From 4dc63b26a8ca004ac85c7352cc35c988cff9bb6b Mon Sep 17 00:00:00 2001
From: William Yang <mscame@gmail.com>
Date: Mon, 4 Oct 2021 15:03:14 +0200
Subject: [PATCH] feat(olp): metrics

---
 apps/emqx/src/emqx_connection.erl      |  1 +
 apps/emqx/src/emqx_metrics.erl         | 18 +++++++++++++++++-
 apps/emqx/src/emqx_olp.erl             | 12 ++++++++++--
 apps/emqx/src/emqx_quic_connection.erl |  1 +
 4 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/apps/emqx/src/emqx_connection.erl b/apps/emqx/src/emqx_connection.erl
index 180747208..57c68510f 100644
--- a/apps/emqx/src/emqx_connection.erl
+++ b/apps/emqx/src/emqx_connection.erl
@@ -325,6 +325,7 @@ recvloop(Parent, State = #state{idle_timeout = IdleTimeout}) ->
         IdleTimeout + 100 ->
             case emqx_olp:is_overloaded() of
                 true ->
+                    emqx_metrics:inc('olp.hbn'),
                     recvloop(Parent, State);
                 false ->
                     hibernate(Parent, cancel_stats_timer(State))
diff --git a/apps/emqx/src/emqx_metrics.erl b/apps/emqx/src/emqx_metrics.erl
index 282b8b5f3..8b79f9ff2 100644
--- a/apps/emqx/src/emqx_metrics.erl
+++ b/apps/emqx/src/emqx_metrics.erl
@@ -184,6 +184,15 @@
          {counter, 'session.terminated'}
         ]).
 
+%% Overload protetion counters
+-define(OLP_METRICS,
+        [{counter, 'olp.delay.ok'},
+         {counter, 'olp.delay.timeout'},
+         {counter, 'olp.hbn'},
+         {counter, 'olp.gc'},
+         {counter, 'olp.close.quic'}
+        ]).
+
 -record(state, {next_idx = 1}).
 
 -record(metric, {name, type, idx}).
@@ -430,7 +439,8 @@ init([]) ->
                             ?MESSAGE_METRICS,
                             ?DELIVERY_METRICS,
                             ?CLIENT_METRICS,
-                            ?SESSION_METRICS
+                            ?SESSION_METRICS,
+                            ?OLP_METRICS
                            ]),
     % Store reserved indices
     ok = lists:foreach(fun({Type, Name}) ->
@@ -571,5 +581,11 @@ reserved_idx('session.takeovered')           -> 222;
 reserved_idx('session.discarded')            -> 223;
 reserved_idx('session.terminated')           -> 224;
 
+reserved_idx('olp.delay.ok')                 -> 300;
+reserved_idx('olp.delay.timeout')            -> 301;
+reserved_idx('olp.hbn')                      -> 302;
+reserved_idx('olp.gc')                       -> 303;
+reserved_idx('olp.close.quic')               -> 304;
+
 reserved_idx(_)                              -> undefined.
 
diff --git a/apps/emqx/src/emqx_olp.erl b/apps/emqx/src/emqx_olp.erl
index 758c2d348..2e3efe080 100644
--- a/apps/emqx/src/emqx_olp.erl
+++ b/apps/emqx/src/emqx_olp.erl
@@ -32,12 +32,20 @@
 is_overloaded() ->
   load_ctl:is_overloaded().
 
--spec backoff(Zone :: atom()) -> ok | timeout.
+-spec backoff(Zone :: atom()) -> ok | false | timeout.
 backoff(Zone) ->
   case emqx_config:get_zone_conf(Zone, [overload_protection, enable], false) of
     true ->
       Delay = emqx_config:get_zone_conf(Zone, [overload_protection, backoff_delay], 1),
-      load_ctl:maydelay(Delay);
+      case load_ctl:maydelay(Delay) of
+        false -> false;
+        ok ->
+          emqx_metrics:inc('olp.delay.ok'),
+          ok;
+        timeout ->
+          emqx_metrics:inc('olp.delay.timeout'),
+          timeout
+      end;
     false ->
       ok
   end.
diff --git a/apps/emqx/src/emqx_quic_connection.erl b/apps/emqx/src/emqx_quic_connection.erl
index eb16b9b0a..aaf7321dd 100644
--- a/apps/emqx/src/emqx_quic_connection.erl
+++ b/apps/emqx/src/emqx_quic_connection.erl
@@ -46,6 +46,7 @@ new_conn(Conn, S) ->
                     {error, stream_accept_error}
             end;
         true ->
+            emqx_metrics:inc('olp.close.quic'),
             {error, overloaded}
     end.