Are parallel ESI fetches on the roadmap?

Jay LaPorte jay at
Wed Oct 15 15:30:12 CEST 2014

Hello, Varnish-Misc!

(Apologies if this is the wrong mailing list for this question, or if it is
answered elsewhere; neither Google nor the wiki were turning up anything
when I searched.)

It is with some surprise that I today discovered (through benchmarking with
`varnishlog`) that Varnish does not support fetching ESI requests in
parallel. I am in the process of developing an JSON API that makes heavy
use of ESI—a response may commonly contain hundreds of ESI tags to its
constituent parts—and if ESI requests are done serially, uncached (or even
partially uncached) responses take an eternity. (Our use case is such that
the individual parts of a request have a high cache hit rate, but the
requests themselves do not.)

>From looking around the web, it seems that Varnish 4.0 did the preliminary
groundwork to make parallel ESI fetches possible, and that they are a
planned feature:


I was wondering if there was any rough roadmap or ETA for implementing it
already in place, and if so, where I can track it's progress? If there is
not, who should I contact regarding it? (Allocating funds to Varnish in
order to help support this feature is not out of the question depending on
the specifics, and furthermore I'd be very happy to help test it if need

Thanks for any information you can provide!
Jay LaPorte
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