Tau - move keepalive out of the tau_server supervision tree

It's now more top level (is it ok doing this?) so it doesn't get restarted - this process should only be started once and left alone.

Author: samaaron

app/server/beam/tau/lib/tau.ex

@@ -26,6 +26,7 @@ use Application
 
     # Although we don't use the supervisor name below directly,
     # it can be useful when debugging or introspecting the system.
+    :tau_keepalive.start_link(daemon_port)
     :tau_server_sup.start_link()
   end
 

app/server/beam/tau/src/tau_server/tau_keepalive.erl

@@ -14,24 +14,24 @@
 
 -module(tau_keepalive).
 
--export([start/1, init/1, loop/1]).
+-export([start_link/1, init/1, loop/1]).
 
-start(DaemonPortNum) ->
-    spawn(?MODULE, init, [DaemonPortNum]).
+start_link(DaemonPortNum) ->
+    spawn_link(?MODULE, init, [DaemonPortNum]).
 
 init(DaemonPortNum) ->
     logger:info("connecting to Daemon via TCP...", []),
     {ok, DaemonSocket} = gen_tcp:connect({127,0,0,1}, DaemonPortNum, [
                                                                       binary,
                                                                       {active, true},
                                                                       {packet, 4},
-                                                                      {keepalive, true}
+                                                                      {keepalive, false}
                                                                      ]),
     OSPid = os:getpid(),
     PidMsg = osc:encode(["/tau_pid", OSPid]),
     logger:info("Sending Pid ~p to Daemon...", [OSPid]),
     gen_tcp:send(DaemonSocket, PidMsg),
-    KillSwitch = erlang:start_timer(5000, self(), trigger_kill_switch),
+    KillSwitch = erlang:send_after(5000, self(), trigger_kill_switch),
     logger:info("Waiting for keepalive messages..."),
     loop(KillSwitch).
 
@@ -41,8 +41,8 @@ loop(KillSwitch) ->
             try osc:decode(Bin) of
                 {cmd, ["/system/keepalive"]} ->
                     logger:debug("Received keepalive message from Daemon", []),
-                    erlang:cancel_timer(KillSwitch),
-                    NewKillSwitch = erlang:start_timer(5000, self(), trigger_kill_switch),
+                    ok = erlang:cancel_timer(KillSwitch, [{async, true}, {info, false}]),
+                    NewKillSwitch = erlang:send_after(5000, self(), trigger_kill_switch),
                     ?MODULE:loop(NewKillSwitch);
                 Other ->
                     logger:error("Unexpected message from Daemon:~p", [Other]),
@@ -53,7 +53,7 @@ loop(KillSwitch) ->
                         [Bin, Class, Term, Trace]),
                     ?MODULE:loop(KillSwitch)
             end;
-        {timeout, _Timer, trigger_kill_switch} ->
+        trigger_kill_switch ->
             logger:info("Tau kill switch activated. Shutting down....", []),
             init:stop();
         Any ->

app/server/beam/tau/src/tau_server/tau_server_api.erl

@@ -74,8 +74,6 @@ start_link(CueServer, MIDIServer, LinkServer) ->
 init(Parent, CueServer, MIDIServer, LinkServer) ->
     register(?SERVER, self()),
     APIPort = application:get_env(?APPLICATION, api_port, undefined),
-    DaemonPort = application:get_env(?APPLICATION, daemon_port, undefined),
-
     logger:info("~n"
               "+--------------------------------------+~n"
               "    This is the Sonic Pi API Server     ~n"
@@ -87,7 +85,6 @@ init(Parent, CueServer, MIDIServer, LinkServer) ->
 
     {ok, APISocket} = gen_udp:open(APIPort, [binary, {ip, loopback}]),
 
-    _KeepAlivePid = tau_keepalive:start(DaemonPort),
 
     %% tell parent we have allocated resources and are up and running
     proc_lib:init_ack(Parent, {ok, self()}),