From d88deb9ceb5805da3895f1547c3c5da65815ee6a Mon Sep 17 00:00:00 2001
From: Thales Macedo Garitezi <thalesmg@gmail.com>
Date: Mon, 27 Nov 2023 11:56:35 -0300
Subject: [PATCH] feat(ds): add session timer to bump last alive at timestamp

---
 apps/emqx/src/emqx_persistent_session_ds.erl | 22 ++++++++++++++++----
 apps/emqx/src/emqx_schema.erl                |  8 +++++++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/apps/emqx/src/emqx_persistent_session_ds.erl b/apps/emqx/src/emqx_persistent_session_ds.erl
index 1429d6e97..97825e728 100644
--- a/apps/emqx/src/emqx_persistent_session_ds.erl
+++ b/apps/emqx/src/emqx_persistent_session_ds.erl
@@ -117,6 +117,7 @@
 -type clientinfo() :: emqx_types:clientinfo().
 -type conninfo() :: emqx_session:conninfo().
 -type replies() :: emqx_session:replies().
+-type timer() :: pull | get_streams | bump_last_alive_at.
 
 -define(STATS_KEYS, [
     subscriptions_cnt,
@@ -396,6 +397,11 @@ handle_timeout(
 handle_timeout(_ClientInfo, get_streams, Session) ->
     renew_streams(Session),
     ensure_timer(get_streams),
+    {ok, [], Session};
+handle_timeout(_ClientInfo, bump_last_alive_at, Session0) ->
+    NowMS = now_ms(),
+    Session = session_set_last_alive_at_trans(Session0, NowMS),
+    ensure_timer(bump_last_alive_at),
     {ok, [], Session}.
 
 -spec replay(clientinfo(), [], session()) ->
@@ -553,7 +559,7 @@ session_open(SessionId, NewConnInfo) ->
                     false ->
                         %% new connection being established
                         Record1 = Record0#session{conninfo = NewConnInfo},
-                        Record = session_set_last_alive_at(Record1, never),
+                        Record = session_set_last_alive_at(Record1, NowMS),
                         Session = export_session(Record),
                         DSSubs = session_read_subscriptions(SessionId),
                         Subscriptions = export_subscriptions(DSSubs),
@@ -592,6 +598,10 @@ session_create(SessionId, ConnInfo, Props) ->
     ok = mnesia:write(?SESSION_TAB, Session, write),
     Session.
 
+session_set_last_alive_at_trans(Session, LastAliveAt) ->
+    #{conninfo := ConnInfo} = Session,
+    session_set_last_alive_at_trans(Session, ConnInfo, LastAliveAt).
+
 session_set_last_alive_at_trans(Session, NewConnInfo, LastAliveAt) ->
     #{id := SessionId} = Session,
     transaction(fun() ->
@@ -863,13 +873,17 @@ export_record(_, _, [], Acc) ->
 %% effects. Add `CBM:init' callback to the session behavior?
 ensure_timers() ->
     ensure_timer(pull),
-    ensure_timer(get_streams).
+    ensure_timer(get_streams),
+    ensure_timer(bump_last_alive_at).
 
--spec ensure_timer(pull | get_streams) -> ok.
+-spec ensure_timer(timer()) -> ok.
+ensure_timer(bump_last_alive_at = Type) ->
+    BumpInterval = emqx_config:get([session_persistence, last_alive_update_interval]),
+    ensure_timer(Type, BumpInterval);
 ensure_timer(Type) ->
     ensure_timer(Type, 100).
 
--spec ensure_timer(pull | get_streams, non_neg_integer()) -> ok.
+-spec ensure_timer(timer(), non_neg_integer()) -> ok.
 ensure_timer(Type, Timeout) ->
     _ = emqx_utils:start_timer(Timeout, {emqx_session, Type}),
     ok.
diff --git a/apps/emqx/src/emqx_schema.erl b/apps/emqx/src/emqx_schema.erl
index 5c3f2e72f..e10160e4c 100644
--- a/apps/emqx/src/emqx_schema.erl
+++ b/apps/emqx/src/emqx_schema.erl
@@ -1781,6 +1781,14 @@ fields("session_persistence") ->
                     desc => ?DESC(session_ds_idle_poll_interval)
                 }
             )},
+        {"last_alive_update_interval",
+            sc(
+                timeout_duration(),
+                #{
+                    default => <<"5000ms">>,
+                    desc => ?DESC(session_ds_last_alive_update_interval)
+                }
+            )},
         {"force_persistence",
             sc(
                 boolean(),