extract code into new module

follower ignores pre_vote and request_vote

src/ra.hrl

@@ -20,8 +20,6 @@
 -type ra_index() :: non_neg_integer().
 %% Section 5.3.
 -type ra_term() :: non_neg_integer().
-%% Section 4.2.1
--type ra_replication_round() :: non_neg_integer().
 
 %% tuple form of index and term
 -type ra_idxterm() :: {ra_index(), ra_term()}.
@@ -46,20 +44,12 @@
                           suspended |
                           disconnected.
 
-%% A peer can be one of:
-%%
-%% - Voter, standard quorum member.
-%% - Nonvoter, node does not participate in elections or consensus voting.
-%% - Staging, node is a temporary nonvoter, and will be automatically promoted
-%%            if it proves to be fast enough to stay up to dat with teh leader.
--type ra_voter() :: yes | no | {maybe, staging_status()}.
-
-%% For staging nodes we measure current round, target index and the timestamp of its start.
-%% If the node reaches target index and the ∂T is less than the election timeout, the node is
-%% considered eligible to become a voter.
--type staging_status() :: #{round  := ra_replication_round(),
-                            target := ra_index(),
-                            ts     := integer()}.
+-type ra_voter() :: yes | {no, ra_nonvoter_status()}.
+
+-type ra_nonvoter_status() :: permanent |
+                              #{round  := non_neg_integer(),
+                                target := ra_index(),
+                                ts     := integer()}.
 
 -type ra_peer_state() :: #{next_index := non_neg_integer(),
                            match_index := non_neg_integer(),

src/ra_server.erl

@@ -85,6 +85,7 @@
       query_index := non_neg_integer(),
       queries_waiting_heartbeats := queue:queue({non_neg_integer(), consistent_query_ref()}),
       pending_consistent_queries := [consistent_query_ref()],
+      voter => 'maybe'(ra_voter()),
       commit_latency => 'maybe'(non_neg_integer())
      }.
 
@@ -1105,8 +1106,14 @@ handle_follower({ra_log_event, Evt}, State = #{log := Log0}) ->
     % simply forward all other events to ra_log
     {Log, Effects} = ra_log:handle_event(Evt, Log0),
     {follower, State#{log => Log}, Effects};
+handle_follower(#pre_vote_rpc{}, #{voter := {no, _}} = State) ->
+    %% ignore elections, non-voter
+    {follower, State, []};
 handle_follower(#pre_vote_rpc{} = PreVote, State) ->
     process_pre_vote(follower, PreVote, State);
+handle_follower(#request_vote_rpc{}, #{voter := {no, _}} = State) ->
+    %% ignore elections, non-voter
+    {follower, State, []};
 handle_follower(#request_vote_rpc{candidate_id = Cand, term = Term},
                 #{current_term := Term, voted_for := VotedFor,
                   cfg := #cfg{log_id = LogId}} = State)
@@ -1204,6 +1211,9 @@ handle_follower(#append_entries_reply{}, State) ->
     %% handle to avoid logging as unhandled
     %% could receive a lot of these shortly after standing down as leader
     {follower, State, []};
+handle_follower(election_timeout, #{voter := {no, _}} = State) ->
+    %% ignore elections, non-voter
+    {follower, State, []};
 handle_follower(election_timeout, State) ->
     call_for_election(pre_vote, State);
 handle_follower(try_become_leader, State) ->
@@ -2095,10 +2105,6 @@ new_peer() ->
 new_peer_with(Map) ->
     maps:merge(new_peer(), Map).
 
-new_staging_status(State) ->
-    TargetIdx = maps:get(commit_index, State),
-    #{round => 0, target => TargetIdx , ts => os:system_time(millisecond)}.
-
 already_member(State) ->
     % already a member do nothing
     % TODO: reply? If we don't reply the caller may block until timeout
@@ -2330,6 +2336,7 @@ apply_with({Idx, Term, {'$ra_cluster_change', CmdMeta, NewCluster, ReplyType}},
                            [log_id(State0), maps:keys(NewCluster)]),
                     %% we are recovering and should apply the cluster change
                     State0#{cluster => NewCluster,
+                            voter => ra_voter:peer_status(id(State0), NewCluster),
                             cluster_change_permitted => true,
                             cluster_index_term => {Idx, Term}};
                 _  ->
@@ -2468,7 +2475,7 @@ append_log_leader({'$ra_join', From, JoiningNode, ReplyMode},
     case OldCluster of
         #{JoiningNode := #{voter := yes}} ->
             already_member(State);
-        #{JoiningNode := #{voter := {maybe, _}} = Peer} ->
+        #{JoiningNode := #{voter := {no, _}} = Peer} ->
             Cluster = OldCluster#{JoiningNode => Peer#{voter => yes}},
             append_cluster_change(Cluster, From, ReplyMode, State);
         _ ->
@@ -2481,8 +2488,7 @@ append_log_leader({'$ra_maybe_join', From, JoiningNode, ReplyMode},
         #{JoiningNode := _} ->
             already_member(State);
         _ ->
-            Round0 = new_staging_status(State),
-            Cluster = OldCluster#{JoiningNode => new_peer_with(#{voter => {maybe, Round0}})},
+            Cluster = OldCluster#{JoiningNode => new_peer_with(#{voter =>  ra_voter:new_nonvoter(State)})},
             append_cluster_change(Cluster, From, ReplyMode, State)
     end;
 append_log_leader({'$ra_leave', From, LeavingServer, ReplyMode},
@@ -2514,6 +2520,7 @@ pre_append_log_follower({Idx, Term, Cmd} = Entry,
     case Cmd of
         {'$ra_cluster_change', _, Cluster, _} ->
             State#{cluster => Cluster,
+                   voter => ra_voter:peer_status(id(State), Cluster),
                    cluster_index_term => {Idx, Term}};
         _ ->
             % revert back to previous cluster
@@ -2525,6 +2532,7 @@ pre_append_log_follower({Idx, Term, Cmd} = Entry,
 pre_append_log_follower({Idx, Term, {'$ra_cluster_change', _, Cluster, _}},
                         State) ->
     State#{cluster => Cluster,
+           voter => ra_voter:peer_status(id(State), Cluster),
            cluster_index_term => {Idx, Term}};
 pre_append_log_follower(_, State) ->
     State.

