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fix: prevent deleting backends still referenced by a frontend #255

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Merged
Tomy2e merged 1 commit into from
Jul 20, 2026
Merged

fix: prevent deleting backends still referenced by a frontend #255

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46 changes: 33 additions & 13 deletions scaleway/loadbalancers.go
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -662,17 +662,6 @@ func (l *loadbalancers) updateLoadBalancer(ctx context.Context, loadbalancer *sc
}
}

// Remove extra backends
for _, b := range backendsOps.remove {
klog.V(3).Infof("deleting backend: %s port: %d loadbalancer: %s", b.ID, b.ForwardPort, loadbalancer.ID)
if err := l.api.DeleteBackend(&scwlb.ZonedAPIDeleteBackendRequest{
Zone: loadbalancer.Zone,
BackendID: b.ID,
}); err != nil {
return fmt.Errorf("failed deleting backend: %s port: %d loadbalancer: %s err: %v", b.ID, b.ForwardPort, loadbalancer.ID, err)
}
}

for _, port := range service.Spec.Ports {
var backend *scwlb.Backend
// Update backend
Expand Down Expand Up @@ -779,6 +768,18 @@ func (l *loadbalancers) updateLoadBalancer(ctx context.Context, loadbalancer *sc
}
}

// Remove extra backends. This must happen after frontends have been rewired above,
// since a backend cannot be deleted while still referenced by a frontend.
for _, b := range backendsOps.remove {
klog.V(3).Infof("deleting backend: %s port: %d loadbalancer: %s", b.ID, b.ForwardPort, loadbalancer.ID)
if err := l.api.DeleteBackend(&scwlb.ZonedAPIDeleteBackendRequest{
Zone: loadbalancer.Zone,
BackendID: b.ID,
}); err != nil {
return fmt.Errorf("failed deleting backend: %s port: %d loadbalancer: %s err: %v", b.ID, b.ForwardPort, loadbalancer.ID, err)
}
}

if !lbExternallyManaged {
loadBalancerType := getLoadBalancerType(service)
if loadBalancerType != "" && strings.ToLower(loadbalancer.Type) != loadBalancerType {
Expand Down Expand Up @@ -1183,8 +1184,11 @@ func servicePortToFrontend(service *v1.Service, loadbalancer *scwlb.LB, port v1.
}

return &scwlb.Frontend{
Name: fmt.Sprintf("%s_%s_%d", string(service.UID), strings.ToLower(string(port.Protocol)), port.Port),
InboundPort: port.Port,
Name: fmt.Sprintf("%s_%s_%d", string(service.UID), strings.ToLower(string(port.Protocol)), port.Port),
InboundPort: port.Port,
// Backend is a stub carrying only the desired ForwardPort, used by frontendEquals
// to detect a frontend still wired to a stale backend (e.g. after a NodePort change).
Backend: &scwlb.Backend{ForwardPort: port.NodePort},
TimeoutClient: &timeoutClient,
ConnectionRateLimit: connectionRateLimit,
CertificateIDs: certificateIDs,
Expand Down Expand Up @@ -1443,6 +1447,10 @@ func frontendEquals(got, want *scwlb.Frontend) bool {
klog.V(3).Infof("frontend.InboundPort: %d - %d", got.InboundPort, want.InboundPort)
return false
}
if !backendForwardPortEqual(got.Backend, want.Backend) {
klog.V(3).Infof("frontend.Backend.ForwardPort: %v - %v", got.Backend, want.Backend)
return false
}
if !durationPtrEqual(got.TimeoutClient, want.TimeoutClient) {
klog.V(3).Infof("frontend.TimeoutClient: %s - %s", got.TimeoutClient, want.TimeoutClient)
return false
Expand Down Expand Up @@ -1898,6 +1906,18 @@ func uint32PtrEqual(got, want *uint32) bool {
return *got == *want
}

// backendForwardPortEqual returns true if both backends are nil, or if both are
// non-nil and reference the same ForwardPort
func backendForwardPortEqual(got, want *scwlb.Backend) bool {
if got == nil && want == nil {
return true
}
if got == nil || want == nil {
return false
}
return got.ForwardPort == want.ForwardPort
}

// chunkArray takes an array and split it in chunks of a given size
func chunkArray(array []string, maxChunkSize int) [][]string {
result := [][]string{}
Expand Down
32 changes: 32 additions & 0 deletions scaleway/loadbalancers_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -399,6 +399,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{},
},
Expand All @@ -417,6 +418,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &otherTimeout,
CertificateIDs: []string{},
},
Expand All @@ -435,6 +437,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{"uid-1"},
},
Expand All @@ -453,6 +456,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{"uid-1"},
},
Expand All @@ -471,6 +475,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{"uid-1"},
},
Expand All @@ -489,6 +494,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{"uid-1", "uid-2"},
},
Expand All @@ -507,6 +513,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{"uid-1", "uid-2"},
},
Expand All @@ -525,6 +532,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{},
ConnectionRateLimit: func() *uint32 { v := uint32(100); return &v }(),
Expand All @@ -544,6 +552,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{},
EnableAccessLogs: true,
Expand All @@ -563,6 +572,7 @@ func TestServicePortToFrontend(t *testing.T) {
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 0},
TimeoutClient: &defaultTimeout,
CertificateIDs: []string{},
EnableHTTP3: true,
Expand Down Expand Up @@ -758,6 +768,28 @@ func TestFrontendEquals(t *testing.T) {
},
false,
},
{
// A frontend still wired to a backend with a stale ForwardPort (e.g. after
// the service's NodePort changed) must not be considered equal, otherwise it
// never gets rewired before the stale backend is deleted.
"with a different backend forward port",
&scwlb.Frontend{
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 30001},
TimeoutClient: &otherTimeout,
CertificateIDs: []string{"uid-1", "uid-2"},
},
&scwlb.Frontend{
ID: "uid-1",
Name: "uid_tcp_1234",
InboundPort: 1234,
Backend: &scwlb.Backend{ForwardPort: 30002},
TimeoutClient: &otherTimeout,
CertificateIDs: []string{"uid-2", "uid-1"},
},
false,
},
{
"with a different timeout",
&scwlb.Frontend{
Expand Down