Improve get_cluster_slots/1 API and add a new API to get cluster nodes.

src/eredis_cluster_monitor.erl

@@ -5,9 +5,10 @@
 -export([start_link/0]).
 -export([connect/1]).
 -export([refresh_mapping/1]).
--export([get_state/0, get_state_version/1]).
+-export([get_state/0, get_state_version/1, update_state_init_nodes/1]).
 -export([get_pool_by_slot/1, get_pool_by_slot/2]).
 -export([get_all_pools/0]).
+-export([get_cluster_slots/0, get_cluster_nodes/0]).
 
 %% gen_server.
 -export([init/1]).
@@ -20,10 +21,10 @@
 %% Type definition.
 -include("eredis_cluster.hrl").
 -record(state, {
-    init_nodes :: [#node{}],
-    slots :: tuple(), %% whose elements are integer indexes into slots_maps
-    slots_maps :: tuple(), %% whose elements are #slots_map{}
-    version :: integer()
+    init_nodes = [] :: [#node{}],
+    slots = {} :: tuple(), %% whose elements are integer indexes into slots_maps
+    slots_maps = {} :: tuple(), %% whose elements are #slots_map{}
+    version = 0 :: integer()
 }).
 
 %% API.
@@ -37,6 +38,10 @@ connect(InitServers) ->
 refresh_mapping(Version) ->
     gen_server:call(?MODULE,{reload_slots_map,Version}).
 
+% Used for testing:
+update_state_init_nodes(Nodes) ->
+    gen_server:call(?MODULE,{update_state_init_nodes, Nodes}).
+
 %% =============================================================================
 %% @doc Given a slot return the link (Redis instance) to the mapped
 %% node.
@@ -48,6 +53,12 @@ get_state() ->
     [{cluster_state, State}] = ets:lookup(?MODULE, cluster_state),
     State.
 
+update_state_init_nodes_(Nodes) ->
+    State = get_state(),
+    NewState = State#state{init_nodes = Nodes},
+    true = ets:insert(?MODULE, [{cluster_state, NewState}]),
+    NewState.
+
 get_state_version(State) ->
     State#state.version.
 
@@ -102,26 +113,70 @@ reload_slots_map(State) ->
 
     NewState.
 
+
+-spec get_cluster_slots() -> [[bitstring() | [bitstring()]]].
+get_cluster_slots() ->
+    State = get_state(),
+    get_cluster_slots(State#state.init_nodes).
+
 -spec get_cluster_slots([#node{}]) -> [[bitstring() | [bitstring()]]].
-get_cluster_slots([]) ->
-    throw({error,cannot_connect_to_cluster});
-get_cluster_slots([Node|T]) ->
+get_cluster_slots(InitNodes) ->
+    get_cluster_slots(InitNodes, []).
+
+get_cluster_slots([], ErrorList) ->
+    throw({reply, {error, {cannot_connect_to_cluster, ErrorList}}, #state{}});
+get_cluster_slots([Node|T], ErrorList) ->
     case safe_eredis_start_link(Node#node.address, Node#node.port) of
         {ok,Connection} ->
           case eredis:q(Connection, ["CLUSTER", "SLOTS"]) of
+                {error,<<"ERR unknown command 'CLUSTER'">>} ->
+                    get_cluster_slots_from_single_node(Node);
+                {error,<<"ERR This instance has cluster support disabled">>} ->
+                    get_cluster_slots_from_single_node(Node);
+                {ok, ClusterInfo} ->
+                    case ClusterInfo of
+                        [] when T == [] ->
+                            get_cluster_slots_from_single_node(Node);
+                        _ ->
+                            eredis:stop(Connection),
+                            ClusterInfo
+                    end;
+                Reason ->
+                    eredis:stop(Connection),
+                    get_cluster_slots(T, [{Node, Reason} | ErrorList])
+            end;
+        Reason ->
+            get_cluster_slots(T, [{Node, Reason} | ErrorList])
+    end.
+
+-spec get_cluster_nodes() -> [[bitstring() | [bitstring()]]].
+get_cluster_nodes() ->
+    State = get_state(),
+    get_cluster_nodes(State#state.init_nodes).
+
+-spec get_cluster_nodes([#node{}]) -> [[bitstring() | [bitstring()]]].
+get_cluster_nodes(InitNodes) ->
+    get_cluster_nodes(InitNodes, []).
+
+get_cluster_nodes([], ErrorList) ->
+    throw({reply, {error, {cannot_get_cluster_nodes, ErrorList}}, #state{}});
+get_cluster_nodes([Node|T], ErrorList) ->
+    case safe_eredis_start_link(Node#node.address, Node#node.port) of
+        {ok,Connection} ->
+          case eredis:q(Connection, ["CLUSTER", "NODES"]) of
             {error,<<"ERR unknown command 'CLUSTER'">>} ->
                 get_cluster_slots_from_single_node(Node);
             {error,<<"ERR This instance has cluster support disabled">>} ->
                 get_cluster_slots_from_single_node(Node);
             {ok, ClusterInfo} ->
                 eredis:stop(Connection),
                 ClusterInfo;
-            _ ->
+            Reason ->
                 eredis:stop(Connection),
-                get_cluster_slots(T)
-        end;
-        _ ->
-            get_cluster_slots(T)
+                get_cluster_nodes(T, [{Node, Reason} | ErrorList])
+          end;
+        Reason ->
+            get_cluster_nodes(T, [{Node, Reason} | ErrorList])
   end.
 
