rabbitmq-queues: a command to display a member with highest (commit, log, snapshot) index

deps/rabbit/src/rabbit_quorum_queue.erl

@@ -68,6 +68,8 @@
          notify_decorators/3,
          spawn_notify_decorators/3]).
 
+-export([get_member_with_highest_index/3]).
+
 -export([is_enabled/0,
          is_compatible/3,
          declare/2,
@@ -1245,7 +1247,7 @@ key_metrics_rpc(ServerId) ->
     Metrics = ra:key_metrics(ServerId),
     Metrics#{machine_version => rabbit_fifo:version()}.
 
--spec status(rabbit_types:vhost(), Name :: rabbit_misc:resource_name()) ->
+-spec status(rabbit_types:vhost(), rabbit_misc:resource_name()) ->
     [[{binary(), term()}]] | {error, term()}.
 status(Vhost, QueueName) ->
     %% Handle not found queues
@@ -1335,6 +1337,38 @@ get_sys_status(Proc) ->
 
     end.
 
+-spec get_member_with_highest_index(rabbit_types:vhost(), rabbit_misc:resource_name(), atom()) ->
+    [[{binary(), term()}]] | {error, term()}.
+get_member_with_highest_index(Vhost, QueueName, IndexName) ->
+    case ?MODULE:status(Vhost, QueueName) of
+        Status when is_list(Status) ->
+            IndexNameInternal = rabbit_data_coercion:to_atom(IndexName),
+            case index_name_to_status_key(IndexNameInternal) of
+                Key when is_binary(Key) ->
+                    {_HighestIndexValue, HighestEntry} =
+                        lists:foldl(
+                            fun(Entry, {PreviousIndexValue, _PreviousEntry} = Acc) ->
+                                case rabbit_misc:pget(Key, Entry) of
+                                    CurrentIndexValue when is_integer(CurrentIndexValue),
+                                                           CurrentIndexValue > PreviousIndexValue ->
+                                        {CurrentIndexValue, Entry};
+                                    _ ->
+                                        Acc
+                                end
+                            end, {-100, []}, Status),
+                    [HighestEntry];
+                undefined ->
+                    []
+            end;
+        {error, _} = Error ->
+            Error
+    end.
+
+index_name_to_status_key(I) when I =:= commit;   I =:= commit_index   -> <<"Commit Index">>;
+index_name_to_status_key(I) when I =:= log;      I =:= log_index      -> <<"Last Log Index">>;
+index_name_to_status_key(I) when I =:= snapshot; I =:= snapshot_index -> <<"Snapshot Index">>;
+index_name_to_status_key(_I) -> undefined.
+
 add_member(VHost, Name, Node, Membership, Timeout)
   when is_binary(VHost) andalso
        is_binary(Name) andalso

deps/rabbit/test/quorum_queue_SUITE.erl

@@ -115,7 +115,8 @@ groups() ->
                                             node_removal_is_not_quorum_critical,
                                             select_nodes_with_least_replicas,
                                             select_nodes_with_least_replicas_node_down,
-                                            subscribe_from_each
+                                            subscribe_from_each,
+                                            get_member_with_highest_index
 
 
                                            ]},
@@ -365,6 +366,8 @@ init_per_testcase(Testcase, Config) ->
             {skip, "peek_with_wrong_queue_type isn't mixed versions compatible"};
         cancel_consumer_gh_3729 when IsMixed andalso RabbitMQ3 ->
             {skip, "this test is not compatible with RabbitMQ 3.13.x"};
+        get_member_with_highest_index when IsMixed ->
+            {skip, "get_member_with_highest_index isn't mixed versions compatible"};
         _ ->
             Config1 = rabbit_ct_helpers:testcase_started(Config, Testcase),
             rabbit_ct_broker_helpers:rpc(Config, 0, ?MODULE, delete_queues, []),
@@ -4576,6 +4579,95 @@ leader_health_check(Config) ->
     amqp_connection:close(Conn1),
     amqp_connection:close(Conn2).
 
