feat: Use ets for last-known server-time.

Makefile

@@ -24,7 +24,7 @@ doc:
 
 tests:
 	docker run --name ld-test-redis -p 6379:6379 -d redis
-	@$(REBAR3) ct --dir="test,test-redis" --logdir logs/ct --cover
+	@$(REBAR3) ct --dir="test,test-redis" --logdir logs/ct
 	docker rm --force ld-test-redis
 
 #This is used in running releaser. In this environment we do not want to run the redis tests.

src/ldclient_backoff.erl

@@ -7,7 +7,7 @@
 -module(ldclient_backoff).
 
 %% API
--export([init/4, fail/1, succeed/1, fire/1]).
+-export([init/4, init/5, fail/1, succeed/1, fire/1]).
 
 %% Types
 
@@ -19,7 +19,8 @@
     active_since => integer() | undefined,
     destination => pid(),
     value => term(),
-    max_exp => float()
+    max_exp => float(),
+    uniform => fun(() -> float())
 }.
 
 -define(JITTER_RATIO, 0.5).
@@ -36,6 +37,11 @@
 
 -spec init(Initial :: non_neg_integer(), Max :: non_neg_integer(), Destination :: pid(), Value :: term()) -> backoff().
 init(Initial, Max, Destination, Value) ->
+    init(Initial, Max, Destination, Value, fun() -> rand:uniform() end).
+
+%% This version of the function exists for testing and allows injecting the random number source.
+-spec init(Initial :: non_neg_integer(), Max :: non_neg_integer(), Destination :: pid(), Value :: term(), Uniform :: fun(() -> float())) -> backoff().
+init(Initial, Max, Destination, Value, Uniform) ->
     SafeInitial = lists:max([Initial, 1]),
     #{
         initial => SafeInitial, %% Do not allow initial delay to be 0 or negative.
@@ -47,10 +53,12 @@ init(Initial, Max, Destination, Value) ->
         value => Value,
         %% The exponent at which the backoff delay will exceed the maximum.
         %% Beyond this limit the backoff can be set to the max.
-        max_exp => math:ceil(math:log2(Max/SafeInitial))
+        max_exp => math:ceil(math:log2(Max/SafeInitial)),
         %% For reasonable values this should ensure we never overflow.
         %% Note that while integers can be arbitrarily large the math library uses C functions
         %% that are implemented with floats.
+        %% Allow for alternate random number source.
+        uniform => Uniform
     }.
 
 %% @doc Get an updated backoff with updated delay. Does not start a timer automatically.
@@ -98,17 +106,16 @@ update_backoff(#{attempt := Attempt} = Backoff, _ActiveDuration) ->
     Backoff#{current => delay(NewAttempt, Backoff), attempt => NewAttempt, active_since => undefined}.
 
 -spec delay(Attempt :: non_neg_integer(), Backoff :: backoff()) -> non_neg_integer().
-delay(Attempt, #{initial := Initial, max := Max, max_exp := MaxExp} = _Backoff)
+delay(Attempt, #{initial := Initial, max := Max, max_exp := MaxExp, uniform := Uniform} = _Backoff)
   when Attempt - 1 < MaxExp ->
-    jitter(min(backoff(Initial, Attempt), Max));
-delay(_Attempt, #{max := Max} = _Backoff) ->
-    jitter(Max).
+    jitter(min(backoff(Initial, Attempt), Max), Uniform);
+delay(_Attempt, #{max := Max, uniform := Uniform} = _Backoff) ->
+    jitter(Max, Uniform).
 
 -spec backoff(Initial :: non_neg_integer(), Attempt :: non_neg_integer()) -> non_neg_integer().
 backoff(Initial, Attempt) ->
     trunc(Initial * (math:pow(2, Attempt - 1))).
 
--spec jitter(Value :: non_neg_integer()) -> non_neg_integer().
-jitter(Value) ->
-    trunc(Value - (rand:uniform() * ?JITTER_RATIO * Value)).
-
+-spec jitter(Value :: non_neg_integer(), Uniform :: fun(() -> float())) -> non_neg_integer().
+jitter(Value, Uniform) ->
+    trunc(Value - (Uniform() * ?JITTER_RATIO * Value)).

src/ldclient_event_process_server.erl

@@ -27,10 +27,11 @@
     global_private_attributes := ldclient_config:private_attributes(),
     events_uri := string(),
     tag := atom(),
-    dispatcher_state := any(),
-    last_server_time := integer()
+    dispatcher_state := any()
 }.
 
