module HTTP2Next::FlowBuffer
Implementation of stream and connection DATA flow control: frames may be split and / or may be buffered based on current flow control window.
Constants
- MAX_WINDOW_SIZE
Public Instance Methods
buffered_amount()
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Amount of buffered data. Only DATA payloads are subject to flow stream and connection flow control.
@return [Integer]
# File lib/http/2/next/flow_buffer.rb, line 16 def buffered_amount send_buffer.bytesize end
flush()
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# File lib/http/2/next/flow_buffer.rb, line 20 def flush send_data end
Private Instance Methods
calculate_window_update(window_max_size)
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# File lib/http/2/next/flow_buffer.rb, line 36 def calculate_window_update(window_max_size) # If DATA frame is received with length > 0 and # current received window size + delta length is strictly larger than # local window size, it throws a flow control error. # error(:flow_control_error) if @local_window < 0 # Send WINDOW_UPDATE if the received window size goes over # the local window size / 2. # # The HTTP/2 spec mandates that every DATA frame received # generates a WINDOW_UPDATE to send. In some cases however, # (ex: DATA frames with short payloads), # the noise generated by flow control frames creates enough # congestion for this to be deemed very inefficient. # # This heuristic was inherited from nghttp, which delays the # WINDOW_UPDATE until at least half the window is exhausted. # This works because the sender doesn't need those increments # until the receiver window is exhausted, after which he'll be # waiting for the WINDOW_UPDATE frame. return unless @local_window <= (window_max_size / 2) window_update(window_max_size - @local_window) end
process_window_update(frame:, encode: false)
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# File lib/http/2/next/flow_buffer.rb, line 90 def process_window_update(frame:, encode: false) return if frame[:ignore] if frame[:increment] raise ProtocolError, "increment MUST be higher than zero" if frame[:increment].zero? @remote_window += frame[:increment] error(:flow_control_error, msg: "window size too large") if @remote_window > MAX_WINDOW_SIZE end send_data(nil, encode) end
send_buffer()
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# File lib/http/2/next/flow_buffer.rb, line 26 def send_buffer @send_buffer ||= FrameBuffer.new end
send_data(frame = nil, encode = false)
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Buffers outgoing DATA frames and applies flow control logic to split and emit DATA frames based on current flow control window. If the window is large enough, the data is sent immediately. Otherwise, the data is buffered until the flow control window is updated.
Buffered DATA frames are emitted in FIFO order.
@param frame [Hash] @param encode [Boolean] set to true by connection
# File lib/http/2/next/flow_buffer.rb, line 71 def send_data(frame = nil, encode = false) send_buffer << frame unless frame.nil? while (frame = send_buffer.retrieve(@remote_window)) # puts "#{self.class} -> #{@remote_window}" sent = frame[:payload].bytesize manage_state(frame) do if encode encode(frame).each { |f| emit(:frame, f) } else emit(:frame, frame) end @remote_window -= sent end end end
update_local_window(frame)
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# File lib/http/2/next/flow_buffer.rb, line 30 def update_local_window(frame) frame_size = frame[:payload].bytesize frame_size += frame[:padding] || 0 @local_window -= frame_size end