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%% This Source Code Form is subject to the terms of the Mozilla Public
%% License, v. 2.0. If a copy of the MPL was not distributed with this
%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
%%
%% Copyright (c) 2007-2020 VMware, Inc. or its affiliates. All rights reserved.
%%
-module(rabbit_queue_location_random).
-behaviour(rabbit_queue_master_locator).
-include_lib("rabbit_common/include/rabbit.hrl").
-include("amqqueue.hrl").
-export([description/0, queue_master_location/1]).
-rabbit_boot_step({?MODULE,
[{description, "locate queue master random"},
{mfa, {rabbit_registry, register,
[queue_master_locator,
<<"random">>, ?MODULE]}},
{requires, rabbit_registry},
{enables, kernel_ready}]}).
%%---------------------------------------------------------------------------
%% Queue Master Location Callbacks
%%---------------------------------------------------------------------------
description() ->
[{description,
<<"Locate queue master node from cluster in a random manner">>}].
queue_master_location(Q) when ?is_amqqueue(Q) ->
Cluster0 = rabbit_queue_master_location_misc:all_nodes(Q),
Cluster = rabbit_maintenance:filter_out_drained_nodes_local_read(Cluster0),
case Cluster of
[] ->
undefined;
Candidates when is_list(Candidates) ->
RandomPos = erlang:phash2(erlang:monotonic_time(), length(Candidates)),
MasterNode = lists:nth(RandomPos + 1, Candidates),
{ok, MasterNode}
end.
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