Do not try to start ezlib application too frequently

This may overload Erlang applicaton controller

src/ejabberd_listener.erl

@@ -576,6 +576,7 @@ transform_options(Opt, Opts) ->
 validate_module_options(Module, Opts) ->
     try Module:listen_opt_type('') of
 	_ ->
+	    maybe_start_zlib(Opts),
 	    lists:filtermap(
 	      fun({Opt, Val}) ->
 		      case validate_module_option(Module, Opt, Val) of
@@ -664,5 +665,13 @@ all_zero_ip(Opts) ->
 	false -> {0,0,0,0}
     end.
 
+maybe_start_zlib(Opts) ->
+    case proplists:get_bool(zlib, Opts) of
+	true ->
+	    ejabberd:start_app(ezlib);
+	false ->
+	    ok
+    end.
+
 opt_type(listen) -> fun validate_cfg/1;
 opt_type(_) -> [listen].

src/xmpp_socket.erl

@@ -166,7 +166,6 @@ compress(SocketData) -> compress(SocketData, undefined).
 compress(#socket_state{receiver = undefined,
 		       sockmod = SockMod,
 		       socket = Socket} = SocketData, Data) ->
-    ejabberd:start_app(ezlib),
     {ok, ZlibSocket} = ezlib:enable_zlib(SockMod, Socket),
     case Data of
 	undefined -> ok;