Fix alarm setting typo treshold -> threshold

doc/src/guide/listeners.asciidoc

@@ -332,14 +332,14 @@ processes.
 
 The `alarms` transport option allows you to configure alarms
 which will be triggered when the number of connections tracked
-by one connection supervisor reaches or exceeds the defined treshold.
+by one connection supervisor reaches or exceeds the defined threshold.
 
 The `alarms` transport option takes a map with alarm names as keys and alarm
 options as values.
 
 Any term is allowed as an alarm name.
 
-Alarm options include the alarm type and a treshold that, when reached,
+Alarm options include the alarm type and a threshold that, when reached,
 triggers the given callback. A cooldown prevents the alarm from being
 triggered too often.
 
@@ -350,7 +350,7 @@ triggered too often.
 Alarms = #{
     my_alarm => #{
         type => num_connections,
-        treshold => 100,
+        threshold => 100,
         callback => fun(Ref, Name, ConnSup, ConnPids]) ->
             logger:warning("Warning (~s): "
                     "Supervisor ~s of listener ~s "

doc/src/guide/migrating_from_2.0.asciidoc

@@ -18,7 +18,7 @@ for Erlang/OTP 21 has been removed.
 
 * Alarms can now be configured. The only alarm currently
   available is `num_connections`. When the number of
-  connections goes over a configurable treshold Ranch
+  connections goes over a configurable threshold Ranch
   will call the given callback. This can be used to
   programmatically shut down idle connections to
   make up space for new connections, for example.

doc/src/manual/ranch.asciidoc

@@ -91,7 +91,7 @@ transport_opts(SocketOpts) = #{
     alarms               => #{
                                 term() => #{
                                     type := num_connections,
-                                    treshold := non_neg_integer(),
+                                    threshold := non_neg_integer(),
                                     callback := fun((ref(), term(), pid(), [pid()]) -> any()),
                                     cooldown => non_neg_integer()
                                 }
@@ -118,7 +118,7 @@ None of the options are required.
 alarms (#{})::
 
 Alarms to call a function when the number of connections tracked
-by one connection supervisor reaches or exceeds a defined treshold.
+by one connection supervisor reaches or exceeds a defined threshold.
 +
 The map keys are the alarm names, which can be any `term`. The
 associated values are the respective alarm options, again in a map
@@ -128,9 +128,9 @@ type:::
 
 Must be set to `num_connections`.
 
-treshold:::
+threshold:::
 
-Treshold value, which must be a `non_neg_integer`. When the
+Threshold value, which must be a `non_neg_integer`. When the
 number of connections tracked by a single connection supervisor
 reaches or exceeds this value, The alarm will trigger and call
 the function defined in the `callback` key (see below).

src/ranch.erl

@@ -50,6 +50,9 @@
 -export([require/1]).
 -export([log/4]).
 
+%% Internal
+-export([compat_normalize_alarms_option/1]).
+
 -type max_conns() :: non_neg_integer() | infinity.
 -export_type([max_conns/0]).
 
@@ -59,7 +62,7 @@
 -type alarm(Type, Callback) :: #{
 	type := Type,
 	callback := Callback,
-	treshold := non_neg_integer(),
+	threshold := non_neg_integer(),
 	cooldown => non_neg_integer()
 }.
 
@@ -135,6 +138,7 @@ validate_transport_opt(max_connections, infinity, _) ->
 validate_transport_opt(max_connections, Value, _) ->
 	is_integer(Value) andalso Value >= 0;
 validate_transport_opt(alarms, Alarms, _) ->
+	Alarms1 = compat_normalize_alarms_option(Alarms),
 	maps:fold(
 		fun
 			(_, Opts, true) ->
@@ -143,7 +147,7 @@ validate_transport_opt(alarms, Alarms, _) ->
 				false
 		end,
 		true,
-		Alarms);
+		Alarms1);
 validate_transport_opt(logger, Value, _) ->
 	is_atom(Value);
 validate_transport_opt(num_acceptors, Value, _) ->
@@ -166,9 +170,9 @@ validate_transport_opt(socket_opts, _, _) ->
 validate_transport_opt(_, _, _) ->
 	false.
 
-validate_alarm(Alarm = #{type := num_connections, treshold := Treshold,
+validate_alarm(Alarm = #{type := num_connections, threshold := Threshold,
 		callback := Callback}) ->
-	is_integer(Treshold) andalso Treshold >= 0
+	is_integer(Threshold) andalso Threshold >= 0
 	andalso is_function(Callback, 4)
 	andalso case Alarm of
 		#{cooldown := Cooldown} ->
@@ -632,3 +636,22 @@ log(Level, Format, Args, _) ->
 		debug -> info_msg
 	end,
 	error_logger:Function(Format, Args).
+
+%% For backwards compatibility with the misspelled alarm
+%% setting `treshold`.
+%% See https://github.com/ninenines/ranch/issues/349
+-spec compat_normalize_alarms_option(any()) -> any().
+compat_normalize_alarms_option(Alarms = #{}) ->
+	maps:map(
+		fun
+			(_, Alarm = #{threshold := _}) ->
+				maps:remove(treshold, Alarm);
+			(_, Alarm = #{treshold := Threshold}) ->
+				maps:put(threshold, Threshold, maps:remove(treshold, Alarm));
+			(_, Alarm) ->
+				Alarm
+		end,
+		Alarms
+	);
+compat_normalize_alarms_option(Alarms) ->
+	Alarms.

src/ranch_conns_sup.erl

@@ -287,7 +287,7 @@ trigger_alarms(Ref, Alarms, CurConns) ->
 		Alarms
 	).
 
-trigger_alarm(Ref, AlarmName, {Opts=#{treshold := Treshold, callback := Callback}, undefined}, CurConns) when CurConns >= Treshold ->
+trigger_alarm(Ref, AlarmName, {Opts=#{threshold := Threshold, callback := Callback}, undefined}, CurConns) when CurConns >= Threshold ->
 	ActiveConns = [Pid || {Pid, active} <- get()],
 	case Callback of
 		{Mod, Fun} ->
@@ -306,6 +306,7 @@ schedule_activate_alarm(_, _) ->
 	undefined.
 
 get_alarms(#{alarms := Alarms}) when is_map(Alarms) ->
+	Alarms1 = ranch:compat_normalize_alarms_option(Alarms),
 	maps:fold(
 		fun
 			(Name, Opts = #{type := num_connections, cooldown := _}, Acc) ->
@@ -315,7 +316,7 @@ get_alarms(#{alarms := Alarms}) when is_map(Alarms) ->
 			(_, _, Acc) -> Acc
 		end,
 		#{},
-		Alarms
+		Alarms1
 	);
 get_alarms(_) ->
 	#{}.

test/acceptor_SUITE.erl

@@ -597,7 +597,9 @@ misc_connection_alarms(_) ->
 		Self ! {connection_alarm, {Ref, AlarmName, length(ActiveConns)}}
 	end,
 	Alarms0 = #{
-		test1 => Alarm1 = #{type => num_connections, treshold => 2, cooldown => 0, callback => AlarmCallback},
+		test1 => Alarm1 = #{type => num_connections, threshold => 2, cooldown => 0, callback => AlarmCallback},
+		%% The test2 alarm uses the misspelled treshold key to test for backwards compatibility.
+		%% @TODO: Change to use the proper spelling when treshold gets removed in Ranch 3.0.
 		test2 => Alarm2 = #{type => num_connections, treshold => 3, cooldown => 0, callback => AlarmCallback}
 	},
 	ConnectOpts = [binary, {active, false}, {packet, raw}],