我目前正在使用 SwiftNIO 和 SwiftNIOHTTP2 测试版在 Swift 中开发一个简单的 HTTP2 客户端。 我的实现如下所示:
let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
let bootstrap = ClientBootstrap(group: group)
.channelOption(ChannelOptions.socket(SocketOptionLevel(SOL_SOCKET), SO_REUSEADDR), value: 1)
.channelInitializer { channel in
channel.pipeline.add(handler: HTTP2Parser(mode: .client)).then {
let multiplexer = HTTP2StreamMultiplexer { (channel, streamID) -> EventLoopFuture<Void> in
return channel.pipeline.add(handler: HTTP2ToHTTP1ClientCodec(streamID: streamID, httpProtocol: .https))
}
return channel.pipeline.add(handler: multiplexer)
}
}
defer {
try! group.syncShutdownGracefully()
}
let url = URL(string: "https://strnmn.me")!
_ = try bootstrap.connect(host: url.host!, port: url.port ?? 443)
.wait()
不幸的是，连接总是因错误而失败:
nghttp2 error: Remote peer returned unexpected data while we expected SETTINGS frame. Perhaps, peer does not support HTTP/2 properly.
但是，从命令行使用 nghttp2 连接和发出一个简单的请求工作正常。
$ nghttp -vn https://strnmn.me
[ 0.048] Connected
The negotiated protocol: h2
[ 0.110] recv SETTINGS frame <length=18, flags=0x00, stream_id=0>
(niv=3)
[SETTINGS_MAX_CONCURRENT_STREAMS(0x03):128]
[SETTINGS_INITIAL_WINDOW_SIZE(0x04):65536]
[SETTINGS_MAX_FRAME_SIZE(0x05):16777215]
[ 0.110] recv WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0>
(window_size_increment=2147418112)
[ 0.110] send SETTINGS frame <length=12, flags=0x00, stream_id=0>
(niv=2)
[SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100]
[SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535]
[ 0.110] send SETTINGS frame <length=0, flags=0x01, stream_id=0>
; ACK
(niv=0)
[ 0.110] send PRIORITY frame <length=5, flags=0x00, stream_id=3>
(dep_stream_id=0, weight=201, exclusive=0)
[ 0.110] send PRIORITY frame <length=5, flags=0x00, stream_id=5>
(dep_stream_id=0, weight=101, exclusive=0)
[ 0.110] send PRIORITY frame <length=5, flags=0x00, stream_id=7>
(dep_stream_id=0, weight=1, exclusive=0)
[ 0.110] send PRIORITY frame <length=5, flags=0x00, stream_id=9>
(dep_stream_id=7, weight=1, exclusive=0)
[ 0.110] send PRIORITY frame <length=5, flags=0x00, stream_id=11>
(dep_stream_id=3, weight=1, exclusive=0)
[ 0.111] send HEADERS frame <length=35, flags=0x25, stream_id=13>
; END_STREAM | END_HEADERS | PRIORITY
(padlen=0, dep_stream_id=11, weight=16, exclusive=0)
; Open new stream
:method: GET
:path: /
:scheme: https
:authority: strnmn.me
accept: */*
accept-encoding: gzip, deflate
