stream snapshot when reading from file

src/cli/blockchain_cli_snapshot.erl

@@ -213,7 +213,7 @@ snapshot_list(["snapshot", "list"], [], []) ->
     Chain = blockchain_worker:blockchain(),
     Snapshots = blockchain:find_last_snapshots(Chain, 5),
     case Snapshots of
-        undefined -> ok;
+        undefined -> [clique_status:text("No snapshot found")];
         _ ->
             [ clique_status:text(io_lib:format("Height ~p\nHash ~p (~p)\nHave ~p\n",
                                                [Height, Hash, binary_to_hex(Hash),

src/handlers/blockchain_snapshot_handler.erl

@@ -8,6 +8,7 @@
 -behavior(libp2p_framed_stream).
 
 
+-include_lib("kernel/include/file.hrl").
 -include_lib("helium_proto/include/blockchain_snapshot_handler_pb.hrl").
 
 %% ------------------------------------------------------------------
@@ -101,9 +102,8 @@ handle_data(server, Data, #state{chain = Chain} = State) ->
         #blockchain_snapshot_req_pb{height = _Height, hash = Hash} ->
             case blockchain:get_snapshot(Hash, Chain) of
                 {ok, {file, FileName}} ->
-                    {ok, Bin} = file:read_file(FileName),
-                    Msg = #blockchain_snapshot_resp_pb{snapshot = Bin},
-                    {noreply, State, blockchain_snapshot_handler_pb:encode_msg(Msg)};
+                    lager:info("streaming snapshot from ~p", [FileName]),
+                    {noreply, State, mk_file_stream_fun(FileName)};
                 {ok, Snap} ->
                     lager:info("sending snapshot ~p", [Hash]),
                     Msg = #blockchain_snapshot_resp_pb{snapshot = Snap},
@@ -121,3 +121,40 @@ handle_data(server, Data, #state{chain = Chain} = State) ->
 handle_info(_Type, _Msg, State) ->
     lager:info("unhandled message ~p ~p", [_Type, _Msg]),
     {noreply, State}.
+
+%% ------------------------------------------------------------------
+%% internal functions
+%% ------------------------------------------------------------------
+
+% convert integer to varint encoding for protocol buffer
+varint(I, Bin) when I =< 127 -> <<Bin/binary, I>>;
+varint(I, Bin) -> varint(I bsr 7, <<Bin/binary, (I band 127 bor 128)>>).
+
+
+-define(FILE_STREAM_BLOCKSIZE, 4096).
+
+% send file bytes in chunks
+mk_file_stream_fun(File) when is_pid(File)->
+    case file:read(File, ?FILE_STREAM_BLOCKSIZE) of
+        {ok, Data} ->
+            fun() ->
+                    {mk_file_stream_fun(File), Data}
+            end;
+        eof ->
+            file:close(File),
+            fun() -> ok end
+    end;
+mk_file_stream_fun(FileName) ->
+    {ok, #file_info{size = Bytes}} = file:read_file_info(FileName),
+    {ok, File} = file:open(FileName, [read, binary]),
+    PBSize = varint(Bytes, <<>>),
+    %% 18 introduces a protocol buffers bytes type
+    Msg0 = <<18, PBSize/binary>>,
+    HdrSize = byte_size(Msg0),
+    {ok, Data} = file:read(File, ?FILE_STREAM_BLOCKSIZE - HdrSize),
+    Msg = <<Msg0/binary, Data/binary>>,
+    {Bytes + HdrSize,
+      fun() ->
+                {mk_file_stream_fun(File), Msg}
+      end
+    }.