feat(sessds): Add metrics for the number of persisted messages

apps/emqx/src/emqx_metrics.erl

@@ -222,7 +222,9 @@
         % Messages delivered
         {counter, 'messages.delivered'},
         % Messages acked
-        {counter, 'messages.acked'}
+        {counter, 'messages.acked'},
+        % Messages persistently stored
+        {counter, 'messages.persisted'}
     ]
 ).
 
@@ -718,4 +720,5 @@ reserved_idx('overload_protection.gc') -> 403;
 reserved_idx('overload_protection.new_conn') -> 404;
 reserved_idx('messages.validation_succeeded') -> 405;
 reserved_idx('messages.validation_failed') -> 406;
+reserved_idx('messages.persisted') -> 407;
 reserved_idx(_) -> undefined.

apps/emqx/src/emqx_persistent_message.erl

@@ -114,6 +114,7 @@ needs_persistence(Msg) ->
 
 -spec store_message(emqx_types:message()) -> emqx_ds:store_batch_result().
 store_message(Msg) ->
+    emqx_metrics:inc('messages.persisted'),
     emqx_ds:store_batch(?PERSISTENT_MESSAGE_DB, [Msg], #{sync => false}).
 
 has_subscribers(#message{topic = Topic}) ->

apps/emqx_dashboard/include/emqx_dashboard.hrl

@@ -67,7 +67,8 @@
     %, sent_bytes
     validation_succeeded,
     validation_failed,
-    dropped
+    dropped,
+    persisted
 ]).
 
 -define(GAUGE_SAMPLER_LIST, [
@@ -87,7 +88,8 @@
     sent => sent_msg_rate,
     validation_succeeded => validation_succeeded_rate,
     validation_failed => validation_failed_rate,
-    dropped => dropped_msg_rate
+    dropped => dropped_msg_rate,
+    persisted => persisted_rate
 }).
 
 -define(CURRENT_SAMPLE_NON_RATE,

apps/emqx_dashboard/src/emqx_dashboard_monitor.erl

@@ -428,7 +428,8 @@ stats(sent) -> emqx_metrics:val('messages.sent');
 stats(sent_bytes) -> emqx_metrics:val('bytes.sent');
 stats(validation_succeeded) -> emqx_metrics:val('messages.validation_succeeded');
 stats(validation_failed) -> emqx_metrics:val('messages.validation_failed');
-stats(dropped) -> emqx_metrics:val('messages.dropped').
+stats(dropped) -> emqx_metrics:val('messages.dropped');
+stats(persisted) -> emqx_metrics:val('messages.persisted').
 
 %% -------------------------------------------------------------------------------------------------
 %% Retained && License Quota

apps/emqx_dashboard/src/emqx_dashboard_monitor_api.erl

@@ -192,6 +192,8 @@ swagger_desc(validation_succeeded) ->
     swagger_desc_format("Message validations succeeded ");
 swagger_desc(validation_failed) ->
     swagger_desc_format("Message validations failed ");
+swagger_desc(persisted) ->
+    swagger_desc_format("Messages saved to the durable storage ");
 swagger_desc(subscriptions) ->
     <<"Subscriptions at the time of sampling.", ?APPROXIMATE_DESC>>;
 swagger_desc(topics) ->
@@ -218,6 +220,8 @@ swagger_desc(validation_succeeded_rate) ->
     swagger_desc_format("Message validations succeeded ", per);
 swagger_desc(validation_failed_rate) ->
     swagger_desc_format("Message validations failed ", per);
+swagger_desc(persisted_rate) ->
+    swagger_desc_format("Messages saved to the durable storage ", per);
 swagger_desc(retained_msg_count) ->
     <<"Retained messages count at the time of sampling.", ?APPROXIMATE_DESC>>;
 swagger_desc(shared_subscriptions) ->

apps/emqx_prometheus/test/emqx_prometheus_SUITE.erl

@@ -89,7 +89,9 @@ init_per_group(new_config, Config) ->
     Apps = emqx_cth_suite:start(
         [
             %% coverage olp metrics
-            {emqx, "overload_protection.enable = true"},
+            {emqx,
+                "overload_protection.enable = true\n"
+                "session_persistence.enable = true"},
             {emqx_license, "license.key = default"},
             {emqx_prometheus, #{config => config(default)}}
         ],