Class: Protocol::HTTP2::Connection

Inherits:
Object
  • Object
show all
Includes:
FlowControlled
Defined in:
lib/protocol/http2/connection.rb

Overview

This is the core connection class that handles HTTP/2 protocol semantics including stream management, settings negotiation, and frame processing.

Direct Known Subclasses

Client, Server

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from FlowControlled

#available_frame_size, #available_size, #consume_local_window, #consume_remote_window, #request_window_update, #send_window_update, #update_local_window, #window_updated

Constructor Details

#initialize(framer, local_stream_id) ⇒ Connection

Initialize a new HTTP/2 connection.



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# File 'lib/protocol/http2/connection.rb', line 23

def initialize(framer, local_stream_id)
	super()
	
	@state = :new
	
	# Hash(Integer, Stream)
	@streams = {}
	
	@framer = framer
	
	# The next stream id to use:
	@local_stream_id = local_stream_id
	
	# The biggest remote stream id seen thus far:
	@remote_stream_id = 0
	
	@local_settings = PendingSettings.new
	@remote_settings = Settings.new
	
	@decoder = HPACK::Context.new
	@encoder = HPACK::Context.new
	
	@local_window = LocalWindow.new
	@remote_window = Window.new
end

Instance Attribute Details

#dependencies ⇒ Object (readonly)

Returns the value of attribute dependencies.



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# File 'lib/protocol/http2/connection.rb', line 154

def dependencies
  @dependencies
end

#dependency ⇒ Object (readonly)

Returns the value of attribute dependency.



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# File 'lib/protocol/http2/connection.rb', line 156

def dependency
  @dependency
end

#framer ⇒ Object (readonly)

Returns the value of attribute framer.



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# File 'lib/protocol/http2/connection.rb', line 78

def framer
  @framer
end

#local_settings ⇒ Object

Current settings value for local and peer



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# File 'lib/protocol/http2/connection.rb', line 84

def local_settings
  @local_settings
end

#local_window ⇒ Object (readonly)

Our window for receiving data. When we receive data, it reduces this window. If the window gets too small, we must send a window update.



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# File 'lib/protocol/http2/connection.rb', line 89

def local_window
  @local_window
end

#remote_settings ⇒ Object

Returns the value of attribute remote_settings.



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# File 'lib/protocol/http2/connection.rb', line 85

def remote_settings
  @remote_settings
end

#remote_stream_id ⇒ Object (readonly)

The highest stream_id that has been successfully accepted by this connection.



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# File 'lib/protocol/http2/connection.rb', line 95

def remote_stream_id
  @remote_stream_id
end

#remote_window ⇒ Object (readonly)

Our window for sending data. When we send data, it reduces this window.



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# File 'lib/protocol/http2/connection.rb', line 92

def remote_window
  @remote_window
end

#state ⇒ Object

Connection state (:new, :open, :closed).



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# File 'lib/protocol/http2/connection.rb', line 81

def state
  @state
end

#streams ⇒ Object (readonly)

Returns the value of attribute streams.



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# File 'lib/protocol/http2/connection.rb', line 152

def streams
  @streams
end

Instance Method Details

#[](id) ⇒ Object

Access streams by ID, with 0 returning the connection itself.



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# File 'lib/protocol/http2/connection.rb', line 58

def [] id
	if id.zero?
		self
	else
		@streams[id]
	end
end

#accept_push_promise_stream(stream_id, &block) ⇒ Object

Accept an incoming push promise from the other side of the connection. On the client side, we accept push promise streams. On the server side, existing streams create push promise streams.



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# File 'lib/protocol/http2/connection.rb', line 420

def accept_push_promise_stream(stream_id, &block)
	accept_stream(stream_id, &block)
end

#accept_stream(stream_id, &block) ⇒ Object

Accept an incoming stream from the other side of the connnection. On the server side, we accept requests.



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# File 'lib/protocol/http2/connection.rb', line 409

def accept_stream(stream_id, &block)
	unless valid_remote_stream_id?(stream_id)
		raise ProtocolError, "Invalid stream id: #{stream_id}"
	end
	
	create_stream(stream_id, &block)
end

#client_stream_id?(id) ⇒ Boolean

Check if the given stream ID represents a client-initiated stream. Client streams always have odd numbered IDs.

Returns:

  • (Boolean) 


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# File 'lib/protocol/http2/connection.rb', line 501

def client_stream_id?(id)
	id.odd?
end

#close(error = nil) ⇒ Object

Close the underlying framer and all streams.