+-define(TABLE_PREFIX, "event_process_state").
+
 %%===================================================================
 %% API
 %%===================================================================
@@ -46,8 +47,17 @@ send_events(Tag, Events, SummaryEvent) ->
 
 -spec get_last_server_time(Tag :: atom()) -> integer().
 get_last_server_time(Tag) ->
-    ServerName = get_local_reg_name(Tag),
-    gen_server:call(ServerName, {get_last_server_time}).
+    TableName = ets_table_name(Tag),
+    case ets:info(TableName) of
+        undefined ->
+            0;
+        _ ->
+            case ets:lookup(TableName, last_known_server_time) of
+                [] -> 0;
+                [{last_known_server_time, LastKnownServerTime}] -> LastKnownServerTime
+            end
+    end.
+
 
 %%===================================================================
 %% Supervision
@@ -67,6 +77,7 @@ start_link(Tag) ->
     {ok, State :: state()} | {ok, State :: state(), timeout() | hibernate} |
     {stop, Reason :: term()} | ignore.
 init([Tag]) ->
+    _Tid = ets:new(ets_table_name(Tag), [set, named_table, {read_concurrency, true}]),
     SdkKey = ldclient_config:get_value(Tag, sdk_key),
     Dispatcher = ldclient_config:get_value(Tag, events_dispatcher),
     GlobalPrivateAttributes = ldclient_config:get_value(Tag, private_attributes),
@@ -77,8 +88,7 @@ init([Tag]) ->
         global_private_attributes => GlobalPrivateAttributes,
         events_uri => EventsUri,
         tag => Tag,
-        dispatcher_state =>  Dispatcher:init(Tag, SdkKey),
-        last_server_time => 0
+        dispatcher_state =>  Dispatcher:init(Tag, SdkKey)
     },
     {ok, State}.
 
@@ -90,8 +100,6 @@ init([Tag]) ->
 -spec handle_call(Request :: term(), From :: from(), State :: state()) ->
     {reply, Reply :: term(), NewState :: state()} |
     {stop, normal, {error, atom(), term()}, state()}.
-handle_call({get_last_server_time}, _From, #{last_server_time := LastServerTime} = State) ->
-    {reply, LastServerTime, State};
 handle_call(_Request, _From, State) ->
     {reply, ok, State}.
 
@@ -101,7 +109,8 @@ handle_cast({send_events, Events, SummaryEvent},
         dispatcher := Dispatcher,
         global_private_attributes := GlobalPrivateAttributes,
         events_uri := Uri,
-        dispatcher_state := DispatcherState
+        dispatcher_state := DispatcherState,
+        tag := Tag
     } = State) ->
     FormattedSummaryEvent = format_summary_event(SummaryEvent),
     FormattedEvents = format_events(Events, GlobalPrivateAttributes),
@@ -111,7 +120,8 @@ handle_cast({send_events, Events, SummaryEvent},
        ok ->
            State;
        {ok, Date} ->
-           State#{last_server_time => Date};
+           ets:insert(ets_table_name(Tag), {last_known_server_time, Date}),
+           State;
        {error, temporary, _Reason} ->
            erlang:send_after(1000, self(), {send, OutputEvents, PayloadId}),
            State;
@@ -321,3 +331,6 @@ send(Dispatcher, DispatcherState, OutputEvents, PayloadId, Uri) ->
 -spec get_local_reg_name(Tag :: atom()) -> atom().
 get_local_reg_name(Tag) ->
     list_to_atom("ldclient_event_process_server_" ++ atom_to_list(Tag)).
+
+-spec ets_table_name(Tag :: atom()) -> atom().
+ets_table_name(Tag) -> list_to_atom(?TABLE_PREFIX ++ atom_to_list(Tag)).

test/ldclient_backoff_SUITE.erl

@@ -60,9 +60,7 @@ end_per_testcase(_, _Config) ->
 %%====================================================================
 
 backoff_client(InitialDelay, Ratio) ->
-    meck:new(rand, [unstick]),
-    meck:expect(rand, uniform, fun() -> Ratio end),
-    ldclient_backoff:init(InitialDelay, 30000, 0, listen).
+    ldclient_backoff:init(InitialDelay, 30000, 0, listen, fun() -> Ratio end).
 
 backoff_client(InitialDelay) ->
     backoff_client(InitialDelay, 0).
@@ -100,7 +98,7 @@ delay_doubles_consecutive_failures(_) ->
     #{current := 16000} = FifthUpdate,
     SixthUpdate = ldclient_backoff:fail(FifthUpdate),
     #{current := 30000} = SixthUpdate.
-    
+
 
 backoff_respects_max(_) ->
     Backoff =
@@ -166,15 +164,15 @@ handles_initial_greater_than_max(_) ->
     30000 = ldclient_backoff:delay(1, Backoff),
     30000 = ldclient_backoff:delay(2, Backoff).
 
-handles_bad_initial_retry(_) -> 
+handles_bad_initial_retry(_) ->
     Backoff = backoff_client(0),
     1 = ldclient_backoff:delay(1, Backoff),
     2 = ldclient_backoff:delay(2, Backoff),
     4 = ldclient_backoff:delay(3, Backoff),
     16384 = ldclient_backoff:delay(15, Backoff),
     30000 = ldclient_backoff:delay(16, Backoff),
     %% Second backoff we do not use backoff_client as meck is already setup.
-    Backoff2 = ldclient_backoff:init(-100, 30000, 0, listen),
+    Backoff2 = backoff_client(-100),
     1 = ldclient_backoff:delay(1, Backoff2),
     2 = ldclient_backoff:delay(2, Backoff2),
     4 = ldclient_backoff:delay(3, Backoff2),