Welcome! Log In Create A New Profile

Advanced

Re: Parallel subrequests for multi-source long polling?

agentzh
November 19, 2009 04:58AM
On Thu, Nov 19, 2009 at 4:54 PM, shaun <nginx-forum@nginx.us> wrote:
>
> Well, I've got everything *almost* working.

Yay!

> Not calling ngx_http_finalize_request on the parent request cost me a couple of hours of debugging mysterious hangs when there were multiple subrequests, but after doing that the hang goes away and the output looks good.

Nice :)

>  So far, it works perfectly if all the requests return immediately, if all the requests error out and if all the requests but one error out.  The only remaining issue I'm having is when there are 2 or more subrequests the main request does return until both subrequests finish.  In my test case, I have one subrequest return after 0.1 seconds and the other after 10 seconds.  It returns the output from the fast request, as expected, but it returns it after 10 seconds.  Very strange.

Yes, I was aware of this and wanted to say you need to cancel the
pending subrequests when one subrequest succeeds.

It's weird that the client sees the response header and body after the
slowest subrequest finishes. It seems that the response has been
buffered in the last few output filters somehow. Please ensure that
you have set b->flush and b->last_buf in your output chain link. These
flags should defeat buffering in most cases.

And still, we have to cancel the pending subrequests, but close the
connection seems a bit overkill especially in the context of HTTP
keepalive.

>
> I'm guessing I need to do something special to cancel the pending subrequests, or possibly force the completion of the parent request regardless of the state of the rest of subrequests.

Indeed.

> I tried calling ngx_http_finalize_request with various rc values on the pending subrequests, hoping to find something that would force the completion, but nothing seemed to work

What rc values have you tried? Can you publish your code?

> (I can get the parent request to close immediately, but that doesn't really help since it hasn't sent the good request's response yet).
>

Try forcibly flushing the buffered response headers and body on the
parent request :)

Cheers,
-agentzh
Subject Author Posted

Parallel subrequests for multi-source long polling?

shaun November 18, 2009 01:30AM

Re: Parallel subrequests for multi-source long polling?

Piotr Sikora November 18, 2009 02:28AM

Re: Parallel subrequests for multi-source long polling?

agentzh November 18, 2009 03:28AM

Re: Parallel subrequests for multi-source long polling?

agentzh November 18, 2009 03:30AM

Re: Parallel subrequests for multi-source long polling?

shaun November 18, 2009 04:22AM

Re: Parallel subrequests for multi-source long polling?

agentzh November 18, 2009 11:30PM

Re: Parallel subrequests for multi-source long polling?

shaun November 19, 2009 03:54AM

Re: Parallel subrequests for multi-source long polling?

agentzh November 19, 2009 04:58AM

Re: Parallel subrequests for multi-source long polling?

agentzh November 19, 2009 06:32AM

Re: Parallel subrequests for multi-source long polling?

shaun November 19, 2009 02:20PM

Re: Parallel subrequests for multi-source long polling?

Piotr Sikora November 19, 2009 03:28PM

Re: Parallel subrequests for multi-source long polling?

shaun November 19, 2009 04:08PM

Re: Parallel subrequests for multi-source long polling?

Piotr Sikora November 19, 2009 05:42PM

Re: Parallel subrequests for multi-source long polling?

shaun November 20, 2009 03:33AM

Re: Parallel subrequests for multi-source long polling?

Piotr Sikora November 20, 2009 04:48AM

Re: Parallel subrequests for multi-source long polling?

agentzh November 20, 2009 05:28AM

Re: Parallel subrequests for multi-source long polling?

shaun November 20, 2009 06:41AM

Re: Parallel subrequests for multi-source long polling?

shaun November 21, 2009 09:12PM

Re: Parallel subrequests for multi-source long polling?

Piotr Sikora November 21, 2009 10:10PM



Sorry, only registered users may post in this forum.

Click here to login

Online Users

Guests: 82
Record Number of Users: 6 on February 13, 2018
Record Number of Guests: 421 on December 02, 2018
Powered by nginx      Powered by FreeBSD      PHP Powered      Powered by MariaDB      ipv6 ready