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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_sharding_interceptor).
-include_lib("rabbit_common/include/rabbit_framing.hrl").
-behaviour(rabbit_channel_interceptor).
-export([description/0, intercept/3, applies_to/0, init/1]).
%% exported for tests
-export([consumer_count/1]).
-import(rabbit_sharding_util, [a2b/1, shards_per_node/1]).
-import(rabbit_misc, [r/3, format/2, protocol_error/3]).
-rabbit_boot_step({?MODULE,
[{description, "sharding interceptor"},
{mfa, {rabbit_registry, register,
[channel_interceptor,
<<"sharding interceptor">>, ?MODULE]}},
{cleanup, {rabbit_registry, unregister,
[channel_interceptor,
<<"sharding interceptor">>]}},
{requires, rabbit_registry},
{enables, recovery}]}).
init(Ch) ->
rabbit_channel:get_vhost(Ch).
description() ->
[{description, <<"Sharding interceptor for channel methods">>}].
intercept(#'basic.consume'{queue = QName} = Method, Content, VHost) ->
case queue_name(VHost, QName) of
{ok, QName2} ->
{Method#'basic.consume'{queue = QName2}, Content};
{error, QName} ->
precondition_failed("Error finding sharded queue for: ~p", [QName])
end;
intercept(#'basic.get'{queue = QName} = Method, Content, VHost) ->
case queue_name(VHost, QName) of
{ok, QName2} ->
{Method#'basic.get'{queue = QName2}, Content};
{error, QName} ->
precondition_failed("Error finding sharded queue for: ~p", [QName])
end;
intercept(#'queue.delete'{queue = QName} = Method, Content, VHost) ->
case is_sharded(VHost, QName) of
true ->
precondition_failed("Can't delete sharded queue: ~p", [QName]);
_ ->
{Method, Content}
end;
intercept(#'queue.declare'{queue = QName} = Method, Content, VHost) ->
case is_sharded(VHost, QName) of
true ->
%% Since as an interceptor we can't modify what the channel
%% will return, we then modify the queue name so the channel
%% can at least return a queue.declare_ok for that particular
%% queue. Picking the first queue over the others is totally
%% arbitrary.
QName2 = rabbit_sharding_util:make_queue_name(
QName, a2b(node()), 0),
{Method#'queue.declare'{queue = QName2}, Content};
_ ->
{Method, Content}
end;
intercept(#'queue.bind'{queue = QName} = Method, Content, VHost) ->
case is_sharded(VHost, QName) of
true ->
precondition_failed("Can't bind sharded queue: ~p", [QName]);
_ ->
{Method, Content}
end;
intercept(#'queue.unbind'{queue = QName} = Method, Content, VHost) ->
case is_sharded(VHost, QName) of
true ->
precondition_failed("Can't unbind sharded queue: ~p", [QName]);
_ ->
{Method, Content}
end;
intercept(#'queue.purge'{queue = QName} = Method, Content, VHost) ->
case is_sharded(VHost, QName) of
true ->
precondition_failed("Can't purge sharded queue: ~p", [QName]);
_ ->
{Method, Content}
end;
intercept(Method, Content, _VHost) ->
{Method, Content}.
applies_to() ->
['basic.consume', 'basic.get', 'queue.delete', 'queue.declare',
'queue.bind', 'queue.unbind', 'queue.purge'].
%%----------------------------------------------------------------------------
%% If the queue is not part of a shard, return unmodified name
queue_name(VHost, QBin) ->
case lookup_exchange(VHost, QBin) of
{ok, X} ->
case rabbit_sharding_util:shard(X) of
true ->
least_consumers(VHost, QBin, shards_per_node(X));
_ ->
{ok, QBin}
end;
_Error ->
{ok, QBin}
end.
is_sharded(VHost, QBin) ->
case lookup_exchange(VHost, QBin) of
{ok, X} ->
rabbit_sharding_util:shard(X);
_Error ->
false
end.
lookup_exchange(VHost, QBin) ->
rabbit_exchange:lookup(r(VHost, exchange, QBin)).
least_consumers(VHost, QBin, N) ->
F = fun(QNum) ->
QBin2 = rabbit_sharding_util:make_queue_name(
QBin, a2b(node()), QNum),
case consumer_count(r(VHost, queue, QBin2)) of
{error, E} -> {error, E};
[{consumers, C}] -> {C, QBin2}
end
end,
case queues_with_count(F, N) of
[] ->
{error, QBin};
Queues ->
[{_, QBin3} | _ ] = lists:sort(Queues),
{ok, QBin3}
end.
queues_with_count(F, N) ->
lists:foldl(fun (C, Acc) ->
case F(C) of
{error, _} -> Acc;
Ret -> [Ret|Acc]
end
end, [], lists:seq(0, N-1)).
consumer_count(QName) ->
rabbit_amqqueue:with(
QName,
fun(Q) ->
rabbit_amqqueue:info(Q, [consumers])
end).
precondition_failed(Format, QName) ->
protocol_error(precondition_failed, Format, QName).
|
