Merge pull request rabbitmq#6930 from rabbitmq/add-rabbit-is_serving

rabbit: Add `is_serving/{0,1}` function

deps/rabbit/src/rabbit.erl

@@ -15,8 +15,9 @@
 
 -export([start/0, boot/0, stop/0,
          stop_and_halt/0, await_startup/0, await_startup/1, await_startup/3,
-         status/0, is_running/0, alarms/0,
-         is_running/1, environment/0, rotate_logs/0, force_event_refresh/1,
+         status/0, is_running/0, is_serving/0, alarms/0,
+         is_running/1, is_serving/1, environment/0, rotate_logs/0,
+         force_event_refresh/1,
          start_fhc/0]).
 
 -export([start/2, stop/1, prep_stop/1]).
@@ -767,7 +768,42 @@ total_queue_count() ->
                 end,
                 0, rabbit_vhost:list_names()).
 
--spec is_running() -> boolean().
+-spec is_serving() -> IsServing when
+      IsServing :: boolean().
+%% @doc Indicates if this RabbitMQ node is ready to serve clients or not.
+%%
+%% It differs from {@link is_running/0} in the sense that a running RabbitMQ
+%% node could be under maintenance. A serving node is one where RabbitMQ is
+%% running and is not under maintenance currently, thus accepting clients.
+
+is_serving() ->
+    ThisNode = node(),
+    is_running() andalso
+    not rabbit_maintenance:is_being_drained_local_read(ThisNode).
+
+-spec is_serving(Node) -> IsServing when
+      Node :: node(),
+      IsServing :: boolean().
+%% @doc Indicates if the given node is ready to serve client or not.
+
+is_serving(Node) when Node =:= node() ->
+    is_serving();
+is_serving(Node) ->
+    case rpc:call(Node, rabbit, is_serving, []) of
+        true -> true;
+        _    -> false
+    end.
+
+-spec is_running() -> IsRunning when
+      IsRunning :: boolean().
+%% @doc Indicates if the `rabbit' application is running on this RabbitMQ node
+%% or not.
+%%
+%% A RabbitMQ node is considered to run as soon as the `rabbit' application is
+%% running. It means this node participates to the cluster. However, it could
+%% accept or reject clients if it is under maintenance. See {@link
+%% is_serving/0} to check if this node is running and is ready to serve
+%% clients.
 
 is_running() -> is_running(node()).
 

deps/rabbit/test/maintenance_mode_SUITE.erl

@@ -16,11 +16,15 @@
 
 all() ->
     [
+      {group, cluster_size_1},
       {group, cluster_size_3}
     ].
 
 groups() ->
     [
+      {cluster_size_1, [], [
+          is_serving_works
+      ]},
       {cluster_size_3, [], [
           maintenance_mode_status,
           listener_suspension_status,
@@ -40,7 +44,10 @@ init_per_suite(Config) ->
 end_per_suite(Config) ->
     rabbit_ct_helpers:run_teardown_steps(Config).
 
-init_per_group(_Group, Config) ->
+init_per_group(cluster_size_1, Config) ->
+    rabbit_ct_helpers:set_config(Config,
+                                 [{rmq_nodes_count, 1}]);
+init_per_group(cluster_size_3, Config) ->
     rabbit_ct_helpers:set_config(Config,
                                  [{rmq_nodes_count, 3}]).
 
@@ -85,6 +92,38 @@ end_per_testcase(Testcase, Config) ->
 %% Test Cases
 %% -------------------------------------------------------------------
 
+is_serving_works(Config) ->
+    [Node] = rabbit_ct_broker_helpers:get_node_configs(Config, nodename),
+
+    ?assert(rabbit:is_running(Node)),
+    ?assert(rabbit:is_serving(Node)),
+
+    rabbit_ct_broker_helpers:mark_as_being_drained(Config, Node),
+    rabbit_ct_helpers:await_condition(
+        fun () -> rabbit_ct_broker_helpers:is_being_drained_local_read(Config, Node) end,
+        10000),
+
+    ?assert(rabbit:is_running(Node)),
+    ?assertNot(rabbit:is_serving(Node)),
+
+    rabbit_ct_broker_helpers:unmark_as_being_drained(Config, Node),
+    rabbit_ct_helpers:await_condition(
+        fun () -> not rabbit_ct_broker_helpers:is_being_drained_local_read(Config, Node) end,
+        10000),
+
+    ?assert(rabbit:is_running(Node)),
+    ?assert(rabbit:is_serving(Node)),
+
+    rabbit_ct_broker_helpers:stop_broker(Config, Node),
+
+    ?assertNot(rabbit:is_running(Node)),
+    ?assertNot(rabbit:is_serving(Node)),
+
+    rabbit_ct_broker_helpers:start_broker(Config, Node),
+
+    ?assert(rabbit:is_running(Node)),
+    ?assert(rabbit:is_serving(Node)).
+
 maintenance_mode_status(Config) ->
     Nodes = [A, B, C] = rabbit_ct_broker_helpers:get_node_configs(Config, nodename),