mirror of
https://github.com/swift-server/async-http-client.git
synced 2026-05-03 07:32:29 +00:00
Fabian Fett
fcb0f21bfd
- `ConsumerControlState` was replaced with `ResponseStreamState` in `HTTPRequestStateMachine` - `channelRead`s are buffered up to a `channelReadComplete`. - on `channelReadComplete` all buffered body parts are forwarded to the consumer
712 lines
29 KiB
Swift
712 lines
29 KiB
Swift
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the AsyncHTTPClient open source project
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//
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// Copyright (c) 2021 Apple Inc. and the AsyncHTTPClient project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of AsyncHTTPClient project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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import NIO
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import NIOHTTP1
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struct HTTPRequestStateMachine {
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fileprivate enum State {
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/// The initial state machine state. The only valid mutation is `start()`. The state will
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/// transitions to:
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/// - `.waitForChannelToBecomeWritable`
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/// - `.running(.streaming, .initialized)` (if the Channel is writable and if a request body is expected)
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/// - `.running(.endSent, .initialized)` (if the Channel is writable and no request body is expected)
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case initialized
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/// Waiting for the channel to be writable. Valid transitions are:
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/// - `.running(.streaming, .initialized)` (once the Channel is writable again and if a request body is expected)
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/// - `.running(.endSent, .initialized)` (once the Channel is writable again and no request body is expected)
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/// - `.failed` (if a connection error occurred)
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case waitForChannelToBecomeWritable(HTTPRequestHead, RequestFramingMetadata)
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/// A request is on the wire. Valid transitions are:
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/// - `.finished`
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/// - `.failed`
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case running(RequestState, ResponseState)
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/// The request has completed successfully
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case finished
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/// The request has failed
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case failed(Error)
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case modifying
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}
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/// A sub state for a running request. More specifically for sending a request body.
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fileprivate enum RequestState {
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/// A sub state for sending a request body. Stores whether a producer should produce more
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/// bytes or should pause.
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enum ProducerControlState: String {
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/// The request body producer should produce more body bytes. The channel is writable.
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case producing
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/// The request body producer should pause producing more bytes. The channel is not writable.
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case paused
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}
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/// The request is streaming its request body. `expectedBodyLength` has a value, if the request header contained
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/// a `"content-length"` header field. If the request header contained a `"transfer-encoding" = "chunked"`
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/// header field, the `expectedBodyLength` is `nil`.
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case streaming(expectedBodyLength: Int?, sentBodyBytes: Int, producer: ProducerControlState)
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/// The request has sent its request body and end.
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case endSent
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}
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fileprivate enum ResponseState {
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/// A response head has not been received yet.
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case waitingForHead
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/// A response head has been received and we are ready to consume more data off the wire
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case receivingBody(HTTPResponseHead, ResponseStreamState)
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/// A response end has been received. We don't expect more bytes from the wire.
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case endReceived
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}
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enum Action {
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/// A action to execute, when we consider a request "done".
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enum FinalStreamAction {
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/// Close the connection
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case close
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/// If the server has replied, with a status of 200...300 before all data was sent, a request is considered succeeded,
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/// as soon as we wrote the request end onto the wire.
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case sendRequestEnd
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/// Do nothing. This is action is used, if the request failed, before we the request head was written onto the wire.
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/// This might happen if the request is cancelled, or the request failed the soundness check.
