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%% The contents of this file are subject to the Mozilla Public License
%% Version 1.1 (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.mozilla.org/MPL/
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
%% License for the specific language governing rights and limitations
%% under the License.
%%
%% The Original Code is RabbitMQ.
%%
%% The Initial Developers of the Original Code are LShift Ltd,
%% Cohesive Financial Technologies LLC, and Rabbit Technologies Ltd.
%%
%% Portions created before 22-Nov-2008 00:00:00 GMT by LShift Ltd,
%% Cohesive Financial Technologies LLC, or Rabbit Technologies Ltd
%% are Copyright (C) 2007-2008 LShift Ltd, Cohesive Financial
%% Technologies LLC, and Rabbit Technologies Ltd.
%%
%% Portions created by LShift Ltd are Copyright (C) 2007-2010 LShift
%% Ltd. Portions created by Cohesive Financial Technologies LLC are
%% Copyright (C) 2007-2010 Cohesive Financial Technologies
%% LLC. Portions created by Rabbit Technologies Ltd are Copyright
%% (C) 2007-2010 Rabbit Technologies Ltd.
%%
%% All Rights Reserved.
%%
%% Contributor(s): ______________________________________.
%%
-module(rabbit_load).
-export([local_load/0, remote_loads/0, pick/0]).
-define(FUDGE_FACTOR, 0.98).
-define(TIMEOUT, 100).
%%----------------------------------------------------------------------------
-ifdef(use_specs).
-type(load() :: {{non_neg_integer(), integer() | 'unknown'}, node()}).
-spec(local_load/0 :: () -> load()).
-spec(remote_loads/0 :: () -> [load()]).
-spec(pick/0 :: () -> node()).
-endif.
%%----------------------------------------------------------------------------
local_load() ->
LoadAvg = case whereis(cpu_sup) of
undefined -> unknown;
_ -> case cpu_sup:avg1() of
L when is_integer(L) -> L;
{error, timeout} -> unknown
end
end,
{{statistics(run_queue), LoadAvg}, node()}.
remote_loads() ->
{ResL, _BadNodes} =
rpc:multicall(nodes(), ?MODULE, local_load, [], ?TIMEOUT),
ResL.
pick() ->
RemoteLoads = remote_loads(),
{{RunQ, LoadAvg}, Node} = local_load(),
%% add bias towards current node; we rely on Erlang's term order
%% of SomeFloat < local_unknown < unknown.
AdjustedLoadAvg = case LoadAvg of
unknown -> local_unknown;
_ -> LoadAvg * ?FUDGE_FACTOR
end,
Loads = [{{RunQ, AdjustedLoadAvg}, Node} | RemoteLoads],
{_, SelectedNode} = lists:min(Loads),
SelectedNode.
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