[webkit-dev] X-Purpose on prefetching requests

Gavin Peters (蓋文彼德斯) gavinp at chromium.org
Tue Sep 28 09:10:31 PDT 2010

On 28 September 2010 11:58, Alexey Proskuryakov <ap at webkit.org> wrote:
> 28.09.2010, в 07:58, Gavin Peters (蓋文彼德斯) написал(а):
>> Noone has commented on this thread in some time; is this less controversial now?
> I've presented some concerns about the effect of this on enterprise network monitors.
> It it also not really clear what the benefits of the proposed approach are. It's beginning to sound like this header doesn't even help statistics much, and the only practical use is refusing to serve a request under high load. But I suspect that there is not much difference between returning a 5xx response and serving a cached pseudo-static version of a resource. It should be much easier to implement the latter (which lots of servers obviously already do) than to change behavior based on current load.

The header allow high load opt out, as you suggested.  It also allows
general opt-out of prefetching by servers.  Additionally, it is the
only way you'd gather statistics about who has prefetch links
targeting you (from Referer when provided with prefetch).  Without
this header, there is no way at all for servers to gather statistics
on user initiated navigations vs prefetches; with it, you can use
cache-control to make this determination.

I see those as benefits, and I think they're nonzero.  On the cost
side, I see a small increase in the size of prefetch requests (and
that cost is born only by this type of request, not by any other kind)
and the hassle you mentioned in network monitoring.

We can probably agree that the cost of the extra request headers is
minimal, so hopefully that's not a very high hurdle to overcome.

The remaining question then is: how much weight should be given to the
difficulties of network monitoring software authors?

- Gavin

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