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case none
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}
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case sendRequestHead(HTTPRequestHead, startBody: Bool)
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case sendBodyPart(IOData)
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case sendRequestEnd
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case pauseRequestBodyStream
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case resumeRequestBodyStream
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case forwardResponseHead(HTTPResponseHead, pauseRequestBodyStream: Bool)
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case forwardResponseBodyParts(CircularBuffer<ByteBuffer>)
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case failRequest(Error, FinalStreamAction)
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case succeedRequest(FinalStreamAction, CircularBuffer<ByteBuffer>)
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case read
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case wait
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}
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private var state: State = .initialized
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private var isChannelWritable: Bool
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init(isChannelWritable: Bool) {
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self.isChannelWritable = isChannelWritable
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}
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mutating func startRequest(head: HTTPRequestHead, metadata: RequestFramingMetadata) -> Action {
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guard case .initialized = self.state else {
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preconditionFailure("`start()` must be called first, and exactly once. Invalid state: \(self.state)")
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}
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guard self.isChannelWritable else {
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self.state = .waitForChannelToBecomeWritable(head, metadata)
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return .wait
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}
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return self.startSendingRequest(head: head, metadata: metadata)
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}
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mutating func writabilityChanged(writable: Bool) -> Action {
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if writable {
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return self.channelIsWritable()
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} else {
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return self.channelIsNotWritable()
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}
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}
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private mutating func channelIsWritable() -> Action {
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self.isChannelWritable = true
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switch self.state {
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case .initialized,
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.running(.streaming(_, _, producer: .producing), _),
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.running(.endSent, _),
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.finished,
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.failed:
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return .wait
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case .waitForChannelToBecomeWritable(let head, let metadata):
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return self.startSendingRequest(head: head, metadata: metadata)
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case .running(.streaming(_, _, producer: .paused), .receivingBody(let head, _)) where head.status.code >= 300:
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// If we are receiving a response with a status of >= 300, we should not send out
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// further request body parts. The remote already signaled with status >= 300 that it
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// won't be interested. Let's save some bandwidth.
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return .wait
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case .running(.streaming(let expectedBody, let sentBodyBytes, producer: .paused), let responseState):
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let requestState: RequestState = .streaming(
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expectedBodyLength: expectedBody,
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sentBodyBytes: sentBodyBytes,
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producer: .producing
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)
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self.state = .running(requestState, responseState)
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return .resumeRequestBodyStream
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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private mutating func channelIsNotWritable() -> Action {
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self.isChannelWritable = false
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switch self.state {
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case .initialized,
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.waitForChannelToBecomeWritable,
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.running(.streaming(_, _, producer: .paused), _),
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.running(.endSent, _),
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.finished,
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.failed:
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return .wait
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case .running(.streaming(let expectedBodyLength, let sentBodyBytes, producer: .producing), let responseState):
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let requestState: RequestState = .streaming(
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expectedBodyLength: expectedBodyLength,
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sentBodyBytes: sentBodyBytes,
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producer: .paused
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)
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self.state = .running(requestState, responseState)
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return .pauseRequestBodyStream
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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mutating func errorHappened(_ error: Error) -> Action {
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switch self.state {
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case .initialized:
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preconditionFailure("After the state machine has been initialized, start must be called immediately. Thus this state is unreachable")
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case .waitForChannelToBecomeWritable:
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// the request failed, before it was sent onto the wire.
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self.state = .failed(error)
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return .failRequest(error, .none)
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case .running:
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self.state = .failed(error)
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return .failRequest(error, .close)
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case .finished, .failed:
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preconditionFailure("If the request is finished or failed, we expect the connection state machine to remove the request immediately from its state. Thus this state is unreachable.")
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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mutating func requestStreamPartReceived(_ part: IOData) -> Action {
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switch self.state {
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case .initialized,
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.waitForChannelToBecomeWritable,
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.running(.endSent, _):
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preconditionFailure("We must be in the request streaming phase, if we receive further body parts. Invalid state: \(self.state)")
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case .running(.streaming(_, _, let producerState), .receivingBody(let head, _)) where head.status.code >= 300:
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// If we have already received a response head with status >= 300, we won't send out any
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// further request body bytes. Since the remote signaled with status >= 300, that it
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// won't be interested. We expect that the producer has been informed to pause
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// producing.
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assert(producerState == .paused)
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return .wait
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case .running(.streaming(let expectedBodyLength, var sentBodyBytes, let producerState), let responseState):
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// We don't check the producer state here:
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//
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// No matter if the `producerState` is either `.producing` or `.paused` any bytes we
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// receive shall be forwarded to the Channel right away. As long as we have not received
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// a response with status >= 300.
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//
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// More streamed data is accepted, even though the producer may have been asked to
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// pause. The reason for this is as follows: There might be thread synchronization
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// situations in which the producer might not have received the plea to pause yet.
