ra_log:set_last_index/2 fix

Author: kjnilsson

src/ra_log.erl

@@ -751,7 +751,13 @@ set_last_index(Idx, #?MODULE{cfg = Cfg,
                                last_written_index_term = Cur}};
         {Term, State1} ->
             LWIdx = min(Idx, LWIdx0),
-            {LWTerm, State2} = fetch_term(LWIdx, State1),
+            {LWTerm, State2} = case Cur of
+                                   {LWIdx, SnapTerm} ->
+                                       {SnapTerm, State1};
+                                   _ ->
+                                       fetch_term(LWIdx, State1)
+                               end,
+
             %% this should always be found but still assert just in case
             %% _if_ this ends up as a genuine reversal next time we try
             %% to write to the mem table it will detect this and open

src/ra_server.erl

@@ -610,12 +610,12 @@ handle_leader({command, Cmd}, #{cfg := #cfg{id = Self,
             State = State0#{condition =>
                             #{predicate_fun => fun wal_down_condition/2,
                               transition_to => leader,
-                              %% TODO: make duration configurable?
                               timeout => #{duration => 5000,
                                            effects => CondEffs,
                                            transition_to => leader}}},
 
-            {await_condition, State, Effects0};
+            Effects = append_error_reply(Cmd, wal_down, Effects0),
+            {await_condition, State, Effects};
         {not_appended, Reason, State, Effects0} ->
             ?WARN("~ts command ~W NOT appended to log. Reason ~w",
                   [LogId, Cmd, 10, Reason]),

test/ra_log_2_SUITE.erl

@@ -1445,9 +1445,12 @@ snapshot_installation(Config) ->
     % after a snapshot we need a "truncating write" that ignores missing
     % indexes
     Log5 = write_n(16, 20, 2, Log4),
-    {[], _} = ra_log_take(1, 9, Log5),
-    {[_, _], _} = ra_log_take(16, 17, Log5),
-    Log6 = assert_log_events(Log5, fun (L) ->
+    %% check that the log can be reset to a pending write index
+    {ok, Log5b} = ra_log:set_last_index(19, Log5),
+
+    {[], _} = ra_log_take(1, 9, Log5b),
+    {[_, _], _} = ra_log_take(16, 17, Log5b),
+    Log6 = assert_log_events(Log5b, fun (L) ->
                                            {19, 2} == ra_log:last_written(L)
                                    end),
     {[], _} = ra_log_take(1, 9, Log6),