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Diffstat (limited to 'lib/sasl/src/overload.erl')
| -rw-r--r-- | lib/sasl/src/overload.erl | 231 |
1 files changed, 0 insertions, 231 deletions
diff --git a/lib/sasl/src/overload.erl b/lib/sasl/src/overload.erl deleted file mode 100644 index 61b925d219..0000000000 --- a/lib/sasl/src/overload.erl +++ /dev/null @@ -1,231 +0,0 @@ -%% -%% %CopyrightBegin% -%% -%% Copyright Ericsson AB 1996-2013. All Rights Reserved. -%% -%% Licensed under the Apache License, Version 2.0 (the "License"); -%% you may not use this file except in compliance with the License. -%% You may obtain a copy of the License at -%% -%% http://www.apache.org/licenses/LICENSE-2.0 -%% -%% Unless required by applicable law or agreed to in writing, software -%% distributed under the License is distributed on an "AS IS" BASIS, -%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -%% See the License for the specific language governing permissions and -%% limitations under the License. -%% -%% %CopyrightEnd% -%% --module(overload). - --export([start_link/0, request/0, set_config_data/2, - get_overload_info/0]). - --export([init/1, handle_call/3, handle_info/2, terminate/2, - format_status/2]). - -%%%----------------------------------------------------------------- -%%% This is a rewrite of overload from BS.3, by Peter Högfeldt. -%%% -%%% DESCRIPTION -%%% -%%% This module implements a server process that keeps record of the -%%% intensity of calls of the request/0 function, and answers accept or -%%% reject depending on if the current average intensity is not greater -%%% than a specified maximum intensity. -%%% -%%% The intensity i is calculated according to the formula: -%%% i(n) = exp(-K*(T(n) - T(n-1)))*i(n-1) + Kappa -%%% where i(n) is the intensity at event n, Kappa is a constant, and -%%% T(n) is the time at event n. -%%% -%%% The constant Kappa can be thought of as 1 / T, where T is the time -%%% constant. Kappa is externally referred to as Weight. -%%% -%%% We keep track of two intensities: the total call intensity and the -%%% intensity of accepted calls. -%%%----------------------------------------------------------------- -%%% TODO -%%% -%%% 3. Hysteresis. -%%% -%%%----------------------------------------------------------------- - --record(state, {total = 0, accept = 0, max, prev_t = get_now(), - kappa, call_counts = {0, 0}, alarm = clear}). - --define(clear_timeout, 30000). - -start_link() -> - gen_server:start_link({local, overload}, overload, [], []). - -init([]) -> - process_flag(priority, high), - MaxIntensity = fetch_config_data(overload_max_intensity), - Kappa = fetch_config_data(overload_weight), - {ok, #state{max = MaxIntensity, kappa = Kappa}}. - -%%----------------------------------------------------------------- -%% Func: request/0 -%% Purpose: This is a request to proceed, e.g. a request to -%% establish a call. -%% Returns: accept | reject -%%----------------------------------------------------------------- -request() -> call(request). - -%%----------------------------------------------------------------- -%% Func: set_config_data/2 -%% Purpose: Set configuration data, and reset intensities. -%% Arguments: MaxIntensity (real > 0), Weight (real > 0). -%% Returns: ok | {error, What} -%% This function is for debugging purposes and is therefore not -%% documented at all. -%%----------------------------------------------------------------- -set_config_data(MaxIntensity, Weight) -> - call({set_config_data, MaxIntensity, Weight}). -%%----------------------------------------------------------------- -%% Func: get_overload_info/0 -%% Returns: A list of tagged items: TotalIntensity, AcceptIntensity, -%% MaxIntensity, Weight, TotalRequests, AcceptedRequests. -%%----------------------------------------------------------------- -get_overload_info() -> call(get_overload_info). - -%%----------------------------------------------------------------- -%% call(Request) -> Term -%%----------------------------------------------------------------- -call(Req) -> - gen_server:call(overload, Req, infinity). - -%%%----------------------------------------------------------------- -%%% Callback functions from gen_server -%%%----------------------------------------------------------------- -handle_call(request, _From, State) -> - #state{total = TI, accept = AI, kappa = Kappa, prev_t = PrevT, - alarm = Alarm} = State, - {TR, AR} = State#state.call_counts, - T = get_now(), - CurI = new_intensity(AI, T, PrevT, Kappa), - NewTI = new_intensity(TI, T, PrevT, Kappa) + Kappa, - if - CurI =< State#state.max -> - %% Hysteresis: If alarm is set, and current intensity has - %% fallen below 75% of max intensity, clear alarm. - NewAlarm = if - CurI =< 0.75*State#state.max -> - clear_alarm(Alarm); - true -> - Alarm - end, - {reply, accept, State#state{call_counts = {TR+1, AR+1}, - prev_t = T, total = NewTI, - accept = CurI + Kappa, - alarm = NewAlarm}, - ?clear_timeout}; - true -> - %% Set alarm if not already set. - NewAlarm = set_alarm(Alarm), - {reply, reject, - State#state{call_counts = {TR+1, AR}, prev_t = T, - total = NewTI, accept = CurI, - alarm = NewAlarm}, - ?clear_timeout} - end; -handle_call({set_config_data, MaxIntensity, Weight}, _From, _State) -> - {reply, ok, #state{max = MaxIntensity, kappa = Weight}, - ?clear_timeout}; -handle_call(get_overload_info, _From, State) -> - #state{max = MI, total = TI, accept = AI, kappa = Kappa, - prev_t = PrevT, call_counts = {TR, AR}} = State, - T = get_now(), - CurI = new_intensity(AI, T, PrevT, Kappa), - NewTI = new_intensity(TI, T, PrevT, Kappa), - Reply = [{total_intensity, NewTI}, {accept_intensity, CurI}, - {max_intensity, MI}, {weight, Kappa}, - {total_requests, TR}, {accepted_requests, AR}], - {reply, Reply, State#state{total = NewTI, accept = CurI}, - ?clear_timeout}. - -handle_info(timeout, State) -> - #state{total = TI, accept = AI, kappa = Kappa, prev_t = PrevT, - alarm = Alarm} = State, - T = get_now(), - CurI = new_intensity(AI, T, PrevT, Kappa), - NewTI = new_intensity(TI, T, PrevT, Kappa), - if - CurI < 0.75* State#state.max -> - NewAlarm = clear_alarm(Alarm), - {noreply, State#state{total = NewTI, accept = CurI, - alarm = NewAlarm}}; - - true -> - {noreply, State#state{total = NewTI, accept = CurI}, - ?clear_timeout} - end; - -handle_info(_, State) -> - {noreply, State, ?clear_timeout}. - -terminate(_Reason, _State) -> - ok. - -%%----------------------------------------------------------------- -%% Internal functions -%%----------------------------------------------------------------- -fetch_config_data(Tag) -> - case application:get_env(sasl, Tag) of - {ok, Value} -> Value; - _ -> fetch_default_data(Tag) - end. - -fetch_default_data(overload_max_intensity) -> 0.8; -fetch_default_data(overload_weight) -> 0.1. - -set_alarm(clear) -> - alarm_handler:set_alarm({overload, []}), - set; -set_alarm(Alarm) -> - Alarm. - -clear_alarm(set) -> - alarm_handler:clear_alarm(overload), - clear; -clear_alarm(Alarm) -> - Alarm. - -%%----------------------------------------------------------------- -%% The catch protects against floating-point exception. -%% -new_intensity(I, T, PrevT, K) -> - Diff = sub(T, PrevT)/1000, - case catch (I*math:exp(-K*Diff)) of - {'EXIT', _} -> % Assume zero. - 0.0; - Res -> - Res - end. - -%% Mask equal to 2^27 - 1, used below. --define(mask27, 16#7ffffff). - -%% Returns number of milliseconds in the range [0, 2^27 - 1]. Must have -%% this since statistics(wall_clock) wraps. Having 2^27 -1 as the max -%% assures that we always get non-negative integers. 2^27 milliseconds -%% are approx. 37.28 hours. -get_now() -> - element(1, statistics(wall_clock)) band ?mask27. - -%% Returns (X - Y) mod 2^27 (which is in the range [0, 2^27 - 1]). -sub(X, Y) -> - (X + (bnot Y) + 1) band ?mask27. - -format_status(Opt, [PDict, #state{max = MI, total = TI, accept = AI, - kappa = K, - call_counts = {TR, AR}}]) -> - [{data, [{"Total Intensity", TI}, - {"Accept Intensity", AI}, - {"Max Intensity", MI}, - {"Weight", K}, - {"Total requests", TR}, - {"Accepted requests", AR}]} | - misc_supp:format_pdict(Opt, PDict, [])]. |