diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/cow_http2_machine.erl | 90 |
1 files changed, 89 insertions, 1 deletions
diff --git a/src/cow_http2_machine.erl b/src/cow_http2_machine.erl index 4c30da3..0cf99fb 100644 --- a/src/cow_http2_machine.erl +++ b/src/cow_http2_machine.erl @@ -24,6 +24,8 @@ -export([prepare_push_promise/4]). -export([prepare_trailers/3]). -export([send_or_queue_data/4]). +-export([ensure_window/2]). +-export([ensure_window/3]). -export([update_window/2]). -export([update_window/3]). -export([reset_stream/2]). @@ -33,16 +35,22 @@ -export([get_stream_remote_state/2]). -type opts() :: #{ + connection_window_margin_size => 0..16#7fffffff, + connection_window_update_threshold => 0..16#7fffffff, enable_connect_protocol => boolean(), initial_connection_window_size => 65535..16#7fffffff, initial_stream_window_size => 0..16#7fffffff, + max_connection_window_size => 0..16#7fffffff, max_concurrent_streams => non_neg_integer() | infinity, max_decode_table_size => non_neg_integer(), max_encode_table_size => non_neg_integer(), max_frame_size_received => 16384..16777215, max_frame_size_sent => 16384..16777215 | infinity, + max_stream_window_size => 0..16#7fffffff, preface_timeout => timeout(), - settings_timeout => timeout() + settings_timeout => timeout(), + stream_window_margin_size => 0..16#7fffffff, + stream_window_update_threshold => 0..16#7fffffff }. -export_type([opts/0]). @@ -1279,6 +1287,86 @@ queue_data(Stream=#stream{local_buffer=Q0, local_buffer_size=Size0}, IsFin, Data Stream#stream{local_buffer=Q, local_buffer_size=Size0 + DataSize}. %% Public interface to update the flow control window. +%% +%% The ensure_window function applies heuristics to avoid updating the +%% window when it is not necessary. The update_window function updates +%% the window unconditionally. +%% +%% The ensure_window function should be called when requesting more +%% data (for example when reading a request or response body) as well +%% as when receiving new data. Failure to do so may result in the +%% window being depleted. +%% +%% The heuristics dictating whether the window must be updated and +%% what the window size is depends on three options (margin, max +%% and threshold) along with the Size argument. The window increment +%% returned by this function may therefore be smaller than the Size +%% argument. On the other hand the total window allocated over many +%% calls may end up being larger than the initial Size argument. As +%% a result, it is the responsibility of the caller to ensure that +%% the Size argument is never lower than 0. + +ensure_window(Size, State=#http2_machine{opts=Opts, remote_window=RemoteWindow}) -> + case ensure_window(Size, RemoteWindow, connection, Opts) of + ok -> + ok; + {ok, Increment} -> + {ok, Increment, State#http2_machine{remote_window=RemoteWindow + Increment}} + end. + +ensure_window(StreamID, Size, State=#http2_machine{opts=Opts}) -> + Stream = #stream{remote_window=RemoteWindow} = stream_get(StreamID, State), + case ensure_window(Size, RemoteWindow, stream, Opts) of + ok -> + ok; + {ok, Increment} -> + {ok, Increment, stream_store(Stream#stream{remote_window=RemoteWindow + Increment}, State)} + end. + +%% No need to update the window when we are not expecting data. +ensure_window(0, _, _, _) -> + ok; +%% No need to update the window when it is already high enough. +ensure_window(Size, Window, _, _) when Size =< Window -> + ok; +ensure_window(Size0, Window, Type, Opts) -> + Threshold = ensure_window_threshold(Type, Opts), + if + %% We do not update the window when it is higher than the threshold. + Window > Threshold -> + ok; + true -> + Margin = ensure_window_margin(Type, Opts), + Size = Size0 + Margin, + MaxWindow = ensure_window_max(Type, Opts), + Increment = if + %% We cannot go above the maximum window size. + Size > MaxWindow -> MaxWindow - Window; + true -> Size - Window + end, + case Increment of + 0 -> ok; + _ -> {ok, Increment} + end + end. + +%% Margin defaults to the default initial window size. +ensure_window_margin(connection, Opts) -> + maps:get(connection_window_margin_size, Opts, 65535); +ensure_window_margin(stream, Opts) -> + maps:get(stream_window_margin_size, Opts, 65535). + +%% Max window defaults to the max value allowed by the protocol. +ensure_window_max(connection, Opts) -> + maps:get(max_connection_window_size, Opts, 16#7fffffff); +ensure_window_max(stream, Opts) -> + maps:get(max_stream_window_size, Opts, 16#7fffffff). + +%% Threshold defaults to 10 times the default frame size. +ensure_window_threshold(connection, Opts) -> + maps:get(connection_window_update_threshold, Opts, 163840); +ensure_window_threshold(stream, Opts) -> + maps:get(stream_window_update_threshold, Opts, 163840). -spec update_window(1..16#7fffffff, State) -> State when State::http2_machine(). |