Fix scale test errors caused by upstream server count (#2439)

Problem: When the scale test runs with NGINX Plus with 648 upstream servers, it reports both NGF and NGINX Plus errors, because at some point the upstream zone size is no longer enough to hold all upstream servers. As a result, NGF fails to update NGINX Plus.

Solution: Adjust the upstream server count on the scale test when it runs with NGINX Plus from 648 to 556.

Testing: Scale test passed 5 consecutive times.

tests/suite/scale_test.go

@@ -50,13 +50,16 @@ var _ = Describe("Scale test", Ordered, Label("nfr", "scale"), func() {
 		ngfPodName            string
 		promInstance          framework.PrometheusInstance
 		promPortForwardStopCh = make(chan struct{})
+
+		upstreamServerCount int32
 	)
 
 	const (
-		httpListenerCount   = 64
-		httpsListenerCount  = 64
-		httpRouteCount      = 1000
-		upstreamServerCount = 648
+		httpListenerCount       = 64
+		httpsListenerCount      = 64
+		httpRouteCount          = 1000
+		ossUpstreamServerCount  = 648
+		plusUpstreamServerCount = 556
 	)
 
 	BeforeAll(func() {
@@ -85,6 +88,12 @@ var _ = Describe("Scale test", Ordered, Label("nfr", "scale"), func() {
 		if !clusterInfo.IsGKE {
 			Expect(promInstance.PortForward(k8sConfig, promPortForwardStopCh)).To(Succeed())
 		}
+
+		if *plusEnabled {
+			upstreamServerCount = plusUpstreamServerCount
+		} else {
+			upstreamServerCount = ossUpstreamServerCount
+		}
 	})
 
 	BeforeEach(func() {
@@ -563,7 +572,10 @@ The logs are attached only if there are errors.
 		)
 	})
 
-	It(fmt.Sprintf("scales upstream servers to %d", upstreamServerCount), func() {
+	It(fmt.Sprintf("scales upstream servers to %d for OSS and %d for Plus",
+		ossUpstreamServerCount,
+		plusUpstreamServerCount,
+	), func() {
 		const testName = "TestScale_UpstreamServers"
 
 		testResultsDir := filepath.Join(resultsDir, testName)