 -spec get_cluster_slots_from_single_node(#node{}) ->
@@ -225,6 +280,8 @@ handle_call({reload_slots_map,_}, _From, State) ->
     {reply, ok, State};
 handle_call({connect, InitServers}, _From, _State) ->
     {reply, ok, connect_(InitServers)};
+handle_call({update_state_init_nodes, Nodes}, _From, _State) ->
+    {reply, ok, update_state_init_nodes_(Nodes)};
 handle_call(_Request, _From, State) ->
     {reply, ignored, State}.
 

test/eredis_cluster_tests.erl

@@ -163,6 +163,51 @@ basic_test_() ->
                 eredis_cluster:eval(Script, ScriptHash, ["qrs"], ["evaltest"]),
                 ?assertEqual({ok, <<"evaltest">>}, eredis_cluster:q(["get", "qrs"]))
             end
+            },
+
+            { "get cluster slots and nodes",
+                        fun () ->
+                     NodesInfo = eredis_cluster_monitor:get_cluster_nodes(),
+                     ClusterNodesList = [CNEL || CNEL <- binary:split(NodesInfo,<<"\n">>, [global]), CNEL =/= <<>>],
+                     NodeIdsPL =
+                         lists:flatmap(fun(ClusterNode) ->
+                                               ClusterNodeI = binary:split(ClusterNode,<<" ">>,[global]),
+                                               [Ip, Port] = binary:split(lists:nth(2, ClusterNodeI), <<":">>,[global]),
+                                               Pool = list_to_atom(binary_to_list(Ip) ++ "#" ++ binary_to_list(Port)),
+                                               [{binary_to_list(lists:nth(1, ClusterNodeI)), Pool}]
+                                       end, ClusterNodesList),
+
+                     ?assertMatch([{_, '127.0.0.1#30001'}, {_, '127.0.0.1#30002'},
+                                   {_, '127.0.0.1#30003'}, {_, '127.0.0.1#30004'},
+                                   {_, '127.0.0.1#30005'}, {_, '127.0.0.1#30006'}],
+                                  lists:keysort(2, NodeIdsPL)),
+
+                     % Try to get "cluster slots" and "cluster nodes" for non-existing node:
+                     eredis_cluster_monitor:update_state_init_nodes([{node,"127.0.0.1",30016,
+                                                                      '127.0.0.1#30016'}]),
+
+                     SlotsInfo = 
+                         try eredis_cluster_monitor:get_cluster_slots() of
+                             SI -> SI
+                         catch
+                             throw:SIError -> SIError
+                         end,
+
+                     ?assertMatch({reply, {error, {cannot_connect_to_cluster,
+                                                   [{{node,"127.0.0.1",30016,'127.0.0.1#30016'},
+                                                     {error,no_connection}}]}},_},
+                                  SlotsInfo),
+
+                     NodesInfo2 = try eredis_cluster_monitor:get_cluster_nodes() of
+                                      NI -> NI
+                                  catch
+                                      throw:NIError -> NIError
+                                  end,
+                     ?assertMatch({reply,{error,{cannot_get_cluster_nodes,
+                                                 [{{node,"127.0.0.1",30016,'127.0.0.1#30016'},
+                                                   {error,no_connection}}]}},_},
+                                  NodesInfo2)
+            end
             }
 
       ]