.NET 4.6 HttpResponse.PushPromise方法来管理http/2 PUSH_PROMISE标头 [英] .NET 4.6 HttpResponse.PushPromise methods to manage http/2 PUSH_PROMISE header
问题描述
对于 PUSH承诺
I am a bit confused about PUSH PROMISE http/2 header handling in .NET4.6.
当我看 HttpResponse.PushPromise有两个重载:
接受资源路径的人 public void PushPromise(string path)-假设然后读取资源并将二进制文件发送到客户端.
One that accepts path to resource public void PushPromise(string path) - am assuming resource is then read and binary sent across to client.
第二 public void PushPromise(string path, string method, NameValueCollection headers)接受我无法理解的sting method和NameValueCollection headers.
Second public void PushPromise(string path, string method, NameValueCollection headers) that accepts sting method and NameValueCollection headers which I am failing to understand.
我为什么要在PUSH PROMISE标头内传递方法(假设HttpMethod像GET，POST等)和标头集合?
Why would I want to pass method (assuming HttpMethod like GET, POST, etc) and collection of headers inside PUSH PROMISE header?
推荐答案
通过阅读HTTP/2 规范(第8.2节)，这是我收集的信息:
From reading the HTTP/2 spec (Section 8.2), here is what I gather:
PUSH_PROMISE帧必须是可缓存和安全.您可以选择使用GET和HEAD，因为这是定义为安全和可缓存的仅有的两个http方法.
PUSH_PROMISE frames are required to be cacheable and safe. You have the option of using GET and HEAD, as those are the only two http methods that are defined as both safe and cacheable.
由于需要PUSH_PROMISE帧是可缓存的，因此可以将其添加到Promise中特定的Cache-Control指令. 规范的8.2.2节规定客户拥有可以选择下载承诺的流并拒绝它的选项，我想如果客户发现缓存中具有最新版本的资源，客户端就会这样做.
Since PUSH_PROMISE frames are required to be cacheable, this could be used to add specific Cache-Control directives to the promise. Section 8.2.2 of the spec states that a client has the option to download the promised stream and can refuse it, which I imagine a client would do if it found that it had an up-to-date version of the resource in its cache.
控制缓存是我可以看到为什么传递标头的最明显原因，但是也可能还有其他原因.如果您正在编写自定义客户端，则可以使用某些X-Header向客户端提供其他提示(与缓存无关)，以便它可以决定是否要接受承诺的流.
Controlling caching is the most obvious reason I can see for why you might pass headers, but there may be other reasons as well. If you're writing a custom client, you may use certain X-Headers to provide other hints (that aren't related to caching) to the client so it can decide whether or not it wants to accept the promised stream.
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