fix: avoid uploading blocks too frequently and splitting large buffers

Fixes emqx#13069 (comment)

apps/emqx_bridge_azure_blob_storage/src/emqx_bridge_azure_blob_storage_action_schema.erl

@@ -144,6 +144,16 @@ fields(aggregation) ->
                     default => 1_000_000,
                     desc => ?DESC("aggregation_max_records")
                 }
+            )},
+        {min_block_size,
+            mk(
+                emqx_schema:bytesize(),
+                #{
+                    default => <<"10mb">>,
+                    importance => ?IMPORTANCE_HIDDEN,
+                    required => true,
+                    validator => fun block_size_validator/1
+                }
             )}
     ];
 fields(common_action_parameters) ->
@@ -156,7 +166,7 @@ fields(common_action_parameters) ->
                     importance => ?IMPORTANCE_HIDDEN,
                     desc => ?DESC("max_block_size"),
                     required => true,
-                    validator => fun max_block_size_validator/1
+                    validator => fun block_size_validator/1
                 }
             )}
     ];
@@ -293,7 +303,7 @@ scunion(Field, Schemas, {value, Value}) ->
             throw(#{field_name => Field, expected => maps:keys(Schemas)})
     end.
 
-max_block_size_validator(SizeLimit) ->
+block_size_validator(SizeLimit) ->
     case SizeLimit =< 4_000 * 1024 * 1024 of
         true -> ok;
         false -> {error, "must be less than 4000 MiB"}

apps/emqx_bridge_azure_blob_storage/src/emqx_bridge_azure_blob_storage_connector.erl

@@ -55,10 +55,6 @@
 %% `emqx_template' API
 -export([lookup/2]).
 
--ifdef(TEST).
--export([take_chunk/2]).
--endif.
-
 %%------------------------------------------------------------------------------
 %% Type declarations
 %%------------------------------------------------------------------------------
@@ -131,6 +127,7 @@
         action := binary(),
         blob := emqx_template:t(),
         container := string(),
+        min_block_size := pos_integer(),
         max_block_size := pos_integer(),
         pool := connector_resource_id()
     }
@@ -144,6 +141,8 @@
     buffer_size := non_neg_integer(),
     container := container(),
     max_block_size := pos_integer(),
+    min_block_size := pos_integer(),
+    next_block := queue:queue(iolist()),
     num_blocks := non_neg_integer(),
     pool := pool_name(),
     started := boolean()
@@ -348,6 +347,7 @@ init_transfer_state(Buffer, Opts) ->
             blob := BlobTemplate,
             container := Container,
             max_block_size := MaxBlockSize,
+            min_block_size := MinBlockSize,
             pool := Pool
         }
     } = Opts,
@@ -358,6 +358,8 @@ init_transfer_state(Buffer, Opts) ->
         buffer_size => 0,
         container => Container,
         max_block_size => MaxBlockSize,
+        min_block_size => MinBlockSize,
+        next_block => queue:new(),
         num_blocks => 0,
         pool => Pool,
         started => false
@@ -371,12 +373,25 @@ mk_blob_name_key(Buffer, ActionName, BlobTemplate) ->
 process_append(IOData, TransferState0) ->
     #{
         buffer := Buffer,
-        buffer_size := BufferSize0
+        buffer_size := BufferSize0,
+        min_block_size := MinBlockSize,
+        next_block := NextBlock0
     } = TransferState0,
-    TransferState0#{
-        buffer := [Buffer, IOData],
-        buffer_size := BufferSize0 + iolist_size(IOData)
-    }.
+    Size = iolist_size(IOData),
+    case Size + BufferSize0 >= MinBlockSize of
+        true ->
+            %% Block is ready to be written.
+            TransferState0#{
+                buffer := [],
+                buffer_size := 0,
+                next_block := queue:in([Buffer, IOData], NextBlock0)
+            };
+        false ->
+            TransferState0#{
+                buffer := [Buffer, IOData],
+                buffer_size := BufferSize0 + Size
+            }
+    end.
 
 -spec process_write(transfer_state()) ->
     {ok, transfer_state()} | {error, term()}.
@@ -396,25 +411,19 @@ process_write(TransferState0 = #{started := false}) ->
         {error, Reason} ->
             {error, Reason}
     end;
-process_write(TransferState = #{started := true, buffer_size := 0}) ->
-    {ok, TransferState};
 process_write(TransferState0 = #{started := true}) ->
     #{
-        buffer := Buffer,
-        buffer_size := BufferSize,
-        max_block_size := MaxBlockSize
+        next_block := NextBlock0
     } = TransferState0,
-    case BufferSize > MaxBlockSize of
-        true ->
-            {IOData, NewBuffer} = take_chunk(Buffer, MaxBlockSize),
+    case queue:out(NextBlock0) of
+        {{value, Block}, NextBlock} ->
             ?tp(azure_blob_storage_will_write_chunk, #{}),
-            do_process_write(IOData, NewBuffer, TransferState0);
-        false ->
-            NewBuffer = [],
-            do_process_write(Buffer, NewBuffer, TransferState0)
+            do_process_write(Block, TransferState0#{next_block := NextBlock});
+        {empty, _} ->
+            {ok, TransferState0}
     end.
 
