chore: Hide replicas from CLUSTER subcmds in managed mode (#4174)

* chore: Hide replicas from `CLUSTER` subcmds in managed mode

Part of #4173 (see for context)

* server.client()

src/server/cluster/cluster_family.cc

@@ -33,6 +33,9 @@ ABSL_FLAG(std::string, cluster_node_id, "",
           "ID within a cluster, used for slot assignment. MUST be unique. If empty, uses master "
           "replication ID (random string)");
 
+ABSL_FLAG(bool, managed_service_info, false,
+          "Hides some implementation details from users when true (i.e. in managed service env)");
+
 ABSL_DECLARE_FLAG(int32_t, port);
 ABSL_DECLARE_FLAG(uint16_t, announce_port);
 
@@ -122,10 +125,12 @@ ClusterShardInfo ClusterFamily::GetEmulatedShardInfo(ConnectionContext* cntx) co
 
     info.master = {.id = id_, .ip = preferred_endpoint, .port = preferred_port};
 
-    for (const auto& replica : server_family_->GetDflyCmd()->GetReplicasRoleInfo()) {
-      info.replicas.push_back({.id = replica.id,
-                               .ip = replica.address,
-                               .port = static_cast<uint16_t>(replica.listening_port)});
+    if (cntx->conn()->IsPrivileged() || !absl::GetFlag(FLAGS_managed_service_info)) {
+      for (const auto& replica : server_family_->GetDflyCmd()->GetReplicasRoleInfo()) {
+        info.replicas.push_back({.id = replica.id,
+                                 .ip = replica.address,
+                                 .port = static_cast<uint16_t>(replica.listening_port)});
+      }
     }
   } else {
     // TODO: We currently don't save the master's ID in the replica

tests/dragonfly/cluster_test.py

@@ -234,7 +234,7 @@ def is_local_host(ip: str) -> bool:
 
     info = answer[2]
     assert len(info) == 3
-    ip_addr = str(info[0], "utf-8")
+    ip_addr = info[0]
     assert is_local_host(ip_addr)
     assert info[1] == port
 
@@ -244,29 +244,29 @@ def is_local_host(ip: str) -> bool:
         replica = replicas[i - 3]
         rep_info = answer[i]
         assert len(rep_info) == 3
-        ip_addr = str(rep_info[0], "utf-8")
+        ip_addr = rep_info[0]
         assert is_local_host(ip_addr)
         assert rep_info[1] == replica.port
         assert rep_info[2] == replica.id
 
     return True
 
 
-@dfly_args({"proactor_threads": 4, "cluster_mode": "emulated"})
+# --managed_service_info means that Dragonfly is running in a managed service, so some details
+# are hidden from users, see https://github.com/dragonflydb/dragonfly/issues/4173
+@dfly_args({"proactor_threads": 4, "cluster_mode": "emulated", "managed_service_info": "true"})
 async def test_emulated_cluster_with_replicas(df_factory):
-    master = df_factory.create(port=BASE_PORT)
+    master = df_factory.create(port=BASE_PORT, admin_port=BASE_PORT + 1000)
     replicas = [df_factory.create(port=BASE_PORT + i, logtostdout=True) for i in range(1, 3)]
 
     df_factory.start_all([master, *replicas])
 
-    c_master = aioredis.Redis(port=master.port)
-    master_id = (await c_master.execute_command("CLUSTER MYID")).decode("utf-8")
+    c_master = master.client()
+    c_master_admin = master.admin_client()
+    master_id = await c_master.execute_command("CLUSTER MYID")
 
-    c_replicas = [aioredis.Redis(port=replica.port) for replica in replicas]
-    replica_ids = [
-        (await c_replica.execute_command("CLUSTER MYID")).decode("utf-8")
-        for c_replica in c_replicas
-    ]
+    c_replicas = [replica.client() for replica in replicas]
+    replica_ids = [(await c_replica.execute_command("CLUSTER MYID")) for c_replica in c_replicas]
 
     for replica, c_replica in zip(replicas, c_replicas):
         res = await c_replica.execute_command("CLUSTER SLOTS")
@@ -279,7 +279,7 @@ async def test_emulated_cluster_with_replicas(df_factory):
     # Connect replicas to master
     for replica, c_replica in zip(replicas, c_replicas):
         rc = await c_replica.execute_command(f"REPLICAOF localhost {master.port}")
-        assert str(rc, "utf-8") == "OK"
+        assert rc == "OK"
 
     await asyncio.sleep(0.5)
 
@@ -290,6 +290,13 @@ async def test_emulated_cluster_with_replicas(df_factory):
         )
 
     res = await c_master.execute_command("CLUSTER SLOTS")
+    assert verify_slots_result(
+        port=master.port,
+        answer=res[0],
+        replicas=[],
+    )
+
+    res = await c_master_admin.execute_command("CLUSTER SLOTS")
     assert verify_slots_result(
         port=master.port,
         answer=res[0],
@@ -308,6 +315,20 @@ async def test_emulated_cluster_with_replicas(df_factory):
             "node_id": master_id,
             "slots": [["0", "16383"]],
         },
+    }
+
+    assert await c_master_admin.execute_command("CLUSTER NODES") == {
+        f"127.0.0.1:{master.port}": {
+            "connected": True,
+            "epoch": "0",
+            "flags": "myself,master",
+            "last_ping_sent": "0",
+            "last_pong_rcvd": "0",
+            "master_id": "-",
+            "migrations": [],
+            "node_id": master_id,
+            "slots": [["0", "16383"]],
+        },
         f"127.0.0.1:{replicas[0].port}": {
             "connected": True,
             "epoch": "0",