OCPBUGS-42045: Add an Internal Warmup for IBMCloud DNS in E2E

During testing, we found that IBMCloud's DNS resolution works well from
outside the cluster (e.g., the test runner cluster). However, internal
DNS queries within the test cluster trigger to an unchangeable
~30-minute negative caching TTL.

This E2E test fix introduces an internal warmup period for IBMCloud
clusters to mitigate the negative caching issue. Only one test,
TestUnmanagedDNSToManagedDNSInternalIngressController, requires this
workaround.

test/e2e/operator_test.go

@@ -125,6 +125,14 @@ var (
 	operandNamespace  = operatorcontroller.DefaultOperandNamespace
 	defaultName       = types.NamespacedName{Namespace: operatorNamespace, Name: manifests.DefaultIngressControllerName}
 	clusterConfigName = types.NamespacedName{Namespace: operatorNamespace, Name: manifests.ClusterIngressConfigName}
+
+	// Platforms that need a DNS "warmup" period for internal (inside the test cluster) DNS resolution.
+	// The warmup period is a period of delay before the first query is executed to avoid negative caching.
+	// This is not intended for external (i.e. the test runner cluster) DNS resolution.
+	platformsNeedInternalDNSWarmup = map[configv1.PlatformType]time.Duration{
+		// 7 minutes of warmup was required past testing for internal IBMCloud DNS queries.
+		configv1.IBMCloudPlatformType: 7 * time.Minute,
+	}
 )
 
 const (

test/e2e/util_test.go

@@ -766,6 +766,10 @@ func verifyInternalIngressController(t *testing.T, name types.NamespacedName, ho
 		}
 	}()
 
+	// Since we've created a new IngressController, and we are about to use a curl pod to query the
+	// wildcard DNS record, we need to wait for platforms that require a warmup period for internal queries.
+	waitForInternalDNSWarmup(t)
+
 	extraArgs := []string{
 		"--header", "HOST:" + echoRoute.Spec.Host,
 		"-v",
@@ -849,6 +853,16 @@ func verifyInternalIngressController(t *testing.T, name types.NamespacedName, ho
 	}
 }
 
+// waitForInternalDNSWarmup waits for a designated "warmup" period
+// to prevent negative caching on platforms that require it.
+func waitForInternalDNSWarmup(t *testing.T) {
+	warmup, _ := platformsNeedInternalDNSWarmup[infraConfig.Status.PlatformStatus.Type]
+	if warmup > 0 {
+		t.Logf("this platform requires DNS warmup time to avoid negative caching...waiting for %s", warmup)
+		time.Sleep(warmup)
+	}
+}
+
 // assertDeleted tries to delete a cluster resource, and causes test failure if the delete fails.
 func assertDeleted(t *testing.T, cl client.Client, thing client.Object) {
 	t.Helper()