Remove zone size for invalid backend ref (#1931)

Problem: The invalid-backend-ref size of 32k is too small for some environments causing an inability of the gateway to program.

Solution: Do not specify zone size for invalid-backend-ref so that NGINX does not share upstream state across backends. This is ok for this specific upstream because we will only ever proxy to one backend.

Testing: Adjusted unit test to match. Deployed NGF with HTTPRoutes and verified it correctly still generates zone sizes for normal upstreams, an upstream missing its endpoint (service is present but no deployment/pod), and invalid-backend-ref

internal/mode/static/nginx/config/upstreams.go

@@ -21,8 +21,6 @@ const (
 	ossZoneSize = "512k"
 	// plusZoneSize is the upstream zone size for nginx plus.
 	plusZoneSize = "1m"
-	// invalidBackendZoneSize is the upstream zone size for the invalid backend upstream.
-	invalidBackendZoneSize = "32k"
 )
 
 func (g GeneratorImpl) executeUpstreams(conf dataplane.Configuration) []executeResult {
@@ -81,9 +79,9 @@ func (g GeneratorImpl) createUpstream(up dataplane.Upstream) http.Upstream {
 }
 
 func createInvalidBackendRefUpstream() http.Upstream {
+	// ZoneSize is omitted since we will only ever proxy to one destination/backend.
 	return http.Upstream{
-		Name:     invalidBackendRef,
-		ZoneSize: invalidBackendZoneSize,
+		Name: invalidBackendRef,
 		Servers: []http.UpstreamServer{
 			{
 				Address: nginx500Server,

internal/mode/static/nginx/config/upstreams_template.go

@@ -8,7 +8,9 @@ const upstreamsTemplateText = `
 {{ range $u := . }}
 upstream {{ $u.Name }} {
     random two least_conn;
+    {{ if $u.ZoneSize -}}
     zone {{ $u.Name }} {{ $u.ZoneSize }};
+    {{ end -}}
     {{ range $server := $u.Servers }}
     server {{ $server.Address }};
     {{- end }}

internal/mode/static/nginx/config/upstreams_test.go

@@ -128,8 +128,7 @@ func TestCreateUpstreams(t *testing.T) {
 			},
 		},
 		{
-			Name:     invalidBackendRef,
-			ZoneSize: invalidBackendZoneSize,
+			Name: invalidBackendRef,
 			Servers: []http.UpstreamServer{
 				{
 					Address: nginx500Server,