Re: http/2 prioritization/fairness bug with proxies
Roberto Peon <grmocg@gmail.com> Fri, 08 February 2013 07:26 UTC
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References: <CAA4WUYjiBZpShKKFfHQnixc94aOLrck0oR4ykARB=hF5h8nkfA@mail.gmail.com> <3430.1359961022@critter.freebsd.dk> <510F72CE.8030003@treenet.co.nz> <CAA4WUYiBJrLjM0-vurFOuJfUaabXtK=W8N5z28yshSfrvD9crg@mail.gmail.com> <1516.1360002578@critter.freebsd.dk> <42A54D15-0AA3-4172-94F7-E94C86E84D7F@niven-jenkins.co.uk> <2346.1360010079@critter.freebsd.dk> <CAA4WUYiyu+JvFuKooqa4xVdCJP=Mngu9dgHjhH99_SEac1kCZQ@mail.gmail.com> <CAOeYYRf6V+oh3ZULG1458wLL-YpgzBJbyQEPiqdo5t_snT=aZQ@mail.gmail.com>
Date: Thu, 07 Feb 2013 23:23:43 -0800
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From: Roberto Peon <grmocg@gmail.com>
To: Ashok Kumar <ashokkumar.j@gmail.com>
Cc: "William Chan (陈智昌)" <willchan@chromium.org>, Poul-Henning Kamp <phk@phk.freebsd.dk>, Ben Niven-Jenkins <ben@niven-jenkins.co.uk>, Amos Jeffries <squid3@treenet.co.nz>, HTTP Working Group <ietf-http-wg@w3.org>
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Subject: Re: http/2 prioritization/fairness bug with proxies
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It should always keep the pipe full, but it should be using small enough frames that it can respond with alacrity to a higher priority resource. So, in generally, the algorithm should be something like: WriteToAStream(): for priority-bucket in active-priority-list: for stream in priority-bucket: if is_readable(stream): outbound.WriteData(stream, 2**14) return other variations are possible, but that is the basic idea. On Thu, Feb 7, 2013 at 9:50 PM, Ashok Kumar <ashokkumar.j@gmail.com> wrote: > On Feb 4, 2013 8:05 AM, "Amos Jeffries" <squid3 <squid3@treenet.co.nz>@<squid3@treenet.co.nz> > treenet.co.nz <squid3@treenet.co.nz>> wrote: > > Priority 1 - user actioned fetch - requires fast answer > > Priority 2 - background/automated fetch in user-visible window - > requires fast answer but treat as bulk traffic. > > Priority 3 - automated software fetch - treat as low-speed traffic. > > Priority 4 - idle software probe - may drop if necessary. > > I still feel fixed priorities have better use, from a server point of > view. The description may need to be tweaked a bit from the user-agent's > needs perspective. A number will always have different meaning from > different clients and server is not best place to guess who is more > important. > > One tangential question, please spare me if this is not the right place. > How is priority supposed to work from a server's perspective. Let's say > Apache has a MaxClient of 1000. Will it stop accepting normal requests > after it has used up 80% quota and will wait for higher priority requests? > May be a trivial implementation detail but this has been bothering me for > sometime and I thought this might help in deciding how priorities should be > sent/interpreted. > > > > > On Tue, Feb 5, 2013 at 7:17 AM, William Chan (陈智昌) <willchan@chromium.org>wrote: > >> I'm sorry if I am unclear in any way. Please continue to >> challenge/question my comments/assertions so I can clarify my position >> as appropriate. >> >> Just to be clear here, I stand by that it's a protocol bug currently. >> I agree with adding more hooks to convey advisory priority semantics. >> That said, "advisory" is open to interpretation. I agree that the >> sender should ultimately be in control of how it orders responses, and >> indeed there are of course many situations where it's best for the >> sender to ignore the advisory priority. Yet, if the advisory priority >> semantics are generally not respected, then clients will not be able >> to rely on them, and will be forced to implement prioritization at a >> higher layer, which suffers from the link underutilization vs >> contention tradeoff I highlighted earlier. >> >> I appreciate the concern that we're adding complexity by introducing >> new semantics. I am arguing that because the existing mechanisms for >> addressing starvation are suboptimal, we should treat this as a >> protocol bug and thus change the protocol in such a way as to fix this >> problem. My suggestion for doing so was adding new priority "grouping" >> semantics. I am hopeful that these new semantics will not introduce an >> inordinate amount of specification, as the primary idea is that the >> current SPDY priority levels would apply within a "group". I think we >> can come up with a way to define a group that will be relatively easy >> to spec. >> >> SPDY/4 introduces other prioritization semantics beyond just grouping, >> but I wanted to focus on this one first, as I believe this is a bug >> that we *need* to fix. The other SPDY/4 priority changes are of a >> performance optimization nature, and I believe they will need to be >> justified by data. I have no plans to raise them up in this group >> until we have said data. >> >> On Tue, Feb 5, 2013 at 5:34 AM, Poul-Henning Kamp <phk@phk.freebsd.dk> >> wrote: >> > Content-Type: text/plain; charset=ISO-8859-1 >> > -------- >> > In message <42A54D15-0AA3-4172-94F7-E94C86E84D7F@niven-jenkins.co.uk>, >> Ben Nive >> > n-Jenkins writes: >> > >> >>So the idea is the protocol contains enough 'hooks' to sufficiently >> >>express the different priorities between & within groups that folks >> >>would like to express but isn't prescriptive about how anyone uses or >> >>implements different prioritisation, scheduling, etc schemes. >> > >> > That was clearly not how the original poster presented it: >> > >> > "I consider all those options as suboptimal, and thus >> > consider this issue to be a protocol bug. Our SPDY/4 >> > prioritization proposal addresses this by [...]" >> > >> > -- >> > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> > phk@FreeBSD.ORG | TCP/IP since RFC 956 >> > FreeBSD committer | BSD since 4.3-tahoe >> > Never attribute to malice what can adequately be explained by >> incompetence. >> >> > > > -- > .- ... .... --- -.- >
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- http/2 prioritization/fairness bug with proxies William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Yoav Nir
- Re: http/2 prioritization/fairness bug with proxi… Mark Nottingham
- Re: http/2 prioritization/fairness bug with proxi… Poul-Henning Kamp
- Re: http/2 prioritization/fairness bug with proxi… Ilya Grigorik
- Re: http/2 prioritization/fairness bug with proxi… Amos Jeffries
- Re: http/2 prioritization/fairness bug with proxi… Mark Nottingham
- Re: http/2 prioritization/fairness bug with proxi… Amos Jeffries
- Re: http/2 prioritization/fairness bug with proxi… Albert Lunde
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… James M Snell
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Poul-Henning Kamp
- Re: http/2 prioritization/fairness bug with proxi… Ben Niven-Jenkins
- Re: http/2 prioritization/fairness bug with proxi… Poul-Henning Kamp
- Re: http/2 prioritization/fairness bug with proxi… Patrick McManus
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Ashok Kumar
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Mike Belshe
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Martin Thomson
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Martin Thomson
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Martin Thomson
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Martin Thomson
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… Yoav Nir
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Amos Jeffries
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Amos Jeffries
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)