Are parallel ESI fetches on the roadmap?

Jay LaPorte jay at
Mon Oct 20 20:12:09 CEST 2014

> We (as in the core dev team) have discussed parallell ESI as a potential
> 4.1 feature.
> As it is now, we haven't decided on this since HTTP/2.0 needs to be
> catered for as well. I'd expect this to formalise a bit more on the next
> developer meeting in November.

Will notes be published publicly (say, on the wiki) for that? If so, I'll
keep an eye out for them.

> Currently you can perhaps hack/work around this by setting up Varnish as
> a backend to itself. Then the "inner" varnish can give you a slightly
> stale version (enable grace), while a background fetch is kicked off to
> renew the stored object. This should remove most of the extra latency,
> given that you in fact can cache the ESI subresources.

While this would help for some use-cases (a large number of ESI includes to
a relatively small number of repeatedly refreshed resources), it doesn't
make much of a dent in our use-case (a large number of ESI includes to a
more-or-less infinite number of more-or-less static resources that take
some effort to compute initially). I appreciate the tip, though!

> Varnish Software (email: sales at may be able to help
> you out if you are willing to pay for the parallell ESI feature.

I'll drop them a line for more information.

Thanks for the information and suggestions!
Jay LaPorte
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