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# File 'lib/protocol/http2/connection.rb', line 110

def close(error = nil)
	# The underlying socket may already be closed by this point.
	
	# If there are active streams when the connection closes, it's an error for those streams, even if the connection itself closed cleanly:
	if @streams.any? and error.nil?
		error = EOFError.new("Connection closed with #{@streams.size} active stream(s)!")
	end
	
	@streams.each_value{|stream| stream.close(error)}
	@streams.clear
	
ensure
	if @framer
		@framer.close
		@framer = nil
	end
end

#close! ⇒ Object

Transition the connection into the closed state.



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# File 'lib/protocol/http2/connection.rb', line 215

def close!
	@state = :closed
	
	return self
end

#closed? ⇒ Boolean

Whether the connection is effectively or actually closed.

Returns:

  • (Boolean) 


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# File 'lib/protocol/http2/connection.rb', line 98

def closed?
	@state == :closed || @framer.nil?
end

#closed_stream_id?(id) ⇒ Boolean

This is only valid if the stream doesn't exist in @streams.

Returns:

  • (Boolean) 


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# File 'lib/protocol/http2/connection.rb', line 535

def closed_stream_id?(id)
	if id.zero?
		# The connection "stream id" can never be closed:
		false
	else
		!idle_stream_id?(id)
	end
end

#consume_window(size = self.available_size) ⇒ Object

Traverse active streams and allow them to consume the available flow-control window.



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# File 'lib/protocol/http2/connection.rb', line 561

def consume_window(size = self.available_size)
	# Return if there is no window to consume:
	return unless size > 0
	
	@streams.each_value do |stream|
		if stream.active?
			stream.window_updated(size)
		end
	end
end

#create_push_promise_stream(&block) ⇒ Object

Create a push promise stream. This method should be overridden by client/server implementations.



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# File 'lib/protocol/http2/connection.rb', line 443

def create_push_promise_stream(&block)
	create_stream(&block)
end

#create_stream(id = next_stream_id, &block) ⇒ Stream

Create a stream, defaults to an outgoing stream. On the client side, we create requests.

Returns:

  • (Stream) —

    the created stream.



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# File 'lib/protocol/http2/connection.rb', line 427

def create_stream(id = next_stream_id, &block)
	if @streams.key?(id)
		raise ProtocolError, "Cannot create stream with id #{id}, already exists!"
	end
	
	if block_given?
		return yield(self, id)
	else
		return Stream.create(self, id)
	end
end

#decode_headers(data) ⇒ Object

Decode headers using HPACK decompression.



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# File 'lib/protocol/http2/connection.rb', line 139

def decode_headers(data)
	HPACK::Decompressor.new(data, @decoder, table_size_limit: @local_settings.header_table_size).decode
end

#delete(id) ⇒ Object

Remove a stream from the active streams collection.



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# File 'lib/protocol/http2/connection.rb', line 105

def delete(id)
	@streams.delete(id)
end

#encode_headers(headers, buffer = String.new.b) ⇒ Object

Encode headers using HPACK compression.



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# File 'lib/protocol/http2/connection.rb', line 132

def encode_headers(headers, buffer = String.new.b)
	HPACK::Compressor.new(buffer, @encoder, table_size_limit: @remote_settings.header_table_size).encode(headers)
end

#id ⇒ Object

The connection stream ID (always 0 for connection-level operations).



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# File 'lib/protocol/http2/connection.rb', line 51

def id
	0
end

#idle_stream_id?(id) ⇒ Boolean

Check if the given stream ID represents an idle stream.

Returns:

  • (Boolean) 


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# File 'lib/protocol/http2/connection.rb', line 516

def idle_stream_id?(id)
	if id.even?
		# Server-initiated streams are even.
		if @local_stream_id.even?
			id >= @local_stream_id
		else
			id > @remote_stream_id
		end
	elsif id.odd?
		# Client-initiated streams are odd.
		if @local_stream_id.odd?
			id >= @local_stream_id
		else
			id > @remote_stream_id
		end
	end
end

#ignore_frame?(frame) ⇒ Boolean

6.8. GOAWAY There is an inherent race condition between an endpoint starting new streams and the remote sending a GOAWAY frame. To deal with this case, the GOAWAY contains the stream identifier of the last peer-initiated stream that was or might be processed on the sending endpoint in this connection. For instance, if the server sends a GOAWAY frame, the identified stream is the highest-numbered stream initiated by the client. Once sent, the sender will ignore frames sent on streams initiated by the receiver if the stream has an identifier higher than the included last stream identifier. Receivers of a GOAWAY frame MUST NOT open additional streams on the connection, although a new connection can be established for new streams.