src/ra_voter.erl

@@ -0,0 +1,28 @@
+%% This Source Code Form is subject to the terms of the Mozilla Public
+%%
+%% Copyright (c) 2017-2022 VMware, Inc. or its affiliates.  All rights reserved.
+%%
+-module(ra_voter).
+
+-export([
+         new_nonvoter/1,
+         status/1,
+         peer_status/2
+        ]).
+
+new_nonvoter(State) ->
+    TargetIdx = maps:get(commit_index, State),
+    {no, #{round => 0, target => TargetIdx , ts => os:system_time(millisecond)}}.
+
+status(State) ->
+    case maps:get(voter, State) of
+        undefined ->
+            MyId = ra_server:id(State),
+            #{cluster := Cluster} = State,
+            peer_status(MyId, Cluster);
+        Voter -> Voter
+    end.
+
+peer_status(PeerId, Cluster) ->
+    Peer = maps:get(PeerId, Cluster, undefined),
+    maps:get(voter, Peer, yes).

test/ra_server_SUITE.erl

@@ -41,7 +41,6 @@ all() ->
      follower_machine_version,
      follower_install_snapshot_machine_version,
      leader_server_join,
-     leader_server_maybe_join,
      leader_server_leave,
      leader_is_removed,
      follower_cluster_change,
@@ -1334,47 +1333,6 @@ leader_server_join(_Config) ->
      | _] = Effects,
     ok.
 
-leader_server_maybe_join(_Config) ->
-    N1 = ?N1, N2 = ?N2, N3 = ?N3, N4 = ?N4,
-    OldCluster = #{N1 => new_peer_with(#{next_index => 4, match_index => 3}),
-                   N2 => new_peer_with(#{next_index => 4, match_index => 3}),
-                   N3 => new_peer_with(#{next_index => 4, match_index => 3})},
-    State0 = (base_state(3, ?FUNCTION_NAME))#{cluster => OldCluster},
-    Round0 = new_staging_status(State0),
-    % raft servers should switch to the new configuration after log append
-    % and further cluster changes should be disallowed
-    {leader, #{cluster := #{N1 := _, N2 := _, N3 := _, N4 := _},
-               cluster_change_permitted := false} = _State1, Effects} =
-        ra_server:handle_leader({command, {'$ra_maybe_join', meta(),
-                                           N4, await_consensus}}, State0),
-    [
-     {send_rpc, N4,
-      #append_entries_rpc{entries =
-                          [_, _, _, {4, 5, {'$ra_cluster_change', _,
-                                            #{N1 := _, N2 := _,
-                                              N3 := _, N4 := #{voter := {maybe, Round0}}},
-                                            await_consensus}}]}},
-     {send_rpc, N3,
-      #append_entries_rpc{entries =
-                          [{4, 5, {'$ra_cluster_change', _,
-                                   #{N1 := _, N2 := _, N3 := _, N4 := #{voter := {maybe, Round0}}},
-                                   await_consensus}}],
-                          term = 5, leader_id = N1,
-                          prev_log_index = 3,
-                          prev_log_term = 5,
-                          leader_commit = 3}},
-     {send_rpc, N2,
-      #append_entries_rpc{entries =
-                          [{4, 5, {'$ra_cluster_change', _,
-                                   #{N1 := _, N2 := _, N3 := _, N4 := #{voter := {maybe, Round0}}},
-                                   await_consensus}}],
-                          term = 5, leader_id = N1,
-                          prev_log_index = 3,
-                          prev_log_term = 5,
-                          leader_commit = 3}}
-     | _] = Effects,
-    ok.
-
 leader_server_leave(_Config) ->
     N1 = ?N1, N2 = ?N2, N3 = ?N3, N4 = ?N4,
     OldCluster = #{N1 => new_peer_with(#{next_index => 4, match_index => 3}),
@@ -2641,10 +2599,6 @@ new_peer() ->
 new_peer_with(Map) ->
     maps:merge(new_peer(), Map).
 
-new_staging_status(State) ->
-    TargetIdx = maps:get(commit_index, State),
-    #{round => 0, target => TargetIdx , ts => os:system_time(millisecond)}.
-
 snap_meta(Idx, Term) ->
     snap_meta(Idx, Term, []).