add herd_reconnect module

src/herd_reconnect.erl

@@ -0,0 +1,19 @@
+-module(herd_reconnect).
+
+-export([exp_backoff/3, exp_backoff/4]).
+
+
+-spec exp_backoff(integer(), integer(), integer()) -> integer().
+exp_backoff(Attempt, BaseTimeout, MaxTimeout) ->
+    exp_backoff(Attempt, 10, BaseTimeout, MaxTimeout).
+
+
+-spec exp_backoff(integer(), integer(), integer(), integer()) -> integer().
+exp_backoff(Attempt, MaxAttempt, _BaseTimeout, MaxTimeout) when Attempt >= MaxAttempt ->
+    Half = MaxTimeout div 2,
+    Half + random:uniform(Half);
+
+exp_backoff(Attempt, _MaxAttempt, BaseTimeout, MaxTimeout) ->
+    Timeout = min(erlang:round(math:pow(2, Attempt) * BaseTimeout), MaxTimeout),
+    Half = Timeout div 2,
+    Half + random:uniform(Half).