handle missing segments event after follower recovery

Author: kjnilsson

src/ra_server.erl

@@ -405,6 +405,7 @@ init(#{id := Id,
                              maps:get(membership, Config, voter)),
 
     #{cfg => Cfg,
+      leader_id => undefined,
       current_term => CurrentTerm,
       cluster => Cluster0,
       % There may be scenarios when a single server
@@ -1340,8 +1341,8 @@ handle_follower(#heartbeat_rpc{leader_id = LeaderId,
     {follower, State, [cast_reply(Id, LeaderId, Reply)]};
 handle_follower({ra_log_event, Evt}, #{log := Log0,
                                        cfg := #cfg{id = Id},
-                                       leader_id := LeaderId,
                                        current_term := Term} = State0) ->
+    LeaderId = maps:get(leader_id, State0, undefined),
     % forward events to ra_log
     % if the last written changes then send an append entries reply
     LW = ra_log:last_written(Log0),

test/ra_log_2_SUITE.erl

@@ -1832,9 +1832,10 @@ sparse_write(Config) ->
     SnapState0 = ra_log:snapshot_state(Log2),
     {ok, SnapState1} = ra_snapshot:begin_accept(Meta, SnapState0),
     Machine = {machine, ?MODULE, #{}},
-    {SnapState, _, LiveIndexes, AEffs} = ra_snapshot:complete_accept(Chunk, 1,
-                                                                     Machine,
-                                                                     SnapState1),
+    {SnapState, _, LiveIndexesSeq, AEffs} = ra_snapshot:complete_accept(Chunk, 1,
+                                                                        Machine,
+                                                                        SnapState1),
+    ?assertEqual(LiveIndexes, lists:reverse(ra_seq:expand(LiveIndexesSeq))),
     run_effs(AEffs),
     Log3 = ra_log:set_snapshot_state(SnapState, Log2),
     {ok, Log4, _} = ra_log:install_snapshot({15, 2}, ?MODULE,