Understanding NGX_HTTP_SUBREQUEST_WAITED

[Brian Moran]

I am trying to understand the use of NGX_HTTP_SUBREQUEST_WAITED in the
context of a filter that issues multiple sub-requests. I'm starting with the
ngx_zip_module by Evan Miller; if I construct a recipe for an archive that
has 100 files in it (each file is on an upstream server), I see that a large
number (approaching 100 :-) ) of connections are opened to the upstreams
simultaneously.

Changing the call to ngx_http_subrequest to use NGX_HTTP_SUBREQUEST_WAITED
as the args parameter, recompiling, and restarting,  I still see a large
number of open connections simultaneously to the backends -- it's unclear
that subrequests are being serialized, or that there was any change in
behavior.

How can I determine if indeed the connections are being serialized vs. done
in parallel?

Thanks,
Brian Moran
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