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rabbit_quorum_queue: Shrink batches of QQs in parallel #15081

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rabbit_quorum_queue: Shrink batches of QQs in parallel #15081

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81 changes: 47 additions & 34 deletions deps/rabbit/src/rabbit_quorum_queue.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -1513,40 +1513,53 @@ delete_member(Q, Node) when ?amqqueue_is_quorum(Q) ->
{ok, pos_integer()} | {error, pos_integer(), term()}}].
shrink_all(Node) ->
?LOG_INFO("Asked to remove all quorum queue replicas from node ~ts", [Node]),
[begin
QName = amqqueue:get_name(Q),
?LOG_INFO("~ts: removing member (replica) on node ~w",
[rabbit_misc:rs(QName), Node]),
Size = length(get_nodes(Q)),
case delete_member(Q, Node) of
ok ->
{QName, {ok, Size-1}};
{error, cluster_change_not_permitted} ->
%% this could be timing related and due to a new leader just being
%% elected but it's noop command not been committed yet.
%% lets sleep and retry once
?LOG_INFO("~ts: failed to remove member (replica) on node ~w "
"as cluster change is not permitted. "
"retrying once in 500ms",
[rabbit_misc:rs(QName), Node]),
timer:sleep(500),
case delete_member(Q, Node) of
ok ->
{QName, {ok, Size-1}};
{error, Err} ->
?LOG_WARNING("~ts: failed to remove member (replica) on node ~w, error: ~w",
[rabbit_misc:rs(QName), Node, Err]),
{QName, {error, Size, Err}}
end;
{error, Err} ->
?LOG_WARNING("~ts: failed to remove member (replica) on node ~w, error: ~w",
[rabbit_misc:rs(QName), Node, Err]),
{QName, {error, Size, Err}}
end
end || Q <- rabbit_amqqueue:list(),
amqqueue:get_type(Q) == ?MODULE,
lists:member(Node, get_nodes(Q))].

Parent = self(),
%% This operation is mostly bound by I/O so this default is set high:
Size = application:get_env(rabbit, quorum_queue_shrink_batch_size, 64),
Chunks = ra_lib:lists_chunk(Size, [Q || Q <- rabbit_amqqueue:list(),
amqqueue:get_type(Q) == ?MODULE,
lists:member(Node, get_nodes(Q))]),
lists:append([begin
Running = [spawn(fun() ->
Res = shrink(Node, Q),
Parent ! {self(), Res}
end) || Q <- Chunk],
[receive
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@michaelklishin michaelklishin Dec 5, 2025

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We should introduce a timeout here. All timeout defaults are wrong but something like 10s or 15s won't suffer from false positives much but avoids blocking the parent process.

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@the-mikedavis the-mikedavis Dec 5, 2025

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Yeah, I wonder if we should also spawn_monitor and look for 'DOWN's as well. I haven't seen this code crash before but it wouldn't hurt to catch exits and avoid this list comprehension getting stuck

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@michaelklishin michaelklishin Dec 5, 2025

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That would be even better. Both are just typical defensive techniques.

{Pid, Res} ->
Res
end || Pid <- Running]
end || Chunk <- Chunks]).

shrink(Node, Q) ->
QName = amqqueue:get_name(Q),
?LOG_INFO("~ts: removing member (replica) on node ~w",
[rabbit_misc:rs(QName), Node]),
Size = length(get_nodes(Q)),
case delete_member(Q, Node) of
ok ->
{QName, {ok, Size-1}};
{error, cluster_change_not_permitted} ->
%% this could be timing related and due to a new leader just being
%% elected but it's noop command not been committed yet.
%% lets sleep and retry once
?LOG_INFO("~ts: failed to remove member (replica) on node ~w "
"as cluster change is not permitted. "
"retrying once in 500ms",
[rabbit_misc:rs(QName), Node]),
timer:sleep(500),
case delete_member(Q, Node) of
ok ->
{QName, {ok, Size-1}};
{error, Err} ->
?LOG_WARNING("~ts: failed to remove member (replica) on node ~w, error: ~w",
[rabbit_misc:rs(QName), Node, Err]),
{QName, {error, Size, Err}}
end;
{error, Err} ->
?LOG_WARNING("~ts: failed to remove member (replica) on node ~w, error: ~w",
[rabbit_misc:rs(QName), Node, Err]),
{QName, {error, Size, Err}}
end.

grow(Node, VhostSpec, QueueSpec, Strategy) ->
grow(Node, VhostSpec, QueueSpec, Strategy, promotable).
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