From 522302fee1c7817049715a200e102a44ded1aa94 Mon Sep 17 00:00:00 2001
From: Andrew Mayorov <encube.ul@gmail.com>
Date: Mon, 9 Oct 2023 15:42:36 +0700
Subject: [PATCH] fix(cm): bring back pre-v5.3.0 compat in
 `takeover_session_begin/1`

Which was accidentally broken in bf164175.
---
 apps/emqx/src/emqx_cm.erl                | 15 +++++++++++----
 apps/emqx/src/proto/emqx_cm_proto_v2.erl |  4 +++-
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/apps/emqx/src/emqx_cm.erl b/apps/emqx/src/emqx_cm.erl
index cea22652d..1e4940965 100644
--- a/apps/emqx/src/emqx_cm.erl
+++ b/apps/emqx/src/emqx_cm.erl
@@ -298,9 +298,9 @@ takeover_session_begin(ClientId) ->
 
 takeover_session_begin(ClientId, ChanPid) when is_pid(ChanPid) ->
     case takeover_session(ClientId, ChanPid) of
-        {living, ConnMod, Session} ->
+        {living, ConnMod, ChanPid, Session} ->
             {ok, Session, {ConnMod, ChanPid}};
-        none ->
+        _ ->
             none
     end;
 takeover_session_begin(_ClientId, undefined) ->
@@ -368,13 +368,20 @@ do_takeover_begin(ClientId, ChanPid) when node(ChanPid) == node() ->
         ConnMod when is_atom(ConnMod) ->
             case request_stepdown({takeover, 'begin'}, ConnMod, ChanPid) of
                 {ok, Session} ->
-                    {living, ConnMod, Session};
+                    {living, ConnMod, ChanPid, Session};
                 {error, Reason} ->
                     error(Reason)
             end
     end;
 do_takeover_begin(ClientId, ChanPid) ->
-    wrap_rpc(emqx_cm_proto_v2:takeover_session(ClientId, ChanPid)).
+    case wrap_rpc(emqx_cm_proto_v2:takeover_session(ClientId, ChanPid)) of
+        %% NOTE: v5.3.0
+        {living, ConnMod, Session} ->
+            {living, ConnMod, ChanPid, Session};
+        %% NOTE: other versions
+        Res ->
+            Res
+    end.
 
 %% @doc Discard all the sessions identified by the ClientId.
 -spec discard_session(emqx_types:clientid()) -> ok.
diff --git a/apps/emqx/src/proto/emqx_cm_proto_v2.erl b/apps/emqx/src/proto/emqx_cm_proto_v2.erl
index 29dec50cd..6ccf596c3 100644
--- a/apps/emqx/src/proto/emqx_cm_proto_v2.erl
+++ b/apps/emqx/src/proto/emqx_cm_proto_v2.erl
@@ -65,8 +65,10 @@ get_chann_conn_mod(ClientId, ChanPid) ->
 
 -spec takeover_session(emqx_types:clientid(), emqx_cm:chan_pid()) ->
     none
-    | {expired | persistent, emqx_session:session()}
     | {living, _ConnMod :: atom(), emqx_cm:chan_pid(), emqx_session:session()}
+    %% NOTE: v5.3.0
+    | {living, _ConnMod :: atom(), emqx_session:session()}
+    | {expired | persistent, emqx_session:session()}
     | {badrpc, _}.
 takeover_session(ClientId, ChanPid) ->
     rpc:call(node(ChanPid), emqx_cm, takeover_session, [ClientId, ChanPid], ?T_TAKEOVER * 2).