Reply pre_vote_result instead of transitioning to follower

rabbitmq · May 21, 2024 · e6bbd1a · e6bbd1a
1 parent da3d732
commit e6bbd1a
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Showing 2 changed files with 9 additions and 11 deletions.
diff --git a/src/ra_server.erl b/src/ra_server.erl
@@ -919,22 +919,19 @@ handle_candidate(#pre_vote_rpc{term = Term} = Msg,
 handle_candidate(#request_vote_rpc{}, State = #{current_term := Term}) ->
     Reply = #request_vote_result{term = Term, vote_granted = false},
     {candidate, State, [{reply, Reply}]};
-handle_candidate(#pre_vote_rpc{term = Term, last_log_index = PeerLastIdx} = Msg,
+handle_candidate(#pre_vote_rpc{term = Term, last_log_index = PeerLastIdx} = PreVote,
                  #{current_term := CurTerm,
-                   cfg := #cfg{log_id = LogId}} = State0)
+                   cfg := #cfg{log_id = LogId}} = State)
   when Term =:= CurTerm ->
-    {LastIdx, _} = last_idx_term(State0),
+    %% This clause is necessary to prevent the liveness issue reported in https://github.com/rabbitmq/ra/issues/439
+    {LastIdx, _} = last_idx_term(State),
     case PeerLastIdx > LastIdx of
         true ->
-            %% To prevent the liveness issue reported in https://github.com/rabbitmq/ra/issues/439,
-            %% if a candidate member receives a `#pre_vote_rpc{}` with a higher last index,
-            %% it should transition to the follower state.
             ?INFO("~ts: candidate pre_vote_rpc with higher last index received ~b -> ~b",
                   [LogId, LastIdx, PeerLastIdx]),
-            State = update_term_and_voted_for(Term, undefined, State0),
-            {follower, State, [{next_event, Msg}]};
+            process_pre_vote(candidate, PreVote, State);
         false ->
-            {candidate, State0, []}
+            {candidate, State, []}
     end;
 handle_candidate(#pre_vote_rpc{}, State) ->
     %% just ignore pre_votes that aren't of a higher term

diff --git a/test/ra_server_SUITE.erl b/test/ra_server_SUITE.erl
@@ -1943,8 +1943,9 @@ candidate_receives_pre_vote(_Config) ->
     {follower, #{current_term := 6}, _}
         = ra_server:handle_candidate(PreVoteRpc#pre_vote_rpc{term = 6}, State),
 
-    % candidate abdicates for higher index
-    {follower, #{}, _}
+    % candidate replies `#pre_vote_result{vote_granted=true}` for higher index
+    {candidate, #{},
+     [{reply, #pre_vote_result{token = Token, vote_granted = true}}]}
         = ra_server:handle_candidate(PreVoteRpc#pre_vote_rpc{last_log_index = 4}, State),
 
     ok.