grpcbox_channel can add and remove dynamic endpoints

src/grpcbox_channel.erl

@@ -5,6 +5,8 @@
 -export([start_link/3,
          is_ready/1,
          pick/2,
+         add_endpoints/2,
+         remove_endpoints/3,
          stop/1,
          stop/2]).
 -export([init/1,
@@ -69,6 +71,12 @@ pick(Name, CallType) ->
             {error, undefined_channel}
     end.
 
+add_endpoints(Name, Endpoints) ->
+    gen_statem:call(?CHANNEL(Name), {add_endpoints, Endpoints}).
+
+remove_endpoints(Name, Endpoints, Reason) ->
+    gen_statem:call(?CHANNEL(Name), {remove_endpoints, Endpoints, Reason}).
+
 -spec interceptor(name(), unary | stream) -> grpcbox_client:interceptor() | undefined.
 interceptor(Name, CallType) ->
     case ets:lookup(?CHANNELS_TAB, {Name, CallType}) of
@@ -98,14 +106,13 @@ init([Name, Endpoints, Options]) ->
         pool = Name,
         encoding = Encoding,
         stats_handler = StatsHandler,
-        endpoints = Endpoints
+        endpoints = lists:usort(Endpoints)
     },
-
     case maps:get(sync_start, Options, false) of
         false ->
             {ok, idle, Data, [{next_event, internal, connect}]};
         true ->
-            _ = start_workers(Name, StatsHandler, Encoding, Endpoints),
+            start_workers(Name, StatsHandler, Encoding, Endpoints),
             {ok, connected, Data}
     end.
 
@@ -114,14 +121,33 @@ callback_mode() ->
 
 connected({call, From}, is_ready, _Data) ->
     {keep_state_and_data, [{reply, From, true}]};
+connected({call, From}, {add_endpoints, Endpoints},
+            Data=#data{pool=Pool,
+                        stats_handler=StatsHandler,
+                        encoding=Encoding,
+                        endpoints=TotalEndpoints}) ->
+    NewEndpoints = lists:subtract(Endpoints, TotalEndpoints),
+    NewTotalEndpoints = lists:umerge(TotalEndpoints, Endpoints),
+    start_workers(Pool, StatsHandler, Encoding, NewEndpoints),
+    {keep_state, Data#data{endpoints=NewTotalEndpoints}, [{reply, From, ok}]};
+connected({call, From}, {remove_endpoints, Endpoints, Reason},
+            Data=#data{pool=Pool,
+                        endpoints=TotalEndpoints}) ->
+
+    NewEndpoints = sets:to_list(sets:intersection(sets:from_list(Endpoints),
+                                sets:from_list(TotalEndpoints))),
+    NewTotalEndpoints = lists:subtract(TotalEndpoints, Endpoints),
+    stop_workers(Pool, NewEndpoints, Reason),
+    {keep_state, Data#data{endpoints = NewTotalEndpoints}, [{reply, From, ok}]};
 connected(EventType, EventContent, Data) ->
     handle_event(EventType, EventContent, Data).
 
 idle(internal, connect, Data=#data{pool=Pool,
-                                   stats_handler=StatsHandler,
-                                   encoding=Encoding,
-                                   endpoints=Endpoints}) ->
-    _ = start_workers(Pool, StatsHandler, Encoding, Endpoints),
+                                    stats_handler=StatsHandler,
+                                    encoding=Encoding,
+                                    endpoints=Endpoints}) ->
+
+    start_workers(Pool, StatsHandler, Encoding, Endpoints),
     {next_state, connected, Data};
 idle({call, From}, is_ready, _Data) ->
     {keep_state_and_data, [{reply, From, false}]};
@@ -170,9 +196,16 @@ insert_stream_interceptor(Name, _Type, Interceptors) ->
 
 start_workers(Pool, StatsHandler, Encoding, Endpoints) ->
     [begin
-         gproc_pool:add_worker(Pool, Endpoint),
-         {ok, Pid} = grpcbox_subchannel:start_link(Endpoint, Pool, {Transport, Host, Port, SSLOptions},
-             Encoding, StatsHandler),
-         Pid
-     end || Endpoint={Transport, Host, Port, SSLOptions} <- Endpoints].
+        gproc_pool:add_worker(Pool, Endpoint),
+        {ok, Pid} = grpcbox_subchannel:start_link(Endpoint,
+                                                    Pool, Endpoint, Encoding, StatsHandler),
+        Pid
+     end || Endpoint <- Endpoints].
 
+stop_workers(Pool, Endpoints, Reason) ->
+    [begin
+        case gproc_pool:whereis_worker(Pool, Endpoint) of
+            undefined -> ok;
+            Pid -> grpcbox_subchannel:stop(Pid, Reason)
+        end
+     end || Endpoint <- Endpoints].

test/grpcbox_channel_SUITE.erl

@@ -0,0 +1,40 @@
+-module(grpcbox_channel_SUITE).
+
+-export([all/0,
+        init_per_suite/1,
+        end_per_suite/1,
+        add_and_remove_endpoints/1,
+        pick_worker_strategy/1]).
+
+-include_lib("eunit/include/eunit.hrl").
+
+all() ->
+    [
+        add_and_remove_endpoints
+    ].
+init_per_suite(_Config) ->
+    application:set_env(grpcbox, servers, []),
+    application:ensure_all_started(grpcbox),
+    grpcbox_channel_sup:start_link(),
+    grpcbox_channel_sup:start_child(default_channel, [{https, "127.0.0.1", 8080, #{}}], #{}),
+    grpcbox_channel_sup:start_child(random_channel,
+                                    [{https, "127.0.0.1", 8080, #{}}, {https, "127.0.0.2", 8080, #{}}, {https, "127.0.0.3", 8080, #{}}, {https, "127.0.0.4", 8080, #{}}],
+                                    #{balancer => random}),
+    grpcbox_channel_sup:start_child(hash_channel,
+                                    [{https, "127.0.0.1", 8080, #{}}, {https, "127.0.0.2", 8080, #{}}, {https, "127.0.0.3", 8080, #{}}, {https, "127.0.0.4", 8080, #{}}],
+                                    #{balancer => hash}),
+    grpcbox_channel_sup:start_child(direct_channel,
+                                    [{https, "127.0.0.1", 8080, #{}}, {https, "127.0.0.2", 8080, #{}}, {https, "127.0.0.3", 8080, #{}}, {https, "127.0.0.4", 8080, #{}}],
+                                    #{ balancer => direct}),
+
+    _Config.
+
+end_per_suite(_Config) ->
+    application:stop(grpcbox),
+    ok.
+
+add_and_remove_endpoints(_Config) ->
+    grpcbox_channel:add_endpoints(default_channel, [{https, "127.0.0.2", 8080, #{}}, {https, "127.0.0.3", 8080, #{}}, {https, "127.0.0.4", 8080, #{}}]),
+    ?assertMatch(4, length(gproc_pool:active_workers(default_channel))),
+    grpcbox_channel:remove_endpoints(default_channel, [{https, "127.0.0.1", 8080, #{}}, {https, "127.0.0.2", 8080, #{}}, {https, "127.0.0.4", 8080, #{}}], normal),
+    ?assertMatch(1, length(gproc_pool:active_workers(default_channel))).