HTTP中的多个响应合法吗? [英] Are multiple responses legal in HTTP?

问题描述

我对HTTP协议的细微差别感到生锈，我想知道它是否可以直接支持发布/订阅?

I'm a bit rusty on nuances of the HTTP protocol and I'm wondering if it can support publish/subscribe directly?

HTTP是请求响应协议.因此，客户端发送一个请求，服务器发送回一个响应. 在HTTP 1.0中，为每个请求建立了新的连接. 现在，HTTP 1.1通过允许客户端保持连接打开并发出多个请求来对HTTP 1.0进行了改进.

HTTP is a request reponse protocol. So client sends a request and the server sends back a response. In HTTP 1.0 a new connection was made for each request. Now HTTP 1.1 improved on HTTP 1.0 by allowing the client to keep the connection open and make multiple requests.

我意识到您可以将HTTP连接升级到websocket，以进行快速的2向通信.我很好奇的是，这是否绝对必要?

I realise you can upgrade an HTTP connection to a websocket for fast 2 way communications. What I'm curious about is whether this is strictly necessary?

例如，如果我请求资源" http://somewhere.com/fetch/me/slowly "

For example if I request a resource "http://somewhere.com/fetch/me/slowly"

服务器是否可以直接直接回复两次? 如先用202接受 然后在准备好内容后不久， 但没有客户端先发送其他请求?

Is the server free to reply directly twice? Such as first with a 202 accepted and then shortly later with the content when it is ready, but without the client sending an additional request first?

即

Client: GET http://somewhere.com/fetch/me/slowly
Server: 202 "please wait..."
Server: 200 "here's your document"

以这种方式实现发布/订阅服务是否正确? 例如:

Would it be correct to implement a publish/subscribe service this way? For example:

Client: http://somewhere.com/subscribe
Server: item 1
...
Server: item 2

我觉得这种可能"有效，因为客户端通常会有一个事件循环监视连接，但是在技术上是错误的(因为遵循该协议的客户端不需要那样实现).

I get the impression that this 'might' work because clients will typically have an event loop watching the connection but is technically wrong (because a client following the protocol need not be implemented that way).

但是，如果您使用分块传输编码，则可以.

However, if you use chunked transfer encoding this would work.

HTTP/2似乎也允许这样做，但是我不清楚是否进行了某些更改以使其成为可能.

HTTP/2 seems to allow this as well but I'm not clear whether something changed to make it possible.

关于发布/订阅，我还没有看到太多讨论，那么如果使用带有或不带有分块编码的纯HTTP/1.1有什么问题怎么办?

I haven't seen much discussion of this in relation to pub/sub so what if anything is wrong with using plain HTTP/1.1 with or without chunked encoding?

如果这行得通，为什么您需要RSS或ATOM之类的东西?

If this works why do you need things like RSS or ATOM?

推荐答案

一个HTTP请求可以具有多个响应"，但是响应都具有1xx范围内的状态码，例如

A HTTP request can have multiple 'responses', but the responses all have statuscodes in the 1xx range, such as 102 Processing.

但是，这些响应只是标题，而不是正文.

However, these responses are only headers, never bodies.

HTTP/1.1(例如之前的1.0)是请求/响应协议.不允许发送未经请求的响应. HTTP/2是一种框架协议，它添加了服务器推送，该协议允许服务器建议报价额外的数据并并行处理多个请求，但不会更改其请求/响应性质.

HTTP/1.1 (like 1.0 before it) is a request/response protocol. Sending a response unsolicited is not allowed. HTTP/2 is a frames protocol which adds server push which allows the server to suggest offer extra data and handle multiple requests in parallel but doesn't change its request/response nature.

可以保持HTTP连接打开并继续发送更多数据.许多(音频，视频)流服务都将使用此功能.

It is possible to keep a HTTP connection open and keep sending more data though. Many (audio, video) streaming services will use this.

但是，这看起来像是一个连续不断的主体，可以持续进行流传输，而不是许多多个HTTP响应.

However, this just looks like a continuous body that keeps on streaming, rather than many multiple HTTP responses.

如果这行得通，为什么您需要RSS或ATOM之类的东西

If this works why do you need things like RSS or ATOM

因为打开TCP连接不是免费的.

Because keeping a TCP connection open is not free.

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