fix: block 2.9 syncing server-side

Also allow us to disable blocking in tests

apps/arweave/include/ar_data_sync.hrl

@@ -81,6 +81,11 @@
 -define(STORE_CHUNK_QUEUE_FLUSH_TIME_THRESHOLD, 2_000). % 2 seconds.
 -endif.
 
+%% By default we prevent syncing replica 2.9 chunks since they are too expensive to unpack.
+-ifndef(BLOCK_2_9_SYNCING).
+-define(BLOCK_2_9_SYNCING, true).
+-endif.
+
 %% @doc The state of the server managing data synchronization.
 -record(sync_data_state, {
 	%% The last entries of the block index.

apps/arweave/src/ar_data_sync.erl

@@ -2810,19 +2810,13 @@ pick_missing_blocks([{H, WeaveSize, _} | CurrentBI], BlockTXPairs) ->
 		_ ->
 			{WeaveSize, lists:reverse(After)}
 	end.
-
--ifdef(AR_TEST).
-should_unpack(_) ->
-	true.
--else.
-should_unpack({replica_2_9, Addr}) ->
+should_unpack({replica_2_9, Addr}) when ?BLOCK_2_9_SYNCING ->
 	%% Unpacking another peer's replica 2.9 chunk is expensive, so don't do it.
 	%% Note: peers running the reference client won't share replica 2.9 chunks
 	%% anyways, so this check is just a backup.
 	{false, got_replica_2_9_chunk_from_peer, [{mining_addr, ar_util:encode(Addr)}]};
 should_unpack(_) ->
 	true.
--endif.
 
 process_invalid_fetched_chunk(Peer, Byte, State) ->
 	%% Not necessarily a malicious peer, it might happen

apps/arweave/src/ar_http_iface_middleware.erl

@@ -2010,11 +2010,13 @@ handle_get_chunk(OffsetBinary, Req, Encoding) ->
 							{{true, RequestedPacking}, _StoreID} ->
 								ok = ar_semaphore:acquire(get_chunk, infinity),
 								{RequestedPacking, ok};
-							{true, {replica_2_9, _}, _StoreID} ->
+							{{true, {replica_2_9, _}}, _StoreID} when ?BLOCK_2_9_SYNCING ->
 								%% Don't serve replica 2.9 chunks as they are expensive to
 								%% unpack.
 								{none, {reply, {404, #{}, <<>>, Req}}};
 							{{true, Packing}, _StoreID} when RequestedPacking == any ->
+								?LOG_INFO([{event, get_chunk3}, {requested_packing, ar_serialize:encode_packing(Packing, false)},
+									{store_id, _StoreID}, {offset, Offset}]),
 								ok = ar_semaphore:acquire(get_chunk, infinity),
 								{Packing, ok};
 							{{true, _}, _StoreID} ->