refactor(cm): rename call_or_kill to takeover

src/emqx_cm.erl

@@ -235,13 +235,14 @@ open_session(false, ClientInfo = #{clientid := ClientId}, ConnInfo) ->
                       case takeover_session(ClientId) of
                           {ok, ConnMod, ChanPid, Session} ->
                               ok = emqx_session:resume(ClientInfo, Session),
-                              case call_or_kill({takeover, 'end'}, ConnMod, ChanPid) of
+                              case takeover('end', ConnMod, ChanPid) of
-                                  {error, _} -> CreateSess();
+                                  {ok, Pendings} ->
-                                  Pendings ->
                                       register_channel(ClientId, Self, ConnInfo),
                                       {ok, #{session  => Session,
                                              present  => true,
-                                             pendings => Pendings}}
+                                             pendings => Pendings}};
+                                  {error, _} ->
+                                      CreateSess()
                               end;
                           {error, _Reason} -> CreateSess()
                       end
@@ -277,11 +278,11 @@ takeover_session(ClientId, ChanPid) when node(ChanPid) == node() ->
         undefined ->
             {error, not_found};
         ConnMod when is_atom(ConnMod) ->
-            case call_or_kill({takeover, 'begin'}, ConnMod, ChanPid) of
+            case takeover('begin', ConnMod, ChanPid) of
+                {ok, Session} ->
+                    {ok, ConnMod, ChanPid, Session};
                 {error, Reason} ->
-                    {error, Reason};
+                    {error, Reason}
-                Session ->
-                    {ok, ConnMod, ChanPid, Session}
             end
     end;
 takeover_session(ClientId, ChanPid) ->
@@ -299,44 +300,47 @@ 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 call_or_kill(Action, module(), pid())
+-spec takeover(Action, module(), pid())
-    -> ok                        %% returned by kick, discard
+    -> ok
-     | emqx_session:session()    %% returned by {takeover, 'begin'}
+     | {ok, emqx_session:session() | list(emqx_type:deliver())}
-     | list(emqx_type:deliver()) %% returned by {takeover, 'end'}
+     | {error, term()}
-  when Action :: kick | discard | {takeover, 'begin'} | {takeover, 'end'}.
+  when Action :: kick | discard | 'begin' | 'end'.
-call_or_kill(Action, ConnMod, Pid) ->
+takeover(Action, ConnMod, Pid) ->
-    try
+    {NAction, Timeout} =
-        Timeout = case Action of
+        case Action == kick orelse Action == discard of
-                      {takeover, _} -> ?T_TAKEOVER;
+            true -> {Action, ?T_KICK};
-                      _ -> ?T_KICK
+            _ -> {{takeover, Action},?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
-        apply(ConnMod, call, [Pid, Action, Timeout])
+        try apply(ConnMod, call, [Pid, NAction, Timeout]) of
+            ok -> ok;
+            Reply -> {ok, Reply}
         catch
             _ : noproc -> % emqx_ws_connection: call
                 ok = ?tp(debug, "session_already_gone", #{pid => Pid, action => Action}),
-            return_error_if_action_is_takeover(Action, noproc);
+                {error, noproc};
             _ : {noproc, _} -> % emqx_connection: gen_server:call
                 ok = ?tp(debug, "session_already_gone", #{pid => Pid, action => Action}),
-            return_error_if_action_is_takeover(Action, noproc);
+                {error, noproc};
             _ : Reason = {shutdown, _} ->
                 ok = ?tp(debug, "session_already_shutdown", #{pid => Pid, action => Action}),
-            return_error_if_action_is_takeover(Action, Reason);
+                {error, Reason};
             _ : Reason = {{shutdown, _}, _} ->
                 ok = ?tp(debug, "session_already_shutdown", #{pid => Pid, action => Action}),
-            return_error_if_action_is_takeover(Action, Reason);
+                {error, Reason};
             _ : {timeout, {gen_server, call, _}} ->
-            ?tp(warning, "call_session_timeout",
+                ?tp(warning, "takeover_session_timeout",
                     #{pid => Pid,
                       action => Action,
                       stale_channel => stale_channel_info(Pid)
                      }),
                 ok = force_kill(Pid),
-            return_error_if_action_is_takeover(Action, timeout);
+                {error, timeout};
             _ : Error : St ->
-            ?tp(error, "call_session_exception",
+                ?tp(error, "takeover_session_exception",
                     #{pid => Pid,
                       action => Action,
                       reason => Error,
@@ -344,14 +348,13 @@ call_or_kill(Action, ConnMod, Pid) ->
                       stale_channel => stale_channel_info(Pid)
                      }),
                 ok = force_kill(Pid),
-            return_error_if_action_is_takeover(Action, Error)
+                {error, Error}
+        end,
+    case Action == kick orelse Action == discard of
+        true -> ok;
+        _ -> Return
     end.
 
-return_error_if_action_is_takeover({takeover, _}, Reason) ->
-    {error, Reason};
-return_error_if_action_is_takeover(_, _) ->
-    ok.
-
 force_kill(Pid) ->
     exit(Pid, kill),
     ok.
@@ -372,7 +375,7 @@ kick_session(Action, ClientId, ChanPid) when node(ChanPid) == node() ->
             %% already deregistered
             ok;
         ConnMod when is_atom(ConnMod) ->
-            ok = call_or_kill(Action, ConnMod, ChanPid)
+            ok = takeover(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