Returns:

  • (Boolean) 


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# File 'lib/protocol/http2/connection.rb', line 161

def ignore_frame?(frame)
	if self.closed?
		# puts "ignore_frame? #{frame.stream_id} -> #{valid_remote_stream_id?(frame.stream_id)} > #{@remote_stream_id}"
		if valid_remote_stream_id?(frame.stream_id)
			return frame.stream_id > @remote_stream_id
		end
	end
end

#maximum_concurrent_streams ⇒ Object

The maximum number of concurrent streams that this connection can initiate. This is a setting that can be changed by the remote peer.

It is not the same as the number of streams that can be accepted by the connection. The number of streams that can be accepted is determined by the local settings, and the number of streams that can be initiated is determined by the remote settings.



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# File 'lib/protocol/http2/connection.rb', line 74

def maximum_concurrent_streams
	@remote_settings.maximum_concurrent_streams
end

#maximum_frame_size ⇒ Object

The size of a frame payload is limited by the maximum size that a receiver advertises in the SETTINGS_MAX_FRAME_SIZE setting.



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# File 'lib/protocol/http2/connection.rb', line 67

def maximum_frame_size
	@remote_settings.maximum_frame_size
end

#next_stream_id ⇒ Object

Streams are identified with an unsigned 31-bit integer. Streams initiated by a client MUST use odd-numbered stream identifiers; those initiated by the server MUST use even-numbered stream identifiers. A stream identifier of zero (0x0) is used for connection control messages; the stream identifier of zero cannot be used to establish a new stream.



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# File 'lib/protocol/http2/connection.rb', line 144

def next_stream_id
	id = @local_stream_id
	
	@local_stream_id += 2
	
	return id
end

#open! ⇒ Object

Transition the connection to the open state.



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# File 'lib/protocol/http2/connection.rb', line 331

def open!
	@state = :open
	
	return self
end

#process_settings(frame) ⇒ Boolean

In addition to changing the flow-control window for streams that are not yet active, a SETTINGS frame can alter the initial flow-control window size for streams with active flow-control windows (that is, streams in the "open" or "half-closed (remote)" state). When the value of SETTINGS_INITIAL_WINDOW_SIZE changes, a receiver MUST adjust the size of all stream flow-control windows that it maintains by the difference between the new value and the old value.

Returns:

  • (Boolean) —

    whether the frame was an acknowledgement



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# File 'lib/protocol/http2/connection.rb', line 306

def process_settings(frame)
	if frame.acknowledgement?
		# The remote end has confirmed the settings have been received:
		changes = @local_settings.acknowledge
		
		update_local_settings(changes)
		
		return true
	else
		# The remote end is updating the settings, we reply with acknowledgement:
		reply = frame.acknowledge
		
		write_frame(reply)
		
		changes = frame.unpack
		@remote_settings.update(changes)
		
		update_remote_settings(changes)
		
		return false
	end
end

#read_frame ⇒ Object

Reads one frame from the network and processes. Processing the frame updates the state of the connection and related streams. If the frame triggers an error, e.g. a protocol error, the connection will typically emit a goaway frame and re-raise the exception. You should continue processing frames until the underlying connection is closed.



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# File 'lib/protocol/http2/connection.rb', line 178

def read_frame
	frame = @framer.read_frame(@local_settings.maximum_frame_size)
	
	# puts "#{self.class} #{@state} read_frame: class=#{frame.class} stream_id=#{frame.stream_id} flags=#{frame.flags} length=#{frame.length} (remote_stream_id=#{@remote_stream_id})"
	# puts "Windows: local_window=#{@local_window.inspect}; remote_window=#{@remote_window.inspect}"
	
	return if ignore_frame?(frame)
	
	yield frame if block_given?
	frame.apply(self)
	
	return frame
rescue GoawayError => error
	# Go directly to jail. Do not pass go, do not collect $200.
	raise
rescue ProtocolError => error
	send_goaway(error.code || PROTOCOL_ERROR, error.message)
	
	raise
rescue HPACK::Error => error
	send_goaway(COMPRESSION_ERROR, error.message)
	
	raise
end

#receive_continuation(frame) ⇒ Object

Receive and process a CONTINUATION frame.