+get_member_with_highest_index(Config) ->
+    [Node1, Node2, Node3, Node4, Node5] =
+        rabbit_ct_broker_helpers:get_node_configs(Config, nodename),
+
+    Q = ?config(queue_name, Config),
+    VHost = <<"/">>,
+
+    Statuses =
+    %%  [{Node, Member, LogIdx, CommitIdx, SnapshotIdx}, ...]
+        [{Node1, leader,   1015, 1010, 1010}, %% highest SnapshotIdx
+         {Node2, follower, 1015, 1010, 1010}, %% highest SnapshotIdx (duplicate)
+         {Node3, follower, 1013, 1013, 1009}, %% highest CommitIdx
+         {Node4, follower, 1016, 1009, 1008}, %% highest LogIdx
+         {Node5, follower, 1013, 1012, undefined}],
+
+    Term = 1,
+    MachineVersion = 7,
+
+    meck:new(rabbit_quorum_queue, [passthrough, no_link]),
+    meck:expect(
+      rabbit_quorum_queue, status,
+      fun(_, _) ->
+          [[{<<"Node Name">>, Node},
+            {<<"Raft State">>, Member},
+            {<<"Last Log Index">>, LogIndex},
+            {<<"Last Written">>, LogIndex},
+            {<<"Last Applied">>, LogIndex},
+            {<<"Commit Index">>, CommitIndex},
+            {<<"Snapshot Index">>, SnapshotIdx},
+            {<<"Term">>, Term},
+            {<<"Machine Version">>, MachineVersion}]
+                || {Node, Member, LogIndex, CommitIndex, SnapshotIdx} <- Statuses]
+      end),
+
+    ct:pal("quorum status: ~tp", [rabbit_quorum_queue:status(VHost, Q)]),
+
+    ExpectedHighestLogIdx =
+        [[{<<"Node Name">>, Node4},
+          {<<"Raft State">>, follower},
+          {<<"Last Log Index">>, 1016},
+          {<<"Last Written">>,1016},
+          {<<"Last Applied">>,1016},
+          {<<"Commit Index">>, 1009},
+          {<<"Snapshot Index">>, 1008},
+          {<<"Term">>, Term},
+          {<<"Machine Version">>, MachineVersion}]],
+
+    [?assertEqual(ExpectedHighestLogIdx,
+        rabbit_quorum_queue:get_member_with_highest_index(VHost, Q, I)) || I <- [log, log_index]],
+
+    ExpectedHighestCommitIdx =
+        [[{<<"Node Name">>, Node3},
+          {<<"Raft State">>, follower},
+          {<<"Last Log Index">>, 1013},
+          {<<"Last Written">>,1013},
+          {<<"Last Applied">>,1013},
+          {<<"Commit Index">>, 1013},
+          {<<"Snapshot Index">>, 1009},
+          {<<"Term">>, Term},
+          {<<"Machine Version">>, MachineVersion}]],
+
+    [?assertEqual(ExpectedHighestCommitIdx,
+        rabbit_quorum_queue:get_member_with_highest_index(VHost, Q, I)) || I <- [commit, commit_index]],
+
+    ExpectedHighestSnapshotIdx =
+        [[{<<"Node Name">>, Node1},
+          {<<"Raft State">>, leader},
+          {<<"Last Log Index">>, 1015},
+          {<<"Last Written">>,1015},
+          {<<"Last Applied">>,1015},
+          {<<"Commit Index">>, 1010},
+          {<<"Snapshot Index">>, 1010},
+          {<<"Term">>, Term},
+          {<<"Machine Version">>, MachineVersion}]],
+        %  Duplicate:
+        %  [{<<"Node Name">>, Node2},
+        %   {<<"Raft State">>, follower},
+        %   {<<"Last Log Index">>, 1015},
+        %   {<<"Last Written">>,1015},
+        %   {<<"Last Applied">>,1015},
+        %   {<<"Commit Index">>, 1010},
+        %   {<<"Snapshot Index">>, 1010},
+        %   {<<"Term">>, Term},
+        %   {<<"Machine Version">>, MachineVersion}],
+
+    [?assertEqual(ExpectedHighestSnapshotIdx,
+        rabbit_quorum_queue:get_member_with_highest_index(VHost, Q, I)) || I <- [snapshot, snapshot_index]],
+
+    ok.
 
