emit_queue_info - report non-running leaders

Author: mkuratczyk

deps/rabbitmq_prometheus/src/collectors/prometheus_rabbitmq_core_metrics_collector.erl

@@ -417,12 +417,34 @@ identity_info(Endpoint) ->
         }]
     }.
 
-has_leader_running_locally(Q) when is_pid(Q) ->
-    node(Q) =:= node() andalso is_process_alive(Q);
-has_leader_running_locally({Name, Node}) when Node =:= node() ->
-    is_process_alive(whereis(Name));
-has_leader_running_locally(_) ->
-    false.
+membership(Pid, Members) when is_pid(Pid) ->
+    case node(Pid) =:= node() of
+        true ->
+            case is_process_alive(Pid) of
+                true -> leader;
+                false -> undefined
+            end;
+        false ->
+            case lists:member(node(), Members) of
+                true -> follower;
+                false -> not_a_member
+            end
+    end;
+membership({Name, Node}, Members) ->
+    case Node =:= node() of
+        true ->
+            case is_process_alive(whereis(Name)) of
+                true -> leader;
+                false -> undefined
+            end;
+        false ->
+            case lists:member(node(), Members) of
+                true -> follower;
+                false -> not_a_member
+            end
+    end;
+membership(_, _Members) ->
+    undefined.
 
 emit_queue_info(Prefix, VHostsFilter, Callback) ->
     Help = <<"A metric with a constant '1' value and labels that provide some queue details">>,
@@ -434,20 +456,18 @@ emit_queue_info(Prefix, VHostsFilter, Callback) ->
                            false ->
                                Type = amqqueue:get_type(Q),
                                TypeState = amqqueue:get_type_state(Q),
-                               QInfo0 = [{vhost, VHost}, {queue, Name}, {queue_type, Type}],
                                Members = maps:get(nodes, TypeState, []),
-                               case {has_leader_running_locally(amqqueue:get_pid(Q)),
-                                     lists:member(node(), Members)} of
-                                   {true, _} ->
-                                       QInfo = [{membership, leader} | QInfo0],
-                                       [{QInfo, 1}|Acc];
-                                   {false, true} ->
-                                       %% replicated queue with a non-leader member on this node
-                                       QInfo = [{membership, follower} | QInfo0],
-                                       [{QInfo, 1}|Acc];
-                                   _ ->
-                                       %% ignore queues with no local members
-                                       Acc
+                               case membership(amqqueue:get_pid(Q), Members) of
+                                   not_a_member ->
+                                       Acc;
+                                   Membership ->
+                                       QInfo = [
+                                                {vhost, VHost},
+                                                {queue, Name},
+                                                {queue_type, Type},
+                                                {membership, Membership}
+                                               ],
+                                       [{QInfo, 1}|Acc]
                                end
                        end
                end, [], rabbit_amqqueue:list()),