From e145fdbef39014ed6f1ceca25639642276648ae2 Mon Sep 17 00:00:00 2001
From: ieQu1 <99872536+ieQu1@users.noreply.github.com>
Date: Thu, 7 Jul 2022 10:46:03 +0200
Subject: [PATCH] fix(shared_sub): Fix crash on dispatch with subscribers
 disconnected

---
 src/emqx.appup.src      | 14 ++++++++++----
 src/emqx_shared_sub.erl |  4 ++--
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/emqx.appup.src b/src/emqx.appup.src
index 2534585eb..db9818c07 100644
--- a/src/emqx.appup.src
+++ b/src/emqx.appup.src
@@ -1,9 +1,12 @@
 %% -*- mode: erlang -*-
 %% Unless you know what you are doing, DO NOT edit manually!!
 {VSN,
-  [{"4.3.17",[{load_module,emqx_access_control,brutal_purge,soft_purge,[]}]},
+  [{"4.3.17",
+    [{load_module,emqx_shared_sub,brutal_purge,soft_purge,[]},
+     {load_module,emqx_access_control,brutal_purge,soft_purge,[]}]},
    {"4.3.16",
-    [{load_module,emqx_access_control,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_shared_sub,brutal_purge,soft_purge,[]},
+     {load_module,emqx_access_control,brutal_purge,soft_purge,[]},
      {load_module,emqx_plugins,brutal_purge,soft_purge,[]},
      {load_module,emqx_metrics,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]},
@@ -652,9 +655,12 @@
      {load_module,emqx_message,brutal_purge,soft_purge,[]},
      {load_module,emqx_limiter,brutal_purge,soft_purge,[]}]},
    {<<".*">>,[]}],
-  [{"4.3.17",[{load_module,emqx_access_control,brutal_purge,soft_purge,[]}]},
+  [{"4.3.17",
+    [{load_module,emqx_shared_sub,brutal_purge,soft_purge,[]},
+     {load_module,emqx_access_control,brutal_purge,soft_purge,[]}]},
    {"4.3.16",
-    [{load_module,emqx_access_control,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_shared_sub,brutal_purge,soft_purge,[]},
+     {load_module,emqx_access_control,brutal_purge,soft_purge,[]},
      {load_module,emqx_plugins,brutal_purge,soft_purge,[]},
      {load_module,emqx_metrics,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]},
diff --git a/src/emqx_shared_sub.erl b/src/emqx_shared_sub.erl
index c7fb1a3cb..1e77b6014 100644
--- a/src/emqx_shared_sub.erl
+++ b/src/emqx_shared_sub.erl
@@ -242,7 +242,7 @@ maybe_nack_dropped(Msg) ->
 
         %% For fresh Ref we send a nack and return true, to note that the inflight is full
         {Sender, {fresh, _Group, Ref}}   -> nack(Sender, Ref, dropped), drop;
-        
+
         %% For retry Ref we can't reject a message if inflight is full, so we mark it as
         %% acknowledged and put it into mqueue
         {_Sender, {retry, _Group, _Ref}} -> maybe_ack(Msg), store;
@@ -311,7 +311,7 @@ do_pick(Strategy, ClientId, SourceTopic, Group, Topic, FailedSubs) ->
             false;
         [] ->
             %% We try redispatch to subs who dropped the message because inflight was full.
-            Found = maps_find_by(FailedSubs, fun({SubPid, FailReason}) ->
+            Found = maps_find_by(FailedSubs, fun(SubPid, FailReason) ->
                 FailReason == dropped andalso is_alive_sub(SubPid)
             end),
             case Found of