CPS-chained subrequests with I/O interceptions no longer work in nginx 0.8.21 (Was Re: Custom event + timer regressions caused by the new release)

agentzh agentzh at gmail.com
Wed Oct 28 06:10:04 MSK 2009

On Tue, Oct 27, 2009 at 8:43 PM, Valery Kholodkov
<valery+nginxen at grid.net.ru> wrote:
> The Evan Miller's guide to nginx programming might help you:
> http://www.evanmiller.org/nginx-modules-guide-advanced.html#subrequests-sequential

Unfortunately it won't :)

I read that guide *very carefully* one month ago. It does not cover
subrequests issued from content handler and the use of the
"post_subrequest" parameter of ngx_http_subrequest function.

Subrequests issued from output filters are useful but *not* so useful
if without the capability to be initiated from elsewhere. I would be
very sad if nginx's subrequest model is *that* limited. Luckily I've
had an enjoyable time in parallel subrequests directly issued from the
content handler. And the more powerful (and in many situations more
useful) chained subrequests issued from content handler intermediated
by "post_subrequest" at least *seems* to work before 0.8.21. And
that's what I'm asking here. Is it something just too crazy and too
insane to do in nginx?

Also, as the guide itself has noted, the subrequest model has changed
a lot since then. As far as what has affected me, the model has
changed in the following releases (even without a note it their
ChangeLogs it seems):

   0.7.21, 0.7.46, 0.8.4 and possibly more

The list can never be complete I suppose :)

Testing every release tarball using my own test suite to find when
things dramatically change and coding up #if/#else directives are
tedious, but *maybe* it's worth it :)

Thank you for your suggestion anyway :)


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