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if let expected = expectedBodyLength, sentBodyBytes + part.readableBytes > expected {
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let error = HTTPClientError.bodyLengthMismatch
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return .failRequest(error, .close)
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}
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sentBodyBytes += part.readableBytes
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let requestState: RequestState = .streaming(
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expectedBodyLength: expectedBodyLength,
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sentBodyBytes: sentBodyBytes,
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producer: producerState
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)
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self.state = .running(requestState, responseState)
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return .sendBodyPart(part)
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case .failed:
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return .wait
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case .finished:
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// A request may be finished, before we have send all parts. This might be the case if
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// the server responded with an HTTP status code that is equal or larger to 300
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// (Redirection, Client Error or Server Error). In those cases we pause the request body
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// stream as soon as we have received the response head and we succeed the request as
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// when response end is received. This may mean, that we succeed a request, even though
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// we have not sent all it's body parts.
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// We may still receive something, here because of potential race conditions with the
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// producing thread.
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return .wait
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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mutating func requestStreamFinished() -> Action {
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switch self.state {
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case .initialized,
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.waitForChannelToBecomeWritable,
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.running(.endSent, _):
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preconditionFailure("A request body stream end is only expected if we are in state request streaming. Invalid state: \(self.state)")
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case .running(.streaming(let expectedBodyLength, let sentBodyBytes, _), .waitingForHead):
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if let expected = expectedBodyLength, expected != sentBodyBytes {
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let error = HTTPClientError.bodyLengthMismatch
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self.state = .failed(error)
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return .failRequest(error, .close)
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}
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self.state = .running(.endSent, .waitingForHead)
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return .sendRequestEnd
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case .running(.streaming(let expectedBodyLength, let sentBodyBytes, _), .receivingBody(let head, let streamState)):
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assert(head.status.code < 300)
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if let expected = expectedBodyLength, expected != sentBodyBytes {
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let error = HTTPClientError.bodyLengthMismatch
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self.state = .failed(error)
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return .failRequest(error, .close)
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}
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self.state = .running(.endSent, .receivingBody(head, streamState))
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return .sendRequestEnd
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case .running(.streaming(let expectedBodyLength, let sentBodyBytes, _), .endReceived):
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if let expected = expectedBodyLength, expected != sentBodyBytes {
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let error = HTTPClientError.bodyLengthMismatch
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self.state = .failed(error)
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return .failRequest(error, .close)
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}
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self.state = .finished
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return .succeedRequest(.sendRequestEnd, .init())
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case .failed:
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return .wait
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case .finished:
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// A request may be finished, before we have send all parts. This might be the case if
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// the server responded with an HTTP status code that is equal or larger to 300
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// (Redirection, Client Error or Server Error). In those cases we pause the request body
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// stream as soon as we have received the response head and we succeed the request as
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// when response end is received. This may mean, that we succeed a request, even though
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// we have not sent all it's body parts.
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// We may still receive something, here because of potential race conditions with the
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// producing thread.
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return .wait
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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mutating func requestCancelled() -> Action {
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switch self.state {
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case .initialized, .waitForChannelToBecomeWritable:
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let error = HTTPClientError.cancelled
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self.state = .failed(error)
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return .failRequest(error, .none)
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case .running:
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let error = HTTPClientError.cancelled
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self.state = .failed(error)
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return .failRequest(error, .close)
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case .finished:
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return .wait
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case .failed:
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return .wait
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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mutating func channelInactive() -> Action {
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switch self.state {
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case .initialized, .waitForChannelToBecomeWritable, .running:
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let error = HTTPClientError.remoteConnectionClosed
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self.state = .failed(error)
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return .failRequest(error, .none)
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case .finished:
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return .wait
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case .failed:
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// don't overwrite error
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return .wait
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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// MARK: - Response
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mutating func read() -> Action {
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switch self.state {
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case .initialized,
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.waitForChannelToBecomeWritable,
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.running(_, .waitingForHead),
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.running(_, .endReceived),
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.finished,
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.failed:
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// If we are not in the middle of streaming the response body, we always want to get
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// more data...
