[SR-Users] Processing Async HTTP Requests in Real-time

[Alex Balashov]

A little more helpfully, perhaps:

- By default, a transaction is not created until t_relay(); if you want `http_async_client` to preserve any transaction-affiliated information, you’ll need to create it explicitly with t_newtran() beforehand;

- Only transaction-persistent information is recoverable once the reply is received and the transaction is resumed. $[x]avp’s should be available, since they are transaction-persistent, but $var()s will not be; $var()s are used for individuated message processing, although scoped to the worker process into which the message lands.

- A common pattern for passing relatively more sophisticated, nonscalar data sets, or bits of state, into the other side of the async HTTP reply is to store some kind of payload in `htable`, keyed by `$http_req_id`.

— Alex

> On Aug 18, 2022, at 5:50 PM, Brett Nemeroff <brett+kamailio at voicefoxtelephony.com> wrote:
> 
> Hello Kamailio Team!
> 
> I've tried following the documentation for http_async_query() with suspend=1 and not getting results I'm expecting. Perhaps I'm misunderstanding the documentation. 
> 
> Basically I'm performing a http_async_query() with suspend set to 1 and a "route_name" set to HTTP_REPLY. 
> 
> When my query executes, it appears that Kamailio stops processing in that route block, suspends, and then when a reply is available, it continues in HTTP_REPLY. That makes sense. I pull the return value and set some $var and $avp. When I get to the end of the HTTP_REPLY block, I'm EXPECTING it to RESUME FROM the suspended location from the original route block, which it does NOT seem to do. Is that expected? 
> 
> For what it's worth, I did test just continuing my route logic in HTTP_REPLY and just forgetting about the original route block (moved all the remaining processing logic into HTTP_REPLY) However, existing $avp and $vars that were already set within the transaction were not set. So that's not possible either. 
> 
> I'm pretty sure there is a right way to do this without getting hacky. Can someone help me out? 
> 
> And yes, I know what I'm trying to do sounds like sync, but I want async to handle high volume and the potential for my external URL to lightly block. I believe the right way to do this is with async+suspending. 
> 
> Thank you,
> Brett
> 
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-- 
Alex Balashov | Principal | Evariste Systems LLC

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