add grpcbox_channel stop/2 alternative

Adds stop/2 for providing more graceful termination of a channel.
stop/1 will kill h2 streams which causes crash reports. For a similar
termination without crash reports grpcbox_channel:stop(Name, shutdown)
can now be called. Calling grpcbox_channel:stop(Name, normal) will
shutdown the h2_connection with stop instead of calling exit for it.

src/grpcbox_channel.erl

@@ -5,7 +5,8 @@
 -export([start_link/3,
          is_ready/1,
          pick/2,
-         stop/1]).
+         stop/1,
+         stop/2]).
 -export([init/1,
          callback_mode/0,
          terminate/3,
@@ -78,7 +79,9 @@ interceptor(Name, CallType) ->
     end.
 
 stop(Name) ->
-    gen_statem:stop(?CHANNEL(Name)).
+    stop(Name, {shutdown, force_delete}).
+stop(Name, Reason) ->
+    gen_statem:stop(?CHANNEL(Name), Reason, infinity).
 
 init([Name, Endpoints, Options]) ->
     process_flag(trap_exit, true),
@@ -128,8 +131,11 @@ idle(EventType, EventContent, Data) ->
 handle_event(_, _, Data) ->
     {keep_state, Data}.
 
-terminate(_Reason, _State, #data{pool=Name}) ->
-    gproc_pool:force_delete(Name),
+terminate({shutdown, force_delete}, _State, #data{pool=Name}) ->
+    gproc_pool:force_delete(Name);
+terminate(Reason, _State, #data{pool=Name}) ->
+    [grpcbox_subchannel:stop(Pid, Reason) || {_Channel, Pid} <- gproc_pool:active_workers(Name)],
+    gproc_pool:delete(Name),
     ok.
 
 insert_interceptors(Name, Interceptors) ->

src/grpcbox_subchannel.erl

@@ -4,7 +4,8 @@
 
 -export([start_link/5,
          conn/1,
-         conn/2]).
+         conn/2,
+         stop/2]).
 -export([init/1,
          callback_mode/0,
          terminate/3,
@@ -35,6 +36,9 @@ conn(Pid, Timeout) ->
         exit:{timeout, _} -> {error, timeout}
     end.
 
+stop(Pid, Reason) ->
+    gen_statem:stop(Pid, Reason, infinity).
+
 init([Name, Channel, Endpoint, Encoding, StatsHandler]) ->
     process_flag(trap_exit, true),
     gproc_pool:connect_worker(Channel, Name),
@@ -90,12 +94,19 @@ terminate(_Reason, _State, #data{conn=undefined,
     gproc_pool:disconnect_worker(Channel, Endpoint),
     gproc_pool:remove_worker(Channel, Endpoint),
     ok;
-terminate(_Reason, _State, #data{conn=Pid,
+terminate(normal, _State, #data{conn=Pid,
                                  endpoint=Endpoint,
                                  channel=Channel}) ->
     h2_connection:stop(Pid),
     gproc_pool:disconnect_worker(Channel, Endpoint),
     gproc_pool:remove_worker(Channel, Endpoint),
+    ok;
+terminate(Reason, _State, #data{conn=Pid,
+                                 endpoint=Endpoint,
+                                 channel=Channel}) ->
+    exit(Pid, Reason),
+    gproc_pool:disconnect_worker(Channel, Endpoint),
+    gproc_pool:remove_worker(Channel, Endpoint),
     ok.
 
 connect(Data=#data{conn=undefined,