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return .read
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case .running(let requestState, .receivingBody(let head, var streamState)):
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// This should never happen. But we don't want to precondition this behavior. Let's just
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// pass the read event on
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return self.avoidingStateMachineCoW { (state) -> Action in
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let action = streamState.read()
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state = .running(requestState, .receivingBody(head, streamState))
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return action.toRequestAction()
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}
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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mutating func channelRead(_ part: HTTPClientResponsePart) -> Action {
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switch part {
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case .head(let head):
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return self.receivedHTTPResponseHead(head)
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case .body(let body):
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return self.receivedHTTPResponseBodyPart(body)
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case .end:
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return self.receivedHTTPResponseEnd()
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}
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}
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mutating func channelReadComplete() -> Action {
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switch self.state {
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case .initialized,
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.waitForChannelToBecomeWritable,
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.running(_, .waitingForHead),
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.running(_, .endReceived),
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.finished,
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.failed:
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return .wait
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case .running(let requestState, .receivingBody(let head, var streamState)):
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// This should never happen. But we don't want to precondition this behavior. Let's just
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// pass the read event on
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return self.avoidingStateMachineCoW { (state) -> Action in
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let buffer = streamState.channelReadComplete()
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state = .running(requestState, .receivingBody(head, streamState))
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if let buffer = buffer {
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return .forwardResponseBodyParts(buffer)
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} else {
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return .wait
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}
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}
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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private mutating func receivedHTTPResponseHead(_ head: HTTPResponseHead) -> Action {
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guard head.status.code >= 200 else {
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// we ignore any leading 1xx headers... No state change needed.
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return .wait
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}
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switch self.state {
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case .initialized, .waitForChannelToBecomeWritable:
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preconditionFailure("How can we receive a response head before sending a request head ourselves")
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case .running(.streaming(let expectedBodyLength, let sentBodyBytes, producer: .paused), .waitingForHead):
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self.state = .running(
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.streaming(expectedBodyLength: expectedBodyLength, sentBodyBytes: sentBodyBytes, producer: .paused),
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.receivingBody(head, .init())
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)
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return .forwardResponseHead(head, pauseRequestBodyStream: false)
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case .running(.streaming(let expectedBodyLength, let sentBodyBytes, producer: .producing), .waitingForHead):
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if head.status.code >= 300 {
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self.state = .running(
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.streaming(expectedBodyLength: expectedBodyLength, sentBodyBytes: sentBodyBytes, producer: .paused),
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.receivingBody(head, .init())
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)
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return .forwardResponseHead(head, pauseRequestBodyStream: true)
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} else {
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self.state = .running(
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.streaming(expectedBodyLength: expectedBodyLength, sentBodyBytes: sentBodyBytes, producer: .producing),
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.receivingBody(head, .init())
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)
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return .forwardResponseHead(head, pauseRequestBodyStream: false)
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}
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case .running(.endSent, .waitingForHead):
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self.state = .running(.endSent, .receivingBody(head, .init()))
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return .forwardResponseHead(head, pauseRequestBodyStream: false)
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case .running(_, .receivingBody), .running(_, .endReceived), .finished:
