fix(pd): populate memberSize in GET / endpoint response (#3003)

* fix(pd): complete GET / stats fix and add test coverage

- Use pdService.getMembers() for memberSize (consistent with cluster())
  instead of RaftEngine directly, as suggested in issue #3002 discussion
- Add dataState field to BriefStatistics: exposes worst partition health
  state across all graphs, the most useful missing operational indicator
- Align graphSize to count only user-facing graphs (endsWith("/g")),
  matching the semantics of cluster() to avoid silent count discrepancy
- Add testQueryIndexInfo() to both RestApiTest classes to assert state,
  leader, memberSize > 0, and storeSize > 0 — catches this class of bug

* fix(pd): relax storeSize assertion in PD-only test environment

---------

Co-authored-by: imbajin <jin@apache.org>

Author: caglareker

hugegraph-pd/hg-pd-service/src/main/java/org/apache/hugegraph/pd/rest/IndexAPI.java

@@ -66,9 +66,35 @@ public BriefStatistics index() throws PDException, ExecutionException, Interrupt
         BriefStatistics statistics = new BriefStatistics();
         statistics.leader = RaftEngine.getInstance().getLeaderGrpcAddress();
         statistics.state = pdService.getStoreNodeService().getClusterStats().getState().toString();
+
+        // Use pdService (consistent with cluster()) rather than RaftEngine directly
+        CallStreamObserverWrap<Pdpb.GetMembersResponse> membersResp =
+                new CallStreamObserverWrap<>();
+        pdService.getMembers(Pdpb.GetMembersRequest.newBuilder().build(), membersResp);
+        statistics.memberSize = membersResp.get().get(0).getMembersList().size();
+
         statistics.storeSize = pdService.getStoreNodeService().getActiveStores().size();
-        statistics.graphSize = pdService.getPartitionService().getGraphs().size();
+        // Filter to user-facing graphs only (consistent with cluster())
+        List<Metapb.Graph> graphs = pdRestService.getGraphs();
+        statistics.graphSize = (int) graphs.stream()
+                                           .filter(g -> g.getGraphName() != null &&
+                                                        g.getGraphName().endsWith("/g"))
+                                           .count();
         statistics.partitionSize = pdService.getStoreNodeService().getShardGroups().size();
+
+        // Derive worst partition health state across all graphs
+        Metapb.PartitionState dataState = Metapb.PartitionState.PState_Normal;
+        for (Metapb.Graph graph : graphs) {
+            if (graph.getState() == Metapb.PartitionState.UNRECOGNIZED) {
+                continue;
+            }
+            if (graph.getState() != null &&
+                graph.getState().getNumber() > dataState.getNumber()) {
+                dataState = graph.getState();
+            }
+        }
+        statistics.dataState = dataState.name();
+
         return statistics;
 
     }
@@ -157,9 +183,13 @@ public RestApiResponse cluster() throws InterruptedException, ExecutionException
     class BriefStatistics {
 
         String state;
+        /** Worst partition health state across all graphs (mirrors cluster().dataState) */
+        String dataState;
         String leader;
         int memberSize;
+        /** Active (online) store count only */
         int storeSize;
+        /** User-facing graphs count (graphName ending with /g) */
         int graphSize;
         int partitionSize;
     }

hugegraph-pd/hg-pd-test/src/main/java/org/apache/hugegraph/pd/rest/RestApiTest.java

@@ -29,6 +29,25 @@
 
 public class RestApiTest extends BaseServerTest {
 
+    @Test
+    public void testQueryIndexInfo() throws URISyntaxException, IOException, InterruptedException,
+                                            JSONException {
+        String url = pdRestAddr + "/";
+        HttpRequest request = HttpRequest.newBuilder()
+                                         .uri(new URI(url))
+                                         .header("Authorization", "Basic c3RvcmU6MTIz")
+                                         .GET()
+                                         .build();
+        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
+        assert response.statusCode() == 200;
+        JSONObject obj = new JSONObject(response.body());
+        assert obj.getString("state") != null;
+        assert obj.getString("leader") != null;
+        assert obj.getInt("memberSize") > 0 : "memberSize should be > 0 for a running cluster";
+        // storeSize can be 0 in PD-only test environments with no store nodes registered
+        assert obj.getInt("storeSize") >= 0;
+    }
+
     @Test
     public void testQueryClusterInfo() throws URISyntaxException, IOException, InterruptedException,
                                               JSONException {

hugegraph-pd/hg-pd-test/src/main/java/org/apache/hugegraph/pd/service/RestApiTest.java

@@ -29,6 +29,24 @@
 
 public class RestApiTest extends BaseServerTest {
 
+    @Test
+    public void testQueryIndexInfo() throws URISyntaxException, IOException, InterruptedException,
+                                            JSONException {
+        String url = pdRestAddr + "/";
+        HttpRequest request = HttpRequest.newBuilder()
+                                         .uri(new URI(url)).header(key, value)
+                                         .GET()
+                                         .build();
+        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
+        assert response.statusCode() == 200;
+        JSONObject obj = new JSONObject(response.body());
+        assert obj.getString("state") != null;
+        assert obj.getString("leader") != null;
+        assert obj.getInt("memberSize") > 0 : "memberSize should be > 0 for a running cluster";
+        // storeSize can be 0 in PD-only test environments with no store nodes registered
+        assert obj.getInt("storeSize") >= 0;
+    }
+
     @Test
     public void testQueryClusterInfo() throws URISyntaxException, IOException, InterruptedException,
                                               JSONException {