user-agent: nghttp2/1.34.0
[ 0.141] recv SETTINGS frame <length=0, flags=0x01, stream_id=0>
; ACK
(niv=0)
[ 0.141] recv (stream_id=13) :status: 200
[ 0.141] recv (stream_id=13) server: nginx
[ 0.141] recv (stream_id=13) date: Sat, 24 Nov 2018 16:29:13 GMT
[ 0.141] recv (stream_id=13) content-type: text/html
[ 0.141] recv (stream_id=13) last-modified: Sat, 01 Jul 2017 20:23:11 GMT
[ 0.141] recv (stream_id=13) vary: Accept-Encoding
[ 0.141] recv (stream_id=13) etag: W/"595804af-8a"
[ 0.141] recv (stream_id=13) expires: Sat, 24 Nov 2018 16:39:13 GMT
[ 0.141] recv (stream_id=13) cache-control: max-age=600
[ 0.141] recv (stream_id=13) x-frame-options: SAMEORIGIN
[ 0.141] recv (stream_id=13) content-encoding: gzip
[ 0.141] recv HEADERS frame <length=185, flags=0x04, stream_id=13>
; END_HEADERS
(padlen=0)
; First response header
[ 0.142] recv DATA frame <length=114, flags=0x01, stream_id=13>
; END_STREAM
[ 0.142] send GOAWAY frame <length=8, flags=0x00, stream_id=0>
(last_stream_id=0, error_code=NO_ERROR(0x00), opaque_data(0)=[])
如何使用 SwiftNIOHTTP2 建立 session 并发出 GET 请求？
最佳答案
这是个很好的问题!我们先分析一下为什么这比发送 HTTP/1.x 请求要复杂。从广义上讲，这些问题分为两类:
- NIO 目前使它变得比必要的更复杂，因此我接下来要写的很多内容有时可能不直观。我是 NIO 核心团队的一员，我什至不得不挖掘相当多的代码才能使其完全正常工作，主要是因为我们仍然没有
swift-nio-ssl的文档生成。和swift-nio-http2在 http://docs.swiftnio.io . - HTTP/2 只是比 HTTP/1 复杂得多，而 NIO 更像是一个可用于构建 HTTP 客户端的工具箱，因此我们需要结合使用大量工具才能使其全部正常工作。
我将在这里重点介绍必要的复杂性 (2)，并将提交 (1) 的错误/修复。让我们检查一下我们需要 NIO 工具箱中的哪些工具来实现这一点:
- TLS。没有任何真实世界的 HTTP/2 服务器会允许您通过明文传输 HTTP/2
- ALPN。 HTTP/1 和 HTTP/2 共享同一个端口(通常是
443)，所以我们需要告诉服务器我们想要使用 HTTP/2，因为为了向后兼容，默认仍然是 HTTP/1。我们可以使用一种称为 ALPN (Application-layer Protocol Negotiation) 的机制来做到这一点，另一种选择是将 HTTP/1 升级到 HTTP2，但这更复杂且性能更差，所以我们不要在这里这样做 - 一些 HTTP/2 工具:a) 打开一个新的 HTTP/2 b) HTTP/2 到 HTTP/1 的消息转换 c) HTTP/2 多路复用
您问题中的代码包含最重要的位，即上面列表中的 3b 和 3c。但是我们需要添加 1、2 和 3a，所以让我们这样做:)
让我们从 2) ALPN 开始:
let tlsConfig = TLSConfiguration.forClient(applicationProtocols: ["h2"])
let sslContext = try SSLContext(configuration: tlsConfig)
这是一个带有 "h2" ALPN 协议(protocol)标识符的 SSL 配置，它将告诉服务器我们想要使用 HTTP/2，如 HTTP/2 spec 中所述。 .
好的，让我们使用之前设置的 sslContext 添加 TLS:
let sslHandler = try! OpenSSLClientHandler(context: sslContext, serverHostname: hostname)
同样重要的是，我们告诉 OpenSSLClientHandler 服务器的主机名，以便它可以正确验证证书。
最后我们需要做 3a(创建一个新的 HTTP/2 流来发出我们的请求)，这可以使用 ChannelHandler 轻松完成:
/// Creates a new HTTP/2 stream when our channel is active and adds the `SendAGETRequestHandler` so a request is sent.
