From 66b7ac4c45d833f25ce688402f1309096f7eea45 Mon Sep 17 00:00:00 2001
From: Andrew Mayorov <encube.ul@gmail.com>
Date: Mon, 13 May 2024 21:25:00 +0200
Subject: [PATCH] fix(sessds): persist $SYS messages as well

Otherwise, persistent sessions will not be able to receive $SYS messages
whatsoever.
---
 apps/emqx/src/emqx_persistent_message.erl     |  2 +-
 .../test/emqx_persistent_session_SUITE.erl    | 53 ++++++++++++++++---
 2 files changed, 47 insertions(+), 8 deletions(-)

diff --git a/apps/emqx/src/emqx_persistent_message.erl b/apps/emqx/src/emqx_persistent_message.erl
index c909c5c5f..dc991619b 100644
--- a/apps/emqx/src/emqx_persistent_message.erl
+++ b/apps/emqx/src/emqx_persistent_message.erl
@@ -110,7 +110,7 @@ persist(Msg) ->
     ).
 
 needs_persistence(Msg) ->
-    not (emqx_message:get_flag(dup, Msg) orelse emqx_message:is_sys(Msg)).
+    not emqx_message:get_flag(dup, Msg).
 
 -spec store_message(emqx_types:message()) -> emqx_ds:store_batch_result().
 store_message(Msg) ->
diff --git a/apps/emqx/test/emqx_persistent_session_SUITE.erl b/apps/emqx/test/emqx_persistent_session_SUITE.erl
index 674e1a8d9..f0b783250 100644
--- a/apps/emqx/test/emqx_persistent_session_SUITE.erl
+++ b/apps/emqx/test/emqx_persistent_session_SUITE.erl
@@ -27,6 +27,7 @@
 -compile(nowarn_export_all).
 
 -define(PERSISTENT_MESSAGE_DB, emqx_persistent_message).
+-define(EMQX_CONFIG, "sys_topics.sys_heartbeat_interval = 1s\n").
 
 %%--------------------------------------------------------------------
 %% SUITE boilerplate
@@ -66,19 +67,20 @@ groups() ->
 
 init_per_group(persistence_disabled, Config) ->
     [
-        {emqx_config, "session_persistence { enable = false }"},
+        {emqx_config, ?EMQX_CONFIG ++ "session_persistence { enable = false }"},
         {persistence, false}
         | Config
     ];
 init_per_group(persistence_enabled, Config) ->
     [
         {emqx_config,
-            "session_persistence {\n"
-            "  enable = true\n"
-            "  last_alive_update_interval = 100ms\n"
-            "  renew_streams_interval = 100ms\n"
-            "  session_gc_interval = 2s\n"
-            "}"},
+            ?EMQX_CONFIG ++
+                "session_persistence {\n"
+                "  enable = true\n"
+                "  last_alive_update_interval = 100ms\n"
+                "  renew_streams_interval = 100ms\n"
+                "  session_gc_interval = 2s\n"
+                "}"},
         {persistence, ds}
         | Config
     ];
@@ -1334,6 +1336,43 @@ do_t_will_message(Config, Opts) ->
     ),
     ok.
 
+t_sys_message_delivery(Config) ->
+    ConnFun = ?config(conn_fun, Config),
+    SysTopicFilter = emqx_topic:join(["$SYS", "brokers", '+', "uptime"]),
+    SysTopic = emqx_topic:join(["$SYS", "brokers", atom_to_list(node()), "uptime"]),
+    ClientId = ?config(client_id, Config),
+
+    {ok, Client1} = emqtt:start_link([
+        {clientid, ClientId},
+        {proto_ver, v5},
+        {properties, #{'Session-Expiry-Interval' => 30}}
+        | Config
+    ]),
+    {ok, _} = emqtt:ConnFun(Client1),
+    {ok, _, [1]} = emqtt:subscribe(Client1, SysTopicFilter, [{qos, 1}, {rh, 2}]),
+    ?assertMatch(
+        [
+            #{topic := SysTopic, qos := 0, retain := false, payload := _Uptime1},
+            #{topic := SysTopic, qos := 0, retain := false, payload := _Uptime2}
+        ],
+        receive_messages(2)
+    ),
+
+    ok = emqtt:disconnect(Client1),
+
+    {ok, Client2} = emqtt:start_link([
+        {clientid, ClientId},
+        {proto_ver, v5},
+        {properties, #{'Session-Expiry-Interval' => 30}},
+        {clean_start, false}
+        | Config
+    ]),
+    {ok, _} = emqtt:ConnFun(Client2),
+    ?assertMatch(
+        [#{topic := SysTopic, qos := 0, retain := false, payload := _Uptime3}],
+        receive_messages(1)
+    ).
+
 get_topicwise_order(Msgs) ->
     maps:groups_from_list(fun get_msgpub_topic/1, fun get_msgpub_payload/1, Msgs).