Remove pending entries after snapshot installation.

Else we may end up with pending entries that never will
be written and will later trigger a resend that will fail.

Author: kjnilsson

src/ra_log.erl

@@ -1141,6 +1141,7 @@ install_snapshot({SnapIdx, SnapTerm} = IdxTerm, MacMod, LiveIndexes,
                  #?MODULE{cfg = #cfg{uid = UId,
                                      names = Names} = Cfg,
                           snapshot_state = SnapState0,
+                          pending = Pend0,
                           mem_table = Mt0} = State0)
   when is_atom(MacMod) ->
     ok = incr_counter(Cfg, ?C_RA_LOG_SNAPSHOTS_INSTALLED, 1),
@@ -1160,9 +1161,10 @@ install_snapshot({SnapIdx, SnapTerm} = IdxTerm, MacMod, LiveIndexes,
                                 I
                         end,
     %% TODO: more mt entries could potentially be cleared up in the
-    %% mem table here
+    %% mem table here if we walked the live indexes
     {Spec, Mt1} = ra_mt:set_first(SmallestLiveIndex, Mt0),
     ok = exec_mem_table_delete(Names, UId, Spec),
+    Pend = ra_seq:floor(SmallestLiveIndex, Pend0),
     %% always create a new mem table here as we could have written
     %% sparese entries in the snapshot install
     %% TODO: check an empty mt doesn't leak
@@ -1174,6 +1176,7 @@ install_snapshot({SnapIdx, SnapTerm} = IdxTerm, MacMod, LiveIndexes,
                            last_term = SnapTerm,
                            live_indexes = LiveIndexes,
                            mem_table = Mt,
+                           pending = Pend,
                            last_written_index_term = IdxTerm},
     {Reader, CompEffs} = ra_log_segments:schedule_compaction(minor, SnapIdx,
                                                              LiveIndexes,

test/ra_log_2_SUITE.erl

@@ -58,6 +58,7 @@ all_tests() ->
      wal_loses_writer_state,
      detect_lost_written_range,
      snapshot_installation,
+     snapshot_installation_with_no_live_indexes_overtakes_written,
      snapshot_written_after_installation,
      oldcheckpoints_deleted_after_snapshot_install,
      append_after_snapshot_installation_with_live_indexes,
@@ -177,7 +178,6 @@ snapshot_before_written(Config) ->
                       end),
     ok.
 
-
 handle_overwrite(Config) ->
     Log0 = ra_log_init(Config),
     {ok, Log1} = ra_log:write([{1, 1, "value"},
@@ -1625,6 +1625,38 @@ snapshot_installation(Config) ->
     {[_, _], _} = ra_log_take(16, 17, Log),
     ok.
 
+snapshot_installation_with_no_live_indexes_overtakes_written(Config) ->
+    Log0 = ra_log_init(Config),
+    {0, 0} = ra_log:last_index_term(Log0),
+    Log1 = assert_log_events(write_n(1, 10, 2, Log0),
+                             fun (L) -> {9, 2} == ra_log:last_written(L) end),
+
+    true = ra_log_wal_SUITE:suspend_process(whereis(ra_log_wal)),
+    Log2 = write_n(1, 10, 2, Log1),
+
+    %% create snapshot chunk
+    Meta = meta(15, 2, [?N1]),
+    Chunk = create_snapshot_chunk(Config, Meta, #{}),
+    SnapState0 = ra_log:snapshot_state(Log2),
+    {ok, SnapState1} = ra_snapshot:begin_accept(Meta, SnapState0),
+    Machine = {machine, ?MODULE, #{}},
+    {SnapState, _, [], AEffs} =
+        ra_snapshot:complete_accept(Chunk, 1, Machine, SnapState1),
+    run_effs(AEffs),
+    {ok, Log3, Effs4} = ra_log:install_snapshot({15, 2}, ?MODULE, [],
+                                                ra_log:set_snapshot_state(SnapState, Log2)),
+
+    run_effs(Effs4),
+    {15, _} = ra_log:last_index_term(Log3),
+    {15, _} = ra_log:last_written(Log3),
+    #{mem_table_range := undefined} = ra_log:overview(Log3),
+
+    true = erlang:resume_process(whereis(ra_log_wal)),
+    Log4 = write_n(16, 20, 2, Log3),
+    _ = assert_log_events(Log4,
+                             fun (L) -> {19, 2} == ra_log:last_written(L) end),
+    ok.
+
 append_after_snapshot_installation_with_live_indexes(Config) ->
     logger:set_primary_config(level, all),
     %% simulates scenario where a node becomes leader after receiving a