final class CreateRequestStreamHandler: ChannelInboundHandler {
typealias InboundIn = Never
private let multiplexer: HTTP2StreamMultiplexer
private let responseReceivedPromise: EventLoopPromise<[HTTPClientResponsePart]>
init(multiplexer: HTTP2StreamMultiplexer, responseReceivedPromise: EventLoopPromise<[HTTPClientResponsePart]>) {
self.multiplexer = multiplexer
self.responseReceivedPromise = responseReceivedPromise
}
func channelActive(ctx: ChannelHandlerContext) {
func requestStreamInitializer(channel: Channel, streamID: HTTP2StreamID) -> EventLoopFuture<Void> {
return channel.pipeline.addHandlers([HTTP2ToHTTP1ClientCodec(streamID: streamID, httpProtocol: .https),
SendAGETRequestHandler(responseReceivedPromise: self.responseReceivedPromise)],
first: false)
}
// this is the most important line: When the channel is active we add the `HTTP2ToHTTP1ClientCodec` to deal in HTTP/1 messages as well as the `SendAGETRequestHandler` which will send a request.
self.multiplexer.createStreamChannel(promise: nil, requestStreamInitializer)
}
}
好的，脚手架就完成了。 SendAGETRequestHandler 是最后一部分，它是一个处理程序，一旦我们之前打开的新 HTTP/2 流成功打开，就会添加该处理程序。为了查看完整的响应，我还实现了将响应的所有位累加到一个 promise 中:
/// Fires off a GET request when our stream is active and collects all response parts into a promise.
///
/// - warning: This will read the whole response into memory and delivers it into a promise.
final class SendAGETRequestHandler: ChannelInboundHandler {
typealias InboundIn = HTTPClientResponsePart
typealias OutboundOut = HTTPClientRequestPart
private let responseReceivedPromise: EventLoopPromise<[HTTPClientResponsePart]>
private var responsePartAccumulator: [HTTPClientResponsePart] = []
init(responseReceivedPromise: EventLoopPromise<[HTTPClientResponsePart]>) {
self.responseReceivedPromise = responseReceivedPromise
}
func channelActive(ctx: ChannelHandlerContext) {
assert(ctx.channel.parent!.isActive)
var reqHead = HTTPRequestHead(version: .init(major: 2, minor: 0), method: .GET, uri: "/")
reqHead.headers.add(name: "Host", value: hostname)
ctx.write(self.wrapOutboundOut(.head(reqHead)), promise: nil)
ctx.writeAndFlush(self.wrapOutboundOut(.end(nil)), promise: nil)
}
func channelRead(ctx: ChannelHandlerContext, data: NIOAny) {
let resPart = self.unwrapInboundIn(data)
self.responsePartAccumulator.append(resPart)
if case .end = resPart {
self.responseReceivedPromise.succeed(result: self.responsePartAccumulator)
}
}
}
为了完成它，让我们设置客户端的 channel 管道:
let bootstrap = ClientBootstrap(group: group)
.channelInitializer { channel in
let myEventLoop = channel.eventLoop
let sslHandler = try! OpenSSLClientHandler(context: sslContext, serverHostname: hostname)
let http2Parser = HTTP2Parser(mode: .client)
let http2Multiplexer = HTTP2StreamMultiplexer { (channel, streamID) -> EventLoopFuture<Void> in
return myEventLoop.newSucceededFuture(result: ())
}
return channel.pipeline.addHandlers([sslHandler,
http2Parser,
http2Multiplexer,
CreateRequestStreamHandler(multiplexer: http2Multiplexer,
responseReceivedPromise: responseReceivedPromise),
CollectErrorsAndCloseStreamHandler(responseReceivedPromise: responseReceivedPromise)],
first: false).map {
}
}
为了查看一个完整的示例，我将一些东西放在了一个 PR 中 swift-nio-examples/http2-client .
哦，NIO 声称另一端没有正确使用 HTTP/2 的原因是缺少 TLS。没有 OpenSSLHandler，所以 NIO 向远程端传输纯文本 HTTP/2，远程端传输 TLS，然后两个对等点无法相互理解:)。
关于swift - 使用 SwiftNIO 和 SwiftNIOHTTP2 作为 HTTP2 客户端，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53466997/