func (b *Backends) Get(name string, version meta.Version, scope meta.KeyType) (*composite.BackendService, error) {
 	key, err := composite.CreateKey(b.cloud, name, scope)
diff --git a/pkg/backends/interfaces.go b/pkg/backends/interfaces.go
index f8f20ab2f0..57826bc5bf 100644
--- a/pkg/backends/interfaces.go
+++ b/pkg/backends/interfaces.go
@@ -39,6 +39,8 @@ type Pool interface {
 	Create(sp utils.ServicePort, hcLink string) (*composite.BackendService, error)
 	// Update a BackendService given the composite type.
 	Update(be *composite.BackendService) error
+	// Patch a BackendService given the composite type.
+	Patch(be *composite.BackendService) error
 	// Delete a BackendService given its name.
 	Delete(name string, version meta.Version, scope meta.KeyType) error
 	// Get the health of a BackendService given its name.
diff --git a/pkg/backends/syncer.go b/pkg/backends/syncer.go
index dcfee12318..b3b93600b9 100644
--- a/pkg/backends/syncer.go
+++ b/pkg/backends/syncer.go
@@ -113,7 +113,7 @@ func (s *backendSyncer) ensureBackendService(sp utils.ServicePort) error {
 	}
 
 	if needUpdate {
-		if err := s.backendPool.Update(be); err != nil {
+		if err := s.backendPool.Patch(be); err != nil {
 			return err
 		}
 	}
@@ -305,6 +305,9 @@ func ensureProtocol(be *composite.BackendService, p utils.ServicePort) (needsUpd
 	if be.Protocol == string(p.Protocol) {
 		return false
 	}
+
+	fmt.Printf("protocol needs change; got be = %+v, want protocol = %v\n", be, p.Protocol)
+
 	be.Protocol = string(p.Protocol)
 	return true
 }
diff --git a/pkg/backends/syncer_test.go b/pkg/backends/syncer_test.go
index 88432dbc24..be4f6e11a3 100644
--- a/pkg/backends/syncer_test.go
+++ b/pkg/backends/syncer_test.go
@@ -154,6 +154,9 @@ func newTestSyncer(fakeGCE *gce.Cloud) *backendSyncer {
 	(fakeGCE.Compute().(*cloud.MockGCE)).MockAlphaBackendServices.UpdateHook = mock.UpdateAlphaBackendServiceHook
 	(fakeGCE.Compute().(*cloud.MockGCE)).MockBetaBackendServices.UpdateHook = mock.UpdateBetaBackendServiceHook
 	(fakeGCE.Compute().(*cloud.MockGCE)).MockBackendServices.UpdateHook = mock.UpdateBackendServiceHook
+	(fakeGCE.Compute().(*cloud.MockGCE)).MockAlphaBackendServices.PatchHook = mock.UpdateAlphaBackendServiceHook
+	(fakeGCE.Compute().(*cloud.MockGCE)).MockBetaBackendServices.PatchHook = mock.UpdateBetaBackendServiceHook
+	(fakeGCE.Compute().(*cloud.MockGCE)).MockBackendServices.PatchHook = mock.UpdateBackendServiceHook
 	(fakeGCE.Compute().(*cloud.MockGCE)).MockHealthChecks.UpdateHook = mock.UpdateHealthCheckHook
 	(fakeGCE.Compute().(*cloud.MockGCE)).MockAlphaHealthChecks.UpdateHook = mock.UpdateAlphaHealthCheckHook
 	(fakeGCE.Compute().(*cloud.MockGCE)).MockAlphaRegionHealthChecks.UpdateHook = mock.UpdateAlphaRegionHealthCheckHook