An alternative to #10415, closes #10330

Per discussion in #10415, this introduces a new module,
rabbit_mgmt_nodes, which provides a couple of helpers
that can be used to implement Cowboy REST's
resource_exists/2 in the modules that return
information about cluster members.

(cherry picked from commit 0c0e2ca932)

deps/rabbitmq_management/app.bzl

@@ -29,6 +29,7 @@ def all_beam_files(name = "all_beam_files"):
             "src/rabbit_mgmt_hsts.erl",
             "src/rabbit_mgmt_load_definitions.erl",
             "src/rabbit_mgmt_login.erl",
+            "src/rabbit_mgmt_nodes.erl",
             "src/rabbit_mgmt_oauth_bootstrap.erl",
             "src/rabbit_mgmt_reset_handler.erl",
             "src/rabbit_mgmt_stats.erl",
@@ -159,6 +160,7 @@ def all_test_beam_files(name = "all_test_beam_files"):
             "src/rabbit_mgmt_hsts.erl",
             "src/rabbit_mgmt_load_definitions.erl",
             "src/rabbit_mgmt_login.erl",
+            "src/rabbit_mgmt_nodes.erl",
             "src/rabbit_mgmt_oauth_bootstrap.erl",
             "src/rabbit_mgmt_reset_handler.erl",
             "src/rabbit_mgmt_stats.erl",
@@ -378,6 +380,7 @@ def all_srcs(name = "all_srcs"):
             "src/rabbit_mgmt_hsts.erl",
             "src/rabbit_mgmt_load_definitions.erl",
             "src/rabbit_mgmt_login.erl",
+            "src/rabbit_mgmt_nodes.erl",
             "src/rabbit_mgmt_oauth_bootstrap.erl",
             "src/rabbit_mgmt_reset_handler.erl",
             "src/rabbit_mgmt_stats.erl",

deps/rabbitmq_management/priv/www/api/index.html

@@ -216,10 +216,17 @@ vary: accept, accept-encoding, origin</pre>
         <td></td>
         <td class="path">/api/nodes/<i>name</i></td>
         <td>
-          An individual node in the RabbitMQ cluster. Add
-          "?memory=true" to get memory statistics, and "?binary=true"
-          to get a breakdown of binary memory use (may be expensive if
-          there are many small binaries in the system).
+          Returns information about an individual node in the RabbitMQ cluster.
+        </td>
+      </tr>
+      <tr>
+        <td>X</td>
+        <td></td>
+        <td></td>
+        <td></td>
+        <td class="path">/api/nodes/<i>name</i>/memory</td>
+        <td>
+          Returns a <a href="https://rabbitmq.com/memory-use.html">memory usage breakdown</a> of an individual node in the RabbitMQ cluster.
         </td>
       </tr>
       <tr>

deps/rabbitmq_management/src/rabbit_mgmt_nodes.erl

@@ -0,0 +1,26 @@
+%% 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) 2007-2024 Broadcom. All Rights Reserved. The term “Broadcom” refers to Broadcom Inc. and/or its subsidiaries. All rights reserved.
+%%
+
+-module(rabbit_mgmt_nodes).
+
+-export([
+    node_name_from_req/1,
+    node_exists/1
+]).
+
+%%
+%% API
+%%
+
+node_name_from_req(ReqData) ->
+    list_to_atom(binary_to_list(rabbit_mgmt_util:id(node, ReqData))).
+
+%% To be used in resource_exists/2
+node_exists(ReqData) ->
+    Node = node_name_from_req(ReqData),
+    AllNodes = rabbit_nodes:list_members(),
+    lists:member(Node, AllNodes).

deps/rabbitmq_management/src/rabbit_mgmt_wm_node.erl

@@ -26,10 +26,7 @@ content_types_provided(ReqData, Context) ->
    {rabbit_mgmt_util:responder_map(to_json), ReqData, Context}.
 
 resource_exists(ReqData, Context) ->
-    {case node0(ReqData) of
-         not_found -> false;
-         _         -> true
-     end, ReqData, Context}.
+    {rabbit_mgmt_nodes:node_exists(ReqData), ReqData, Context}.
 
 to_json(ReqData, Context) ->
     rabbit_mgmt_util:reply(node0(ReqData), ReqData, Context).

deps/rabbitmq_management/src/rabbit_mgmt_wm_node_memory.erl

@@ -26,7 +26,7 @@ content_types_provided(ReqData, Context) ->
    {rabbit_mgmt_util:responder_map(to_json), ReqData, Context}.
 
 resource_exists(ReqData, Context) ->
-    {node_exists(ReqData, get_node(ReqData)), ReqData, Context}.
+    {rabbit_mgmt_nodes:node_exists(ReqData), ReqData, Context}.
 
 to_json(ReqData, {Mode, Context}) ->
     rabbit_mgmt_util:reply(augment(Mode, ReqData), ReqData, {Mode, Context}).
@@ -39,16 +39,9 @@ is_authorized(ReqData, {Mode, Context}) ->
 get_node(ReqData) ->
     list_to_atom(binary_to_list(rabbit_mgmt_util:id(node, ReqData))).
 
-node_exists(ReqData, Node) ->
-    case [N || N <- rabbit_mgmt_wm_nodes:all_nodes(ReqData),
-               proplists:get_value(name, N) == Node] of
-        [] -> false;
-        [_] -> true
-    end.
-
 augment(Mode, ReqData) ->
     Node = get_node(ReqData),
-    case node_exists(ReqData, Node) of
+    case rabbit_mgmt_nodes:node_exists(ReqData) of
         false ->
             not_found;
         true ->

deps/rabbitmq_management/src/rabbit_mgmt_wm_node_memory_ets.erl

@@ -26,7 +26,7 @@ content_types_provided(ReqData, Context) ->
    {rabbit_mgmt_util:responder_map(to_json), ReqData, Context}.
 
 resource_exists(ReqData, Context) ->
-    {node_exists(ReqData, get_node(ReqData)), ReqData, Context}.
+    {rabbit_mgmt_nodes:node_exists(ReqData), ReqData, Context}.
 
 to_json(ReqData, {Mode, Context}) ->
     rabbit_mgmt_util:reply(augment(Mode, ReqData), ReqData, {Mode, Context}).

deps/rabbitmq_management/test/rabbit_mgmt_http_SUITE.erl

@@ -322,6 +322,7 @@ nodes_test(Config) ->
     assert_list([DiscNode], http_get(Config, "/nodes")),
     assert_list([DiscNode], http_get(Config, "/nodes", "monitor", "monitor", ?OK)),
     http_get(Config, "/nodes", "user", "user", ?NOT_AUTHORISED),
+    http_get(Config, "/nodes/does-not-exist", ?NOT_FOUND),
     [Node] = http_get(Config, "/nodes"),
     Path = "/nodes/" ++ binary_to_list(maps:get(name, Node)),
     assert_item(DiscNode, http_get(Config, Path, ?OK)),

moduleindex.yaml

@@ -848,6 +848,7 @@ rabbitmq_management:
 - rabbit_mgmt_hsts
 - rabbit_mgmt_load_definitions
 - rabbit_mgmt_login
+- rabbit_mgmt_nodes
 - rabbit_mgmt_oauth_bootstrap
 - rabbit_mgmt_reset_handler
 - rabbit_mgmt_stats