refactor(ds): Move end_of_stream detection logic for delete_next

apps/emqx_durable_storage/src/emqx_ds_storage_bitfield_lts.erl

@@ -36,7 +36,7 @@
     make_delete_iterator/5,
     update_iterator/4,
     next/6,
-    delete_next/6,
+    delete_next/7,
 
     handle_event/4
 ]).
@@ -495,14 +495,19 @@ next_until(#s{db = DB, data = CF, keymappers = Keymappers}, It, SafeCutoffTime,
         rocksdb:iterator_close(ITHandle)
     end.
 
-delete_next(Shard, Schema = #s{ts_offset = TSOffset}, It, Selector, BatchSize, Now) ->
+delete_next(Shard, Schema = #s{ts_offset = TSOffset}, It, Selector, BatchSize, Now, IsCurrent) ->
     %% Compute safe cutoff time.
     %% It's the point in time where the last complete epoch ends, so we need to know
     %% the current time to compute it.
     init_counters(),
-    SafeCutoffTime = (Now bsr TSOffset) bsl TSOffset,
+    SafeCutoffTime = ?EPOCH(Schema, Now) bsl TSOffset,
     try
-        delete_next_until(Schema, It, SafeCutoffTime, Selector, BatchSize)
+        case delete_next_until(Schema, It, SafeCutoffTime, Selector, BatchSize) of
+            {ok, _It, 0, 0} when not IsCurrent ->
+                {ok, end_of_stream};
+            Result ->
+                Result
+        end
     after
         report_counters(Shard)
     end.

apps/emqx_durable_storage/src/emqx_ds_storage_layer.erl

@@ -261,6 +261,11 @@
 ) ->
     [_Stream].
 
+-callback get_delete_streams(
+    shard_id(), generation_data(), emqx_ds:topic_filter(), emqx_ds:time()
+) ->
+    [_Stream].
+
 -callback make_iterator(
     shard_id(), generation_data(), _Stream, emqx_ds:topic_filter(), emqx_ds:time()
 ) ->
@@ -282,9 +287,10 @@
     DeleteIterator,
     emqx_ds:delete_selector(),
     pos_integer(),
-    emqx_ds:time()
+    emqx_ds:time(),
+    _IsCurrentGeneration :: boolean()
 ) ->
-    {ok, DeleteIterator, _NDeleted :: non_neg_integer(), _IteratedOver :: non_neg_integer()}.
+    {ok, DeleteIterator, _NDeleted :: non_neg_integer(), _IteratedOver :: non_neg_integer()} | emqx_ds:error(_).
 
 -callback handle_event(shard_id(), generation_data(), emqx_ds:time(), CustomEvent | tick) ->
     [CustomEvent].
@@ -511,15 +517,12 @@ delete_next(
 ) ->
     case generation_get(Shard, GenId) of
         #{module := Mod, data := GenData} ->
-            Current = generation_current(Shard),
+            IsCurrent = GenId =:= generation_current(Shard),
-            case Mod:delete_next(Shard, GenData, GenIter0, Selector, BatchSize, Now) of
+            case Mod:delete_next(Shard, GenData, GenIter0, Selector, BatchSize, Now, IsCurrent) of
-                {ok, _GenIter, _Deleted = 0, _IteratedOver = 0} when GenId < Current ->
-                    %% This is a past generation. Storage layer won't write
-                    %% any more messages here. The iterator reached the end:
-                    %% the stream has been fully replayed.
-                    {ok, end_of_stream};
                 {ok, GenIter, NumDeleted, _IteratedOver} ->
                     {ok, Iter#{?enc := GenIter}, NumDeleted};
+                EOS = {ok, end_of_stream} ->
+                    EOS;
                 Error = {error, _} ->
                     Error
             end;

apps/emqx_durable_storage/src/emqx_ds_storage_reference.erl

@@ -39,7 +39,7 @@
     make_delete_iterator/5,
     update_iterator/4,
     next/6,
-    delete_next/6
+    delete_next/7
 ]).
 
 %% internal exports:
@@ -169,7 +169,7 @@ next(_Shard, #s{db = DB, cf = CF}, It0, BatchSize, _Now, IsCurrent) ->
             {ok, It, lists:reverse(Messages)}
     end.
 
-delete_next(_Shard, #s{db = DB, cf = CF}, It0, Selector, BatchSize, _Now) ->
+delete_next(_Shard, #s{db = DB, cf = CF}, It0, Selector, BatchSize, _Now, IsCurrent) ->
     #delete_it{
         topic_filter = TopicFilter,
         start_time = StartTime,
@@ -198,7 +198,12 @@ delete_next(_Shard, #s{db = DB, cf = CF}, It0, Selector, BatchSize, _Now) ->
     ),
     rocksdb:iterator_close(ITHandle),
     It = It0#delete_it{last_seen_message_key = Key},
-    {ok, It, NumDeleted, NumIterated}.
+    case IsCurrent of
+        false when NumDeleted =:= 0, NumIterated =:= 0 ->
+            {ok, end_of_stream};
+        _ ->
+            {ok, It, NumDeleted, NumIterated}
+    end.
 
 %%================================================================================
 %% Internal functions