Raises:



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# File 'lib/protocol/http2/connection.rb', line 596

def receive_continuation(frame)
	raise ProtocolError, "Received unexpected continuation: #{frame.class}"
end

#receive_data(frame) ⇒ Object

Process a DATA frame from the remote peer.



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# File 'lib/protocol/http2/connection.rb', line 387

def receive_data(frame)
	update_local_window(frame)
	
	if stream = @streams[frame.stream_id]
		stream.receive_data(frame)
	elsif closed_stream_id?(frame.stream_id)
		# This can occur if one end sent a stream reset, while the other end was sending a data frame. It's mostly harmless.
	else
		raise ProtocolError, "Cannot receive data for stream id #{frame.stream_id}"
	end
end

#receive_frame(frame) ⇒ Object

Receive and process a generic frame (default handler).



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# File 'lib/protocol/http2/connection.rb', line 602

def receive_frame(frame)
	# ignore.
end

#receive_goaway(frame) ⇒ Object

Process a GOAWAY frame from the remote peer.



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# File 'lib/protocol/http2/connection.rb', line 234

def receive_goaway(frame)
	# We capture the last stream that was processed.
	@remote_stream_id, error_code, message = frame.unpack
	
	self.close!
	
	# Streams above the last stream ID were not processed by the remote peer and are safe to retry (RFC 9113 ยง6.8).
	error = ::Protocol::HTTP::RefusedError.new("GOAWAY: request not processed.")
	
	@streams.each_value do |stream|
		if stream.id > @remote_stream_id
			stream.close(error)
		end
	end
	
	if error_code != 0
		# Shut down immediately.
		raise GoawayError.new(message, error_code)
	end
end

#receive_headers(frame) ⇒ Object

On the server side, starts a new request.



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# File 'lib/protocol/http2/connection.rb', line 448

def receive_headers(frame)
	stream_id = frame.stream_id
	
	if stream_id.zero?
		raise ProtocolError, "Cannot receive headers for stream 0!"
	end
	
	if stream = @streams[stream_id]
		stream.receive_headers(frame)
	else
		if stream_id <= @remote_stream_id
			raise ProtocolError, "Invalid stream id: #{stream_id} <= #{@remote_stream_id}!"
		end
		
		# We need to validate that we have less streams than the specified maximum:
		if @streams.size < @local_settings.maximum_concurrent_streams
			stream = accept_stream(stream_id)
			@remote_stream_id = stream_id
			
			stream.receive_headers(frame)
		else
			raise ProtocolError, "Exceeded maximum concurrent streams"
		end
	end
end

#receive_ping(frame) ⇒ Object

Process a PING frame from the remote peer.



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# File 'lib/protocol/http2/connection.rb', line 367

def receive_ping(frame)
	if @state != :closed
		# This is handled in `read_payload`:
		# if frame.stream_id != 0
		# 	raise ProtocolError, "Ping received for non-zero stream!"
		# end
		
		unless frame.acknowledgement?
			reply = frame.acknowledge
			
			write_frame(reply)
		end
	else
		raise ProtocolError, "Cannot receive ping in state #{@state}"
	end
end

#receive_priority_update(frame) ⇒ Object

Receive and process a PRIORITY_UPDATE frame.



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# File 'lib/protocol/http2/connection.rb', line 484

def receive_priority_update(frame)
	if frame.stream_id != 0
		raise ProtocolError, "Invalid stream id: #{frame.stream_id}"
	end
	
	stream_id, value = frame.unpack
	
	# Apparently you can set the priority of idle streams, but I'm not sure why that makes sense, so for now let's ignore it.
	if stream = @streams[stream_id]
		stream.priority = Protocol::HTTP::Header::Priority.new(value)
	end
end

#receive_push_promise(frame) ⇒ Object

Receive and process a PUSH_PROMISE frame.

Raises:



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# File 'lib/protocol/http2/connection.rb', line 477

def receive_push_promise(frame)
	raise ProtocolError, "Unable to receive push promise!"
end

#receive_reset_stream(frame) ⇒ Object

Receive and process a RST_STREAM frame.



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# File 'lib/protocol/http2/connection.rb', line 547

def receive_reset_stream(frame)
	if frame.connection?
		raise ProtocolError, "Cannot reset connection!"
	elsif stream = @streams[frame.stream_id]
		stream.receive_reset_stream(frame)
	elsif closed_stream_id?(frame.stream_id)
		# Ignore.
	else
		raise StreamClosed, "Cannot reset stream #{frame.stream_id}"
	end
end

#receive_settings(frame) ⇒ Object

Receive and process a SETTINGS frame from the remote peer.



