refactor(cm): rename takeover -> request_stepdown

see: https://github.com/emqx/emqx/pull/7026#pullrequestreview-891954135

apps/emqx_exproto/src/emqx_exproto.appup.src

@@ -1,22 +1,22 @@
 %% -*- mode: erlang -*-
 {VSN,
-  [{<<"4\\.3\\.[4-5]">>,
+  [{<<"4\\.3\\.[4-5]$">>,
     [{load_module,emqx_exproto_channel,brutal_purge,soft_purge,[]}]},
-   {<<"4\\.3\\.[2-3]">>,
+   {<<"4\\.3\\.[2-3]$">>,
     [{load_module,emqx_exproto_conn,brutal_purge,soft_purge,[]},
      {load_module,emqx_exproto_channel,brutal_purge,soft_purge,[]}]},
-   {<<"4\\.3\\.[0-1]">>,
+   {<<"4\\.3\\.[0-1]$">>,
     [{load_module,emqx_exproto_gsvr,brutal_purge,soft_purge,[]},
      {load_module,emqx_exproto_gcli,brutal_purge,soft_purge,[]},
      {load_module,emqx_exproto_conn,brutal_purge,soft_purge,[]},
      {load_module,emqx_exproto_channel,brutal_purge,soft_purge,[]}]},
    {<<".*">>,[]}],
-  [{<<"4\\.3\\.[4-5]">>,
+  [{<<"4\\.3\\.[4-5]$">>,
     [{load_module,emqx_exproto_channel,brutal_purge,soft_purge,[]}]},
-   {<<"4\\.3\\.[2-3]">>,
+   {<<"4\\.3\\.[2-3]$">>,
     [{load_module,emqx_exproto_conn,brutal_purge,soft_purge,[]},
      {load_module,emqx_exproto_channel,brutal_purge,soft_purge,[]}]},
-   {<<"4\\.3\\.[0-1]">>,
+   {<<"4\\.3\\.[0-1]$">>,
     [{load_module,emqx_exproto_gsvr,brutal_purge,soft_purge,[]},
      {load_module,emqx_exproto_gcli,brutal_purge,soft_purge,[]},
      {load_module,emqx_exproto_conn,brutal_purge,soft_purge,[]},

src/emqx_cm.erl

@@ -235,7 +235,7 @@ open_session(false, ClientInfo = #{clientid := ClientId}, ConnInfo) ->
                       case takeover_session(ClientId) of
                           {ok, ConnMod, ChanPid, Session} ->
                               ok = emqx_session:resume(ClientInfo, Session),
-                              case takeover('end', ConnMod, ChanPid) of
+                              case request_stepdown({takeover, 'end'}, ConnMod, ChanPid) of
                                   {ok, Pendings} ->
                                       register_channel(ClientId, Self, ConnInfo),
                                       {ok, #{session  => Session,
@@ -278,7 +278,7 @@ takeover_session(ClientId, ChanPid) when node(ChanPid) == node() ->
         undefined ->
             {error, not_found};
         ConnMod when is_atom(ConnMod) ->
-            case takeover('begin', ConnMod, ChanPid) of
+            case request_stepdown({takeover, 'begin'}, ConnMod, ChanPid) of
                 {ok, Session} ->
                     {ok, ConnMod, ChanPid, Session};
                 {error, Reason} ->
@@ -300,22 +300,22 @@ discard_session(ClientId) when is_binary(ClientId) ->
 %% If failed to response (e.g. timeout) force a kill.
 %% Keeping the stale pid around, or returning error or raise an exception
 %% benefits nobody.
--spec takeover(Action, module(), pid())
+-spec request_stepdown(Action, module(), pid())
     -> ok
      | {ok, emqx_session:session() | list(emqx_type:deliver())}
      | {error, term()}
-  when Action :: kick | discard | 'begin' | 'end'.
+  when Action :: kick | discard | {takeover, 'begin'} | {takeover, 'end'}.
-takeover(Action, ConnMod, Pid) ->
+request_stepdown(Action, ConnMod, Pid) ->
-    {NAction, Timeout} =
+    Timeout =
         case Action == kick orelse Action == discard of
-            true -> {Action, ?T_KICK};
+            true -> ?T_KICK;
-            _ -> {{takeover, Action},?T_TAKEOVER}
+            _ -> ?T_TAKEOVER
         end,
     Return =
         %% this is essentailly a gen_server:call implemented in emqx_connection
         %% and emqx_ws_connection.
         %% the handle_call is implemented in emqx_channel
-        try apply(ConnMod, call, [Pid, NAction, Timeout]) of
+        try apply(ConnMod, call, [Pid, Action, Timeout]) of
             ok -> ok;
             Reply -> {ok, Reply}
         catch
@@ -332,7 +332,7 @@ takeover(Action, ConnMod, Pid) ->
                 ok = ?tp(debug, "session_already_shutdown", #{pid => Pid, action => Action}),
                 {error, Reason};
             _ : {timeout, {gen_server, call, _}} ->
-                ?tp(warning, "takeover_session_timeout",
+                ?tp(warning, "session_stepdown_request_timeout",
                     #{pid => Pid,
                       action => Action,
                       stale_channel => stale_channel_info(Pid)
@@ -340,7 +340,7 @@ takeover(Action, ConnMod, Pid) ->
                 ok = force_kill(Pid),
                 {error, timeout};
             _ : Error : St ->
-                ?tp(error, "takeover_session_exception",
+                ?tp(error, "session_stepdown_request_exception",
                     #{pid => Pid,
                       action => Action,
                       reason => Error,
@@ -375,7 +375,7 @@ kick_session(Action, ClientId, ChanPid) when node(ChanPid) == node() ->
             %% already deregistered
             ok;
         ConnMod when is_atom(ConnMod) ->
-            ok = takeover(Action, ConnMod, ChanPid)
+            ok = request_stepdown(Action, ConnMod, ChanPid)
     end;
 kick_session(Action, ClientId, ChanPid) ->
     %% call remote node on the old APIs because we do not know if they have upgraded