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Limit number of unique node names for rabbitmqctl #552

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Merged
merged 1 commit into from
Jan 14, 2016
Merged

Limit number of unique node names for rabbitmqctl #552

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29 changes: 26 additions & 3 deletions src/rabbit_cli.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -45,11 +45,21 @@

-endif.

ensure_cli_distribution() ->
case start_distribution() of
{ok, _} ->
ok;
{error, Error} ->
print_error("Failed to initialize erlang distribution: ~p.",
[Error]),
rabbit_misc:quit(?EX_TEMPFAIL)
end.

%%----------------------------------------------------------------------------

main(ParseFun, DoFun, UsageMod) ->
error_logger:tty(false),
start_distribution(),
ensure_cli_distribution(),
{ok, [[NodeStr|_]|_]} = init:get_argument(nodename),
{Command, Opts, Args} =
case ParseFun(init:get_plain_arguments(), NodeStr) of
Expand Down Expand Up @@ -125,9 +135,22 @@ main(ParseFun, DoFun, UsageMod) ->
rabbit_misc:quit(?EX_SOFTWARE)
end.

start_distribution_anon(0, LastError) ->
{error, LastError};
start_distribution_anon(TriesLeft, _) ->
NameCandidate = list_to_atom(rabbit_misc:format("rabbitmq-cli-~2..0b", [rabbit_misc:random(100)])),
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rabbit_misc:random is undefined.
random:uniform can be used in this case, because it just retries in same process.

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Yeah, you'll need rabbitmq/rabbitmq-common#48
And also you can't simply run ./scripts/rabbitmqctl from rabbitmq-server checkout - rabbit_common will be missing from code path (but on installed server it will be available through rabbit_common.ez archive).

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One can run make package-generic-unix UNOFFICIAL_RELEASE=true from the umbrella to produce a tarball. It should take a couple of minutes.

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Then every sequence of "random" numbers will be the same - and it's exactly the thing that we want to avoid, to reduce contention.

case net_kernel:start([NameCandidate, name_type()]) of
{ok, _} = Result ->
Result;
{error, Reason} ->
start_distribution_anon(TriesLeft - 1, Reason)
end.

%% Tries to start distribution with randonm name choosen from limited list of candidates - to
%% prevent atom table pollution on target nodes.
start_distribution() ->
start_distribution(list_to_atom(
rabbit_misc:format("rabbitmq-cli-~s", [os:getpid()]))).
rabbit_nodes:ensure_epmd(),
start_distribution_anon(10, undefined).

start_distribution(Name) ->
rabbit_nodes:ensure_epmd(),
Expand Down