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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 Developer of the Original Code is GoPivotal, Inc.
%% Copyright (c) 2010-2014 GoPivotal, Inc. All rights reserved.
%%
-module(rabbit_prequeue).
%% This is the initial gen_server that all queue processes start off
%% as. It handles the decision as to whether we need to start a new
%% slave, a new master/unmirrored, whether we lost a race to declare a
%% new queue, or whether we are in recovery. Thus a crashing queue
%% process can restart from here and always do the right thing.
-export([start_link/1]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
code_change/3]).
-behaviour(gen_server2).
-include("rabbit.hrl").
start_link(Q) ->
gen_server2:start_link(?MODULE, Q, []).
%%----------------------------------------------------------------------------
init(Q) ->
%% Hand back to supervisor ASAP
gen_server2:cast(self(), init),
{ok, Q#amqqueue{pid = self()}, hibernate,
{backoff, ?HIBERNATE_AFTER_MIN, ?HIBERNATE_AFTER_MIN,
?DESIRED_HIBERNATE}}.
handle_call(Msg, _From, State) ->
{stop, {unexpected_call, Msg}, {unexpected_call, Msg}, State}.
handle_cast(init, Q) ->
case whereis(rabbit_recovery) of
undefined -> init_non_recovery(Q);
_Pid -> init_recovery(Q)
end;
handle_cast(Msg, State) ->
{stop, {unexpected_cast, Msg}, State}.
handle_info(Msg, State) ->
{stop, {unexpected_info, Msg}, State}.
terminate(_Reason, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
%%----------------------------------------------------------------------------
init_non_recovery(Q = #amqqueue{name = QueueName}) ->
Result = rabbit_misc:execute_mnesia_transaction(
fun () ->
case mnesia:wread({rabbit_queue, QueueName}) of
[] ->
{decl, rabbit_amqqueue:internal_declare(Q)};
[ExistingQ = #amqqueue{pid = QPid}] ->
case rabbit_misc:is_process_alive(QPid) of
true -> {decl, {existing, ExistingQ}};
false -> exit(todo)
end
end
end),
case Result of
{decl, DeclResult} ->
%% We have just been declared. Block waiting for an init
%% call so that we don't respond to any other message first
receive {'$gen_call', From, {init, new}} ->
case DeclResult of
{new, Fun} ->
Q1 = Fun(),
rabbit_amqqueue_process:init_declared(new,From, Q1);
{F, _} when F =:= absent; F =:= existing ->
gen_server2:reply(From, DeclResult),
{stop, normal, Q}
end
end
end.
init_recovery(Q) ->
rabbit_misc:execute_mnesia_transaction(
fun () -> ok = rabbit_amqqueue:store_queue(Q) end),
%% Again block waiting for an init call.
receive {'$gen_call', From, {init, Terms}} ->
rabbit_amqqueue_process:init_declared(Terms, From, Q)
end.
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