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preconditionFailure("How can we successfully finish the request, before having received a head. Invalid state: \(self.state)")
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case .failed:
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return .wait
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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mutating func receivedHTTPResponseBodyPart(_ body: ByteBuffer) -> Action {
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switch self.state {
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case .initialized, .waitForChannelToBecomeWritable:
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preconditionFailure("How can we receive a response head before sending a request head ourselves. Invalid state: \(self.state)")
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case .running(_, .waitingForHead):
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preconditionFailure("How can we receive a response body, if we haven't received a head. Invalid state: \(self.state)")
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case .running(let requestState, .receivingBody(let head, var responseStreamState)):
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return self.avoidingStateMachineCoW { (state) -> Action in
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responseStreamState.receivedBodyPart(body)
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state = .running(requestState, .receivingBody(head, responseStreamState))
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return .wait
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}
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case .running(_, .endReceived), .finished:
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preconditionFailure("How can we successfully finish the request, before having received a head. Invalid state: \(self.state)")
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case .failed:
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return .wait
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case .modifying:
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preconditionFailure("Invalid state: \(self.state)")
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}
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}
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|
|
|
private mutating func receivedHTTPResponseEnd() -> Action {
|
|
switch self.state {
|
|
case .initialized, .waitForChannelToBecomeWritable:
|
|
preconditionFailure("How can we receive a response head before sending a request head ourselves. Invalid state: \(self.state)")
|
|
|
|
case .running(_, .waitingForHead):
|
|
preconditionFailure("How can we receive a response end, if we haven't a received a head. Invalid state: \(self.state)")
|
|
|
|
case .running(.streaming(let expectedBodyLength, let sentBodyBytes, let producerState), .receivingBody(let head, var responseStreamState))
|
|
where head.status.code < 300:
|
|
|
|
return self.avoidingStateMachineCoW { state -> Action in
|
|
let remainingBuffer = responseStreamState.end()
|
|
state = .running(
|
|
.streaming(expectedBodyLength: expectedBodyLength, sentBodyBytes: sentBodyBytes, producer: producerState),
|
|
.endReceived
|
|
)
|
|
return .forwardResponseBodyParts(remainingBuffer)
|
|
}
|
|
|
|
case .running(.streaming(_, _, let producerState), .receivingBody(let head, var responseStreamState)):
|
|
assert(head.status.code >= 300)
|
|
assert(producerState == .paused, "Expected to have paused the request body stream, when the head was received. Invalid state: \(self.state)")
|
|
|
|
return self.avoidingStateMachineCoW { state -> Action in
|
|
let remainingBuffer = responseStreamState.end()
|
|
state = .finished
|
|
return .succeedRequest(.close, remainingBuffer)
|
|
}
|
|
|
|
case .running(.endSent, .receivingBody(_, var responseStreamState)):
|
|
return self.avoidingStateMachineCoW { state -> Action in
|
|
let remainingBuffer = responseStreamState.end()
|
|
state = .finished
|
|
return .succeedRequest(.none, remainingBuffer)
|
|
}
|
|
|
|
case .running(_, .endReceived), .finished:
|
|
preconditionFailure("How can we receive a response end, if another one was already received. Invalid state: \(self.state)")
|
|
|
|
case .failed:
|
|
return .wait
|
|
|
|
case .modifying:
|
|
preconditionFailure("Invalid state: \(self.state)")
|
|
}
|
|
}
|
|
|
|
mutating func demandMoreResponseBodyParts() -> Action {
|
|
switch self.state {
|
|
case .initialized,
|
|
.running(_, .waitingForHead),
|
|
.waitForChannelToBecomeWritable:
|
|
preconditionFailure("The response is expected to only ask for more data after the response head was forwarded")
|
|
|
|
case .running(let requestState, .receivingBody(let head, var responseStreamState)):
|
|
return self.avoidingStateMachineCoW { state -> Action in
|
|
let action = responseStreamState.demandMoreResponseBodyParts()
|
|
state = .running(requestState, .receivingBody(head, responseStreamState))
|
|
return action.toRequestAction()
|
|
}
|
|
|
|
case .running(_, .endReceived),
|
|
.finished,
|
|
.failed:
|
|
return .wait
|
|
|
|
case .modifying:
|
|
preconditionFailure("Invalid state: \(self.state)")
|
|
}
|
|
}
|
|
|
|
mutating func idleReadTimeoutTriggered() -> Action {
|
|
switch self.state {
|
|
case .initialized,
|
|
.waitForChannelToBecomeWritable,
|
|
.running(.streaming, _):
|
|
preconditionFailure("We only schedule idle read timeouts after we have sent the complete request. Invalid state: \(self.state)")
|
|
|
|
case .running(.endSent, .waitingForHead), .running(.endSent, .receivingBody):
|
|
let error = HTTPClientError.readTimeout
|
|
self.state = .failed(error)
|
|
return .failRequest(error, .close)
|
|
|
|
case .running(.endSent, .endReceived):
|
|
preconditionFailure("Invalid state. This state should be: .finished")
|
|
|
|
case .finished, .failed:
|
|
return .wait
|
|
|
|
case .modifying:
|
|
preconditionFailure("Invalid state: \(self.state)")
|
|
}
|
|
}
|
|
|
|
private mutating func startSendingRequest(head: HTTPRequestHead, metadata: RequestFramingMetadata) -> Action {
|
|
switch metadata.body {
|
|
case .stream:
|
|
self.state = .running(.streaming(expectedBodyLength: nil, sentBodyBytes: 0, producer: .producing), .waitingForHead)
|
|
return .sendRequestHead(head, startBody: true)
|
|
case .fixedSize(let length) where length > 0:
|
|
self.state = .running(.streaming(expectedBodyLength: length, sentBodyBytes: 0, producer: .producing), .waitingForHead)
|
|
return .sendRequestHead(head, startBody: true)
|
|
case .none, .fixedSize:
|
|
// fallback if fixed size is 0
|
|
self.state = .running(.endSent, .waitingForHead)
|
|
return .sendRequestHead(head, startBody: false)
|
|
}
|
|
}
|
|
}
|
|
|
|
extension HTTPRequestStateMachine {
|
|
/// So, uh...this function needs some explaining.
