discovery/consul: Fix filter parameter not applied to health endpoint

The filter parameter was only being passed to catalog.Services()
but not to health.ServiceMultipleTags(), causing filters on Node
and Node.Meta to be ignored when discovering service instances.

This adds the missing Filter field to QueryOptions in the
consulService.watch() method.

Fixes #16087

Signed-off-by: Mohammad Varmazyar <m.varmazyar@gmail.com>
Signed-off-by: Mohammad Varmazyar <mrvarmazyar@gmail.com>

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## main / unreleased
 
+* [BUGFIX] Discovery/Consul: Fix filter parameter not being applied to health service endpoint, causing Node and Node.Meta filters to be ignored. #16087
+
 ## 3.7.0 / 2025-10-15
 
 * [CHANGE] Remote-write: the following metrics are deprecated:

discovery/consul/consul.go

@@ -499,6 +499,7 @@ func (srv *consulService) watch(ctx context.Context, ch chan<- []*targetgroup.Gr
 		WaitTime:   watchTimeout,
 		AllowStale: srv.discovery.allowStale,
 		NodeMeta:   srv.discovery.watchedNodeMeta,
+		Filter:     srv.discovery.watchedFilter,
 	}
 
 	t0 := time.Now()

discovery/consul/consul_test.go

@@ -240,6 +240,8 @@ func newServer(t *testing.T) (*httptest.Server, *SDConfig) {
 			response = ServiceTestAnswer
 		case "/v1/health/service/test?wait=120000ms":
 			response = ServiceTestAnswer
+		case "/v1/health/service/test?filter=NodeMeta.rack_name+%3D%3D+%222304%22&wait=120000ms":
+			response = ServiceTestAnswer
 		case "/v1/health/service/other?wait=120000ms":
 			response = `[]`
 		case "/v1/catalog/services?node-meta=rack_name%3A2304&stale=&wait=120000ms":
@@ -392,6 +394,54 @@ func TestFilterOption(t *testing.T) {
 	cancel()
 }
 
+// TestFilterOnHealthEndpoint verifies that filter is passed to health service endpoint.
+func TestFilterOnHealthEndpoint(t *testing.T) {
+	filterReceived := false
+	stub := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		response := ""
+		switch r.URL.Path {
+		case "/v1/agent/self":
+			response = AgentAnswer
+		case "/v1/health/service/test":
+			// Verify filter parameter is present in the query
+			filter := r.URL.Query().Get("filter")
+			if filter == `Node.Meta.rack_name == "2304"` {
+				filterReceived = true
+			}
+			response = ServiceTestAnswer
+		default:
+			t.Errorf("Unhandled consul call: %s", r.URL)
+		}
+		w.Header().Add("X-Consul-Index", "1")
+		w.Write([]byte(response))
+	}))
+	defer stub.Close()
+
+	stuburl, err := url.Parse(stub.URL)
+	require.NoError(t, err)
+
+	config := &SDConfig{
+		Server:          stuburl.Host,
+		Services:        []string{"test"},
+		Filter:          `Node.Meta.rack_name == "2304"`,
+		RefreshInterval: model.Duration(1 * time.Second),
+	}
+
+	d := newDiscovery(t, config)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	ch := make(chan []*targetgroup.Group)
+	go func() {
+		d.Run(ctx, ch)
+		close(ch)
+	}()
+	checkOneTarget(t, <-ch)
+	cancel()
+
+	// Verify the filter was actually sent to the health endpoint
+	require.True(t, filterReceived, "Filter parameter should be sent to health service endpoint")
+}
+
 func TestGetDatacenterShouldReturnError(t *testing.T) {
 	for _, tc := range []struct {
 		handler    func(http.ResponseWriter, *http.Request)