Make it possible to tune socket buffer sizes

src/mtp_handler.erl

@@ -63,11 +63,14 @@ ranch_init({Ref, Socket, Transport, _} = Opts) ->
     case init(Opts) of
         {ok, State} ->
             ok = ranch:accept_ack(Ref),
-            ok = Transport:setopts(Socket,
+            BufSize = application:get_env(?APP, upstream_socket_buffer_size,
+                                          ?MAX_SOCK_BUF_SIZE),
+            ok = Transport:setopts(
+                   Socket,
                    [{active, once},
                     %% {recbuf, ?MAX_SOCK_BUF_SIZE},
                     %% {sndbuf, ?MAX_SOCK_BUF_SIZE},
-                                    {buffer, ?MAX_SOCK_BUF_SIZE}
+                    {buffer, BufSize}
                    ]),
             gen_server:enter_loop(?MODULE, [], State);
         error ->
@@ -361,10 +364,13 @@ handle_upstream_header(DcId, S) ->
 -define(SEND_TIMEOUT, 60 * 1000).
 
 connect(Host, Port) ->
+    BufSize = application:get_env(?APP, downstream_socket_buffer_size,
+                                  ?MAX_SOCK_BUF_SIZE),
     SockOpts = [{active, once},
                 {packet, raw},
-                binary,
+                {mode, binary},
                 {send_timeout, ?SEND_TIMEOUT},
+                {buffer, BufSize},
                 %% {nodelay, true},
                 {keepalive, true}],
     case mtp_metric:rt([?APP, downstream_connect_duration, seconds],
@@ -372,9 +378,6 @@ connect(Host, Port) ->
                            gen_tcp:connect(Host, Port, SockOpts, ?CONN_TIMEOUT)
                    end) of
         {ok, Sock} ->
-            ok = inet:setopts(Sock, [%% {recbuf, ?MAX_SOCK_BUF_SIZE},
-                                     %% {sndbuf, ?MAX_SOCK_BUF_SIZE},
-                                     {buffer, ?MAX_SOCK_BUF_SIZE}]),
             {ok, Sock};
         {error, _} = Err ->
             Err

src/mtproto_proxy.app.src

@@ -60,6 +60,11 @@
         %% module with function `notify/4' exported.
         %% See mtp_metric:notify/4 for details
         %% {metric_backend, my_metric_backend}
+
+        %% User-space recv socket buffer sizes. Set to higher if you have
+        %% enough RAM
+        %% {upstream_socket_buffer_size, 51200},   %50kb
+        %% {downstream_socket_buffer_size, 51200}   %50kb
        ]},
   {modules, []},