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# File 'lib/protocol/http2/connection.rb', line 340

def receive_settings(frame)
	if @state == :new
		# We transition to :open when we receive acknowledgement of first settings frame:
		open! if process_settings(frame)
	elsif @state != :closed
		process_settings(frame)
	else
		raise ProtocolError, "Cannot receive settings in state #{@state}"
	end
end

#receive_window_update(frame) ⇒ Object

Receive and process a WINDOW_UPDATE frame.



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# File 'lib/protocol/http2/connection.rb', line 574

def receive_window_update(frame)
	if frame.connection?
		super
		
		self.consume_window
	elsif stream = @streams[frame.stream_id]
		begin
			stream.receive_window_update(frame)
		rescue ProtocolError => error
			stream.send_reset_stream(error.code)
		end
	elsif closed_stream_id?(frame.stream_id)
		# Ignore.
	else
		# Receiving any frame other than HEADERS or PRIORITY on a stream in this state (idle) MUST be treated as a connection error of type PROTOCOL_ERROR.
		raise ProtocolError, "Cannot update window of idle stream #{frame.stream_id}"
	end
end

#send_goaway(error_code = 0, message = "") ⇒ Object

Tell the remote end that the connection is being shut down. If the error_code is 0, this is a graceful shutdown. The other end of the connection should not make any new streams, but existing streams may be completed.



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# File 'lib/protocol/http2/connection.rb', line 222

def send_goaway(error_code = 0, message = "")
	frame = GoawayFrame.new
	frame.pack @remote_stream_id, error_code, message
	
	write_frame(frame)
ensure
	self.close!
end

#send_ping(data) ⇒ Object

Send a PING frame to the remote peer.



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# File 'lib/protocol/http2/connection.rb', line 353

def send_ping(data)
	if @state != :closed
		frame = PingFrame.new
		frame.pack data
		
		write_frame(frame)
	else
		raise ProtocolError, "Cannot send ping in state #{@state}"
	end
end

#send_settings(changes) ⇒ Object

Send updated settings to the remote peer.



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# File 'lib/protocol/http2/connection.rb', line 205

def send_settings(changes)
	@local_settings.append(changes)
	
	frame = SettingsFrame.new
	frame.pack(changes)
	
	write_frame(frame)
end

#server_stream_id?(id) ⇒ Boolean

Check if the given stream ID represents a server-initiated stream. Server streams always have even numbered IDs.

Returns:

  • (Boolean) 


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# File 'lib/protocol/http2/connection.rb', line 509

def server_stream_id?(id)
	id.even?
end

#synchronize ⇒ Object

Execute a block within a synchronized context. This method provides a synchronization primitive for thread safety.



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# File 'lib/protocol/http2/connection.rb', line 173

def synchronize
	yield
end

#update_local_settings(changes) ⇒ Object

Update local settings and adjust stream window capacities.



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# File 'lib/protocol/http2/connection.rb', line 283

def update_local_settings(changes)
	capacity = @local_settings.initial_window_size
	
	@streams.each_value do |stream|
		stream.local_window.capacity = capacity
	end
	
	@local_window.desired = capacity
end

#update_remote_settings(changes) ⇒ Object

Update remote settings and adjust stream window capacities.



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# File 'lib/protocol/http2/connection.rb', line 295

def update_remote_settings(changes)
	capacity = @remote_settings.initial_window_size
	
	@streams.each_value do |stream|
		stream.remote_window.capacity = capacity
	end
end

#valid_remote_stream_id?(stream_id) ⇒ Boolean

Check if the given stream ID is valid for remote initiation. This method should be overridden by client/server implementations.

Returns:

  • (Boolean) 


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# File 'lib/protocol/http2/connection.rb', line 403

def valid_remote_stream_id?(stream_id)
	false
end

#write_frame(frame) ⇒ Object

Write a single frame to the connection.



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# File 'lib/protocol/http2/connection.rb', line 257

def write_frame(frame)
	synchronize do
		@framer.write_frame(frame)
	end
	
	@framer.flush
end

#write_frames ⇒ Object

Write multiple frames within a synchronized block.



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# File 'lib/protocol/http2/connection.rb', line 269

def write_frames
	if @framer
		synchronize do
			yield @framer
		end
		
		@framer.flush
	else
		raise EOFError, "Connection closed!"
	end
end