Re: Experiences with HTTP/2 server push

Martin Thomson <> Mon, 15 August 2016 01:19 UTC

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From: Martin Thomson <>
Date: Mon, 15 Aug 2016 11:14:30 +1000
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To: Kazuho Oku <>
Cc: Tom Bergan <>, Stefan Eissing <>, HTTP Working Group <>
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Subject: Re: Experiences with HTTP/2 server push
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On 15 August 2016 at 07:15, Kazuho Oku <> wrote:
> OTOH let me note that a server can also send priority information as
> part of a PUSH_PROMISE frame. This way, the priority tree does not get
> ruined.

I don't think that makes sense.  If the client processes the
PUSH_PROMISE and immediately reprioritizes the push, then the PRIORITY
frame that appears afterwards will be exactly as meaningless or
destructive as anything else.

> Ideally, I think clients should send PRIORITY frames when it finds out
> how the content of a pushed stream is used, so that a server (that
> consider clients to have better understanding of how the resources
> should be prioritized) can respect the updated tree to prioritize the
> pushed streams.

This is good advice.

>>> We are aware of a few servers that update the priority tree like
>>> this, e.g., see Apache's h2_session_set_prio.
>> Stefan, is this right?  See above.
> In case of H2O, we prioritize pushes of certain media types, but that
> is done out of the HTTP/2 prioritization tree. I think that is the way
> to go.

I couldn't parse this.  Do you mean that you ignore the client's
express priorities, or work within the client's priorities?