什么是 Http2 中的 GoAway Frame 以及它如何链接到重定向？

Question

我知道Java 9 提供的HTTP/2 客户端，并在尝试使用以下代码的孵化器模块时：

// Request builder
URI uri = new URI("http://www.stackoverflow.com/"); // using www.google.com gives me some payload with no exception
HttpRequest request = HttpRequest.newBuilder().uri(uri).GET().build();

// Client
HttpClient httpClient = HttpClient.newBuilder().followRedirects(HttpClient.Redirect.ALWAYS).build();
System.out.println(httpClient.version());

// Response builder
HttpResponse response = httpClient.send(request, HttpResponse.BodyHandler.asString());

System.out.println("statusCode = " + response.statusCode()); // 200 for google.com

我收到了这个作为输出：

Exception in thread "main" java.io.IOException: /192.168.0.2:60726: GOAWAY received
  at jdk.incubator.httpclient/jdk.incubator.http.Http2Connection.handleGoAway(Http2Connection.java:613)
  at jdk.incubator.httpclient/jdk.incubator.http.Http2Connection.handleConnectionFrame(Http2Connection.java:531)
  at jdk.incubator.httpclient/jdk.incubator.http.Http2Connection.processFrame(Http2Connection.java:466)
  at jdk.incubator.httpclient/jdk.incubator.http.internal.frame.FramesDecoder.decode(FramesDecoder.java:114)
  at jdk.incubator.httpclient/jdk.incubator.http.Http2Connection$FramesController.processReceivedData(Http2Connection.java:152)
  at jdk.incubator.httpclient/jdk.incubator.http.Http2Connection.asyncReceive(Http2Connection.java:425)
  at jdk.incubator.httpclient/jdk.incubator.http.AsyncSSLDelegate.upperRead(AsyncSSLDelegate.java:557)
  at jdk.incubator.httpclient/jdk.incubator.http.internal.common.Queue.put(Queue.java:73)
  at jdk.incubator.httpclient/jdk.incubator.http.AsyncSSLDelegate.asyncReceive(AsyncSSLDelegate.java:503)
  at jdk.incubator.httpclient/jdk.incubator.http.PlainHttpConnection.asyncRead(PlainHttpConnection.java:300)
  at jdk.incubator.httpclient/jdk.incubator.http.PlainHttpConnection$ReadEvent.handle(PlainHttpConnection.java:395)
  at jdk.incubator.httpclient/jdk.incubator.http.HttpClientImpl$SelectorManager.handleEvent(HttpClientImpl.java:438)
  at jdk.incubator.httpclient/jdk.incubator.http.HttpClientImpl$SelectorManager.run(HttpClientImpl.java:408)

向下移动堆栈跟踪，我可以找到GOAWAY列为以下类型之一

jdk.incubator.http.internal.frame.Http2Frame

但是内部类没有太多文档可以找到这种类型代表什么。我也尝试在 JEP 的链接上搜索相同的内容，但找不到任何内容。

问：什么是 GoAway 框架？何时以及如何使用？

问：为什么如果我更改我的代码以使用客户端而不遵循尝试获取“stackoverflow.com”的重定向，我不会收到相同的异常？

HttpClient httpClient = HttpClient.newBuilder().build();

Answer 1

如规格中所规定，

GOAWAY 帧（类型=0x7）用于启动服务器正常关闭连接。

很可能该帧是由服务器在第二个连接上发送的，即重定向之后的那个。

stackoverflow.com 上的所有 URL 都接受 http/2 连接吗？查看我的 HTTP/2-SPDY 浏览器插件的指标时，情况似乎并非如此。