[Twisted-Python] Returning a response for an HTTP query that requires upstream IO.

[Donal McMullan]

This section of the documentation might be what you're looking for:
https://twistedmatrix.com/documents/current/web/howto/web-in-60/asynchronous.html

If the tcp request to your upstream server is using some blocking
(non-twisted) API, you could look into deferToThread.

On Wed, 22 Apr 2020 at 17:17, Go Luhng <goluhng at gmail.com> wrote:

> I'd like to develop a server that maintains a TCP connection to an
> upstream server, and listens for HTTP requests. Upon receiving an HTTP
> request, the server will send a message upstream, wait for a response,
> and return an HTTP response to the client which made the request.
>
> My background is in writing blocking web services, so my natural
> instinct is to write a `get_result_for(query)` method that will take a
> `query` string and return a result from the upstream TCP connection.
>
> I'm not sure whether writing such a method is possible in Twisted,
> since it's basically a blocking method. I suspect I may have to use
> Continuation-Passing Style instead, that is: provide a callback to
> `get_result_for(query, callback)`.
>
> Even if that's the case, how do I return an HTTP response to the HTTP
> client once the query result is available?
>
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