PMM-14734 Add ExpectedNodes field

api/ha/v1beta1/ha.proto

@@ -27,6 +27,8 @@ message HANode {
 message ListNodesResponse {
   // List of nodes in the HA cluster.
   repeated HANode nodes = 1;
+  // Expected number of nodes in the cluster
+  int32 expected_nodes = 2;
 }
 
 message StatusRequest {}

api/ha/v1beta1/json/v1beta1.json

@@ -60,6 +60,12 @@
                     }
                   },
                   "x-order": 0
+                },
+                "expected_nodes": {
+                  "type": "integer",
+                  "format": "int32",
+                  "title": "Expected number of nodes in the cluster",
+                  "x-order": 1
                 }
               }
             }

api/swagger/swagger-dev.json

@@ -5209,6 +5209,12 @@
                     }
                   },
                   "x-order": 0
+                },
+                "expected_nodes": {
+                  "type": "integer",
+                  "format": "int32",
+                  "title": "Expected number of nodes in the cluster",
+                  "x-order": 1
                 }
               }
             }

api/swagger/swagger.json

@@ -4236,6 +4236,12 @@
                     }
                   },
                   "x-order": 0
+                },
+                "expected_nodes": {
+                  "type": "integer",
+                  "format": "int32",
+                  "title": "Expected number of nodes in the cluster",
+                  "x-order": 1
                 }
               }
             }

managed/services/ha/ha.go

@@ -51,13 +51,19 @@ func (s *HAServer) ListNodes(_ context.Context, _ *hav1beta1.ListNodesRequest) (
 		return &hav1beta1.ListNodesResponse{Nodes: []*hav1beta1.HANode{}}, nil
 	}
 
+	// Default to 1 for single-node deployment where no peers are configured.
+	expectedNodes := max(len(s.service.params.Nodes), 1)
+
 	s.service.rw.RLock()
 	memberlist := s.service.memberlist
 	raftNode := s.service.raftNode
 	s.service.rw.RUnlock()
 
 	if memberlist == nil {
-		return &hav1beta1.ListNodesResponse{Nodes: []*hav1beta1.HANode{}}, nil
+		return &hav1beta1.ListNodesResponse{
+			Nodes:         []*hav1beta1.HANode{},
+			ExpectedNodes: int32(expectedNodes),
+		}, nil
 	}
 
 	_, leaderID := raftNode.LeaderWithID()
@@ -79,7 +85,10 @@ func (s *HAServer) ListNodes(_ context.Context, _ *hav1beta1.ListNodesRequest) (
 		})
 	}
 
-	return &hav1beta1.ListNodesResponse{Nodes: nodes}, nil
+	return &hav1beta1.ListNodesResponse{
+		Nodes:         nodes,
+		ExpectedNodes: int32(expectedNodes),
+	}, nil
 }
 
 // memberlistStateToString converts memberlist state to a string representation.

managed/services/ha/ha_test.go

@@ -84,6 +84,7 @@ func TestHAServer_ListNodes_HADisabled(t *testing.T) {
 	require.NoError(t, err)
 	require.NotNil(t, resp)
 	assert.Empty(t, resp.Nodes)
+	assert.Equal(t, int32(0), resp.ExpectedNodes)
 }
 
 func TestHAServer_ListNodes_NilMemberlist(t *testing.T) {
@@ -104,6 +105,57 @@ func TestHAServer_ListNodes_NilMemberlist(t *testing.T) {
 	require.NoError(t, err)
 	require.NotNil(t, resp)
 	assert.Empty(t, resp.Nodes)
+	assert.Equal(t, int32(1), resp.ExpectedNodes)
+}
+
+func TestHAServer_ListNodes_ExpectedNodes(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name          string
+		nodes         []string
+		expectedNodes int32
+	}{
+		{
+			name:          "no peers configured defaults to 1",
+			nodes:         nil,
+			expectedNodes: 1,
+		},
+		{
+			name:          "single peer configured",
+			nodes:         []string{"node-1"},
+			expectedNodes: 1,
+		},
+		{
+			name:          "multiple peers configured",
+			nodes:         []string{"node-1", "node-2", "node-3"},
+			expectedNodes: 3,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			service := &Service{
+				params: &models.HAParams{
+					Enabled: true,
+					Nodes:   tt.nodes,
+				},
+				memberlist: nil,
+				rw:         sync.RWMutex{},
+			}
+
+			server := NewHAServer(service)
+
+			resp, err := server.ListNodes(t.Context(), &hav1beta1.ListNodesRequest{})
+
+			require.NoError(t, err)
+			require.NotNil(t, resp)
+			assert.Empty(t, resp.Nodes)
+			assert.Equal(t, tt.expectedNodes, resp.ExpectedNodes)
+		})
+	}
 }
 
 func TestMemberlistStateToString(t *testing.T) {