-do_process_write(IOData, NewBuffer, TransferState0 = #{started := true}) ->
+do_process_write(IOData, TransferState0 = #{started := true}) ->
     #{
         blob := Blob,
         container := Container,
@@ -423,12 +432,7 @@ do_process_write(IOData, NewBuffer, TransferState0 = #{started := true}) ->
     } = TransferState0,
     case append_data(Pool, Container, Blob, block_id(NumBlocks), IOData) of
         {ok, _} ->
-            BufferSize = iolist_size(NewBuffer),
-            TransferState = TransferState0#{
-                buffer := NewBuffer,
-                buffer_size := BufferSize,
-                num_blocks := NumBlocks + 1
-            },
+            TransferState = TransferState0#{num_blocks := NumBlocks + 1},
             process_write(TransferState);
         {error, Reason} ->
             {error, Reason}
@@ -439,10 +443,21 @@ do_process_write(IOData, NewBuffer, TransferState0 = #{started := true}) ->
 process_complete(TransferState) ->
     #{
         blob := Blob,
+        buffer := Buffer,
+        buffer_size := BufferSize,
         container := Container,
-        num_blocks := NumBlocks,
+        num_blocks := NumBlocks0,
         pool := Pool
     } = TransferState,
+    %% Flush any left-over data
+    NumBlocks =
+        case BufferSize > 0 of
+            true ->
+                {ok, #{num_blocks := NumBlocks1}} = do_process_write(Buffer, TransferState),
+                NumBlocks1;
+            false ->
+                NumBlocks0
+        end,
     BlockRefs = [{block_id(N), latest} || N <- lists:seq(0, NumBlocks - 1)],
     case put_block_list(Pool, Container, Blob, BlockRefs) of
         {ok, _} ->
@@ -511,6 +526,7 @@ install_action(#{parameters := #{mode := aggregated}} = ActionConfig, ConnState)
             aggregation := #{
                 container := ContainerOpts,
                 max_records := MaxRecords,
+                min_block_size := MinBlockSize,
                 time_interval := TimeInterval
             },
             container := ContainerName,
@@ -531,6 +547,7 @@ install_action(#{parameters := #{mode := aggregated}} = ActionConfig, ConnState)
         blob => Blob,
         container => ContainerName,
         max_block_size => MaxBlockSize,
+        min_block_size => MinBlockSize,
         pool => Pool
     },
     DeliveryOpts = #{
@@ -707,49 +724,6 @@ check_aggreg_upload_errors(AggregId) ->
 check_container_accessible(Pool, Container) ->
     list_blobs(Pool, Container).
 
--spec take_chunk(transfer_buffer(), pos_integer()) -> {_IOList :: iolist(), transfer_buffer()}.
-take_chunk(Buffer, MaxBlockSize) ->
-    RemainingBytes = MaxBlockSize,
-    take_chunk(Buffer, RemainingBytes, _IOListAcc = []).
-
--spec take_chunk(transfer_buffer(), non_neg_integer(), IOList) ->
-    {IOList, transfer_buffer()}
-when
-    IOList :: iolist().
-take_chunk(RemainingBuffer = [], _RemainingBytes, IOListAcc) ->
-    {IOListAcc, RemainingBuffer};
-take_chunk(RemainingBuffer, RemainingBytes, IOListAcc) when RemainingBytes =< 0 ->
-    {IOListAcc, [RemainingBuffer]};
-take_chunk([Data0], RemainingBytes, IOListAcc) ->
-    case do_take_chunk([Data0], RemainingBytes) of
-        {done, Data} ->
-            {[IOListAcc, Data], _RemainingBuffer = []};
-        {more, {Data, Rest}} ->
-            {[IOListAcc, Data], [Rest]}
-    end;
-take_chunk([Data0, Rest0], RemainingBytes0, IOListAcc) ->
-    case do_take_chunk(Data0, RemainingBytes0) of
-        {done, Data} ->
-            RemainingBytes = RemainingBytes0 - iolist_size(Data),
-            take_chunk([Rest0], RemainingBytes, [IOListAcc, Data]);
-        {more, {Data, Rest}} ->
-            {[IOListAcc, Data], [Rest, Rest0]}
-    end.
-
-do_take_chunk(Data, ChunkSize) ->
-    case iolist_size(Data) =< ChunkSize of
-        true ->
-            {done, Data};
-        false ->
-            BinData0 = iolist_to_binary(Data),
-            {more, split_binary(BinData0, ChunkSize)}
-    end.
-
-%% ensure_transfer_buffer_shape([_, _] = Buffer) ->
-%%     Buffer;
-%% ensure_transfer_buffer_shape(Data) ->
-%%     [Data].
-
 block_id(N) ->
     NumDigits = 32,
     list_to_binary(string:pad(integer_to_list(N), NumDigits, leading, $0)).

apps/emqx_bridge_azure_blob_storage/test/emqx_bridge_azure_blob_storage_SUITE.erl

@@ -615,7 +615,9 @@ t_aggreg_pending_upload_restart(Config) ->
                     #{
                         <<"parameters">> =>
                             #{
-                                <<"max_block_size">> => <<"1024B">>
+                                <<"aggregation">> => #{
+                                    <<"min_block_size">> => <<"1024B">>
+                                }
                             }
                     }
                 )