 leader_locator_client_local(Config) ->
     [Server1 | _] = Servers = rabbit_ct_broker_helpers:get_node_configs(Config, nodename),

deps/rabbitmq_cli/lib/rabbitmq/cli/queues/commands/member_with_highest_index.ex

@@ -0,0 +1,73 @@
+## 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) 2007-2025 Broadcom. All Rights Reserved. The term “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.  All rights reserved.
+
+defmodule RabbitMQ.CLI.Queues.Commands.MemberWithHighestIndexCommand do
+  alias RabbitMQ.CLI.Core.DocGuide
+  import RabbitMQ.CLI.Core.DataCoercion
+
+  @behaviour RabbitMQ.CLI.CommandBehaviour
+
+  use RabbitMQ.CLI.Core.AcceptsOnePositionalArgument
+  use RabbitMQ.CLI.Core.RequiresRabbitAppRunning
+
+  def switches(), do: [index: :string, timeout: :integer]
+  def aliases(), do: [i: :index, t: :timeout]
+
+  def merge_defaults(args, opts) do
+    {args, Map.merge(%{vhost: "/", index: "log"}, opts)}
+  end
+
+  def run([name] = _args, %{vhost: vhost, index: index, node: node_name}) do
+    case :rabbit_misc.rpc_call(node_name, :rabbit_quorum_queue, :get_member_with_highest_index, [
+           vhost,
+           name,
+           to_atom(String.downcase(index))
+         ]) do
+      {:error, :classic_queue_not_supported} ->
+        index = format_index(String.downcase(index))
+        {:error, "Cannot get #{index} index from a classic queue"}
+
+      {:error, :not_found} ->
+        {:error, {:not_found, :queue, vhost, name}}
+
+      other ->
+        other
+    end
+  end
+
+  use RabbitMQ.CLI.DefaultOutput
+
+  def formatter(), do: RabbitMQ.CLI.Formatters.PrettyTable
+
+  def usage, do: "member_with_highest_index <queue> [--vhost <vhost>] [--index <commit|commit_index|log|log_index|snapshot|snapshot_index>]"
+
+  def usage_additional do
+    [
+      ["<queue>", "quorum queue name"],
+      ["--index <commit|commit_index|log|log_index|snapshot|snapshot_index>", "name of the index to use to lookup highest member"]
+    ]
+  end
+
+  def usage_doc_guides() do
+    [
+      DocGuide.quorum_queues()
+    ]
+  end
+
+  def help_section, do: :replication
+
+  def description, do: "Look up first member of a quorum queue with the highest commit, log or snapshot index."
+
+  def banner([name], %{node: node, index: index, vhost: vhost}) do
+    index = format_index(String.downcase(index))
+    "Member with highest #{index} index for queue #{name} in vhost #{vhost} on node #{node}..."
+  end
+
+  defp format_index("log_index"), do: "log"
+  defp format_index("commit_index"), do: "commit"
+  defp format_index("snapshot_index"), do: "snapshot"
+  defp format_index(index_name), do: index_name
+end

deps/rabbitmq_cli/test/queues/member_with_highest_index_test.exs

@@ -0,0 +1,55 @@
+## 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) 2007-2025 Broadcom. All Rights Reserved. The term “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.  All rights reserved.
+
+defmodule RabbitMQ.CLI.Queues.Commands.MemberWithHighestIndexCommandTest do
+  use ExUnit.Case, async: false
+  import TestHelper
+
+  @command RabbitMQ.CLI.Queues.Commands.MemberWithHighestIndexCommand
+
+  setup_all do
+    RabbitMQ.CLI.Core.Distribution.start()
+
+    :ok
+  end
+
+  setup context do
+    {:ok,
+     opts: %{
+       node: get_rabbit_hostname(),
+       timeout: context[:test_timeout] || 30000
+     }}
+  end
+
+  test "validate: when no arguments are provided, returns a failure" do
+    assert @command.validate([], %{}) == {:validation_failure, :not_enough_args}
+  end
+
+  test "validate: when two or more arguments are provided, returns a failure" do
+    assert @command.validate(["quorum-queue-a", "one-extra-arg"], %{}) ==
+             {:validation_failure, :too_many_args}
+
+    assert @command.validate(
+             ["quorum-queue-a", "extra-arg", "another-extra-arg"],
+             %{}
+           ) == {:validation_failure, :too_many_args}
+  end
+
+  test "validate: treats one positional arguments and default switches as a success" do
+    assert @command.validate(["quorum-queue-a"], %{}) == :ok
+  end
+
+  @tag test_timeout: 3000
+  test "run: targeting an unreachable node throws a badrpc" do
+    assert match?(
+             {:badrpc, _},
+             @command.run(
+               ["quorum-queue-a"],
+               %{node: :jake@thedog, vhost: "/", index: "log", timeout: 200}
+             )
+           )
+  end
+end