fix: Delete HB metric unconditionally for non-HB endpoints

Author: hoffmaen

src/code.cloudfoundry.org/gorouter/registry/registry.go

@@ -484,10 +484,9 @@ func (r *RouteRegistry) reportEndpointsPerPool(uri route.Uri, endpoint *route.En
 		r.reporter.CaptureEndpointsPerPool(pool.NumEndpoints(), string(uri), config.LOAD_BALANCE_HB)
 	} else {
 		// Delete stale entries for routes that have switched from HB to another load balancing algorithm.
-		pool := r.byURI.Find(uri.RouteKey())
-		if pool != nil && pool.LoadBalancingAlgorithm != config.LOAD_BALANCE_HB {
-			r.reporter.DeleteEndpointsPerPool(string(uri), config.LOAD_BALANCE_HB)
-		}
+		// This is called unconditionally because the pool may still report its algorithm as HB
+		// even after the HB setting was removed (setPoolLoadBalancingAlgorithm ignores empty values).
+		r.reporter.DeleteEndpointsPerPool(string(uri), config.LOAD_BALANCE_HB)
 	}
 }
 

src/code.cloudfoundry.org/gorouter/registry/registry_test.go

@@ -698,6 +698,40 @@ var _ = Describe("RouteRegistry", func() {
 			Expect(found).To(BeTrue(), "expected DeleteEndpointsPerPool to be called for the switched route")
 		})
 
+		It("deletes the HB metric when the HB algorithm is removed and endpoint registers with empty algorithm", func() {
+			hbEndpoint := route.NewEndpoint(&route.EndpointOpts{
+				Host:                   "192.168.1.1",
+				Port:                   8080,
+				PrivateInstanceId:      "id-1",
+				LoadBalancingAlgorithm: config.LOAD_BALANCE_HB,
+			})
+
+			r.Register("removed-hb.example.com", hbEndpoint)
+			Expect(reporter.CaptureEndpointsPerPoolCallCount()).To(BeNumerically(">=", 1))
+
+			// Endpoint re-registers with empty LB algorithm (HB setting removed from route)
+			noAlgoEndpoint := route.NewEndpoint(&route.EndpointOpts{
+				Host:                   "192.168.1.1",
+				Port:                   8080,
+				PrivateInstanceId:      "id-1",
+				LoadBalancingAlgorithm: "",
+			})
+
+			deleteBefore := reporter.DeleteEndpointsPerPoolCallCount()
+			r.Register("removed-hb.example.com", noAlgoEndpoint)
+
+			Expect(reporter.DeleteEndpointsPerPoolCallCount()).To(BeNumerically(">", deleteBefore))
+			found := false
+			for i := deleteBefore; i < reporter.DeleteEndpointsPerPoolCallCount(); i++ {
+				uri, algo := reporter.DeleteEndpointsPerPoolArgsForCall(i)
+				if uri == "removed-hb.example.com" && algo == config.LOAD_BALANCE_HB {
+					found = true
+					break
+				}
+			}
+			Expect(found).To(BeTrue(), "expected DeleteEndpointsPerPool to be called when HB algorithm is removed")
+		})
+
 		It("does not change the metric count when an existing HB endpoint is updated", func() {
 			hbEndpoint := route.NewEndpoint(&route.EndpointOpts{
 				Host:                   "192.168.1.1",