From aff1ea5af0048e638945be77e8e12a07ce5d3c75 Mon Sep 17 00:00:00 2001
From: Shawn <506895667@qq.com>
Date: Mon, 28 Jun 2021 09:31:10 +0800
Subject: [PATCH 1/2] fix(shared_sub): failed to clean the
 emqx_shared_subscription tab

---
 src/emqx_shared_sub.erl | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/emqx_shared_sub.erl b/src/emqx_shared_sub.erl
index 71372cd90..4466d0c7f 100644
--- a/src/emqx_shared_sub.erl
+++ b/src/emqx_shared_sub.erl
@@ -325,9 +325,13 @@ handle_info({mnesia_table_event, {write, NewRecord, _}}, State = #state{pmon = P
     #emqx_shared_subscription{subpid = SubPid} = NewRecord,
     {noreply, update_stats(State#state{pmon = emqx_pmon:monitor(SubPid, PMon)})};
 
-handle_info({mnesia_table_event, {delete_object, OldRecord, _}}, State = #state{pmon = PMon}) ->
-    #emqx_shared_subscription{subpid = SubPid} = OldRecord,
-    {noreply, update_stats(State#state{pmon = emqx_pmon:demonitor(SubPid, PMon)})};
+%% The subscriber may have subscribed multiple topics, so we need to keep monitoring the PID until
+%% it `unsubscribed` the last topic.
+%% The trick is we don't demonitor the subscriber here, and (after a long time) it will eventually
+%% be disconnected.
+% handle_info({mnesia_table_event, {delete_object, OldRecord, _}}, State = #state{pmon = PMon}) ->
+%     #emqx_shared_subscription{subpid = SubPid} = OldRecord,
+%     {noreply, update_stats(State#state{pmon = emqx_pmon:demonitor(SubPid, PMon)})};
 
 handle_info({mnesia_table_event, _Event}, State) ->
     {noreply, State};
@@ -337,8 +341,7 @@ handle_info({'DOWN', _MRef, process, SubPid, _Reason}, State = #state{pmon = PMo
     cleanup_down(SubPid),
     {noreply, update_stats(State#state{pmon = emqx_pmon:erase(SubPid, PMon)})};
 
-handle_info(Info, State) ->
-    ?LOG(error, "Unexpected info: ~p", [Info]),
+handle_info(_Info, State) ->
     {noreply, State}.
 
 terminate(_Reason, _State) ->

From 285fdaaa9a930e943586981b71eecc1bea555def Mon Sep 17 00:00:00 2001
From: Shawn <506895667@qq.com>
Date: Mon, 28 Jun 2021 09:32:17 +0800
Subject: [PATCH 2/2] chore(appup): update the appup for 4.2.13

---
 src/emqx.appup.src | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/emqx.appup.src b/src/emqx.appup.src
index f87d3f5c2..3f854286f 100644
--- a/src/emqx.appup.src
+++ b/src/emqx.appup.src
@@ -8,6 +8,9 @@
     end,
 {VSN,
   [
+   {"4.2.12", [
+      {load_module, emqx_shared_sub, soft_purge, soft_purge, []}
+    ]},
    {"4.2.11", [
       {load_module, emqx_router_sup, soft_purge, soft_purge, []},
       {load_module, emqx_broker, soft_purge, soft_purge, []},
@@ -77,6 +80,9 @@
     {<<".*">>, []}
   ],
   [
+   {"4.2.12", [
+      {load_module, emqx_shared_sub, soft_purge, soft_purge, []}
+   ]},
    {"4.2.11", [
       {load_module, emqx_router_sup, soft_purge, soft_purge, []},
       {load_module, emqx_broker, soft_purge, soft_purge, []},