|
|
///
|
|
/// While the state machine logic above is great, there is a downside to having all of the state machine data in
|
|
/// associated data on enumerations: any modification of that data will trigger copy on write for heap-allocated
|
|
/// data. That means that for _every operation on the state machine_ we will CoW our underlying state, which is
|
|
/// not good.
|
|
///
|
|
/// The way we can avoid this is by using this helper function. It will temporarily set state to a value with no
|
|
/// associated data, before attempting the body of the function. It will also verify that the state machine never
|
|
/// remains in this bad state.
|
|
///
|
|
/// A key note here is that all callers must ensure that they return to a good state before they exit.
|
|
///
|
|
/// Sadly, because it's generic and has a closure, we need to force it to be inlined at all call sites, which is
|
|
/// not ideal.
|
|
@inline(__always)
|
|
private mutating func avoidingStateMachineCoW<ReturnType>(_ body: (inout State) -> ReturnType) -> ReturnType {
|
|
self.state = .modifying
|
|
defer {
|
|
assert(!self.isModifying)
|
|
}
|
|
|
|
return body(&self.state)
|
|
}
|
|
|
|
private var isModifying: Bool {
|
|
if case .modifying = self.state {
|
|
return true
|
|
} else {
|
|
return false
|
|
}
|
|
}
|
|
}
|
|
|
|
extension HTTPRequestStateMachine.ResponseStreamState.Action {
|
|
func toRequestAction() -> HTTPRequestStateMachine.Action {
|
|
switch self {
|
|
case .read:
|
|
return .read
|
|
case .wait:
|
|
return .wait
|
|
}
|
|
}
|
|
}
|
|
|
|
extension HTTPRequestStateMachine: CustomStringConvertible {
|
|
var description: String {
|
|
switch self.state {
|
|
case .initialized:
|
|
return "HTTPRequestStateMachine(.initialized, isWritable: \(self.isChannelWritable))"
|
|
case .waitForChannelToBecomeWritable:
|
|
return "HTTPRequestStateMachine(.waitForChannelToBecomeWritable, isWritable: \(self.isChannelWritable))"
|
|
case .running(let requestState, let responseState):
|
|
return "HTTPRequestStateMachine(.running(request: \(requestState), response: \(responseState)), isWritable: \(self.isChannelWritable))"
|
|
case .finished:
|
|
return "HTTPRequestStateMachine(.finished, isWritable: \(self.isChannelWritable))"
|
|
case .failed(let error):
|
|
return "HTTPRequestStateMachine(.failed(\(error)), isWritable: \(self.isChannelWritable))"
|
|
case .modifying:
|
|
return "HTTPRequestStateMachine(.modifying, isWritable: \(self.isChannelWritable))"
|
|
}
|
|
}
|
|
}
|
|
|
|
extension HTTPRequestStateMachine.RequestState: CustomStringConvertible {
|
|
var description: String {
|
|
switch self {
|
|
case .streaming(expectedBodyLength: let expected, let sent, producer: let producer):
|
|
return ".streaming(sent: \(expected != nil ? String(expected!) : "-"), sent: \(sent), producer: \(producer)"
|
|
case .endSent:
|
|
return ".endSent"
|
|
}
|
|
}
|
|
}
|
|
|
|
extension HTTPRequestStateMachine.ResponseState: CustomStringConvertible {
|
|
var description: String {
|
|
switch self {
|
|
case .waitingForHead:
|
|
return ".waitingForHead"
|
|
case .receivingBody(let head, let streamState):
|
|
return ".receivingBody(\(head), streamState: \(streamState))"
|
|
case .endReceived:
|
|
return ".endReceived"
|
|
}
|
|
}
|
|
}
|