Re: Hashsum mismatch prevention strategies
On Sun, May 20, 2012 at 9:17 PM, Raphael Geissert <geissert@debian.org> wrote:
> Raphael Geissert wrote:
>> Goswin von Brederlow wrote:
>>> But I'm not convinced the number of files to download is actualy the
>>> limiting factor:
>>
>> It isn't, but it adds overhead.
>
> And there wouldn't be as much benefit if http pipelining is really going to
> be disabled.
>
> (why doesn't the ubuntu image include an additional .conf file to disable it
> for the aws mirrors? oh well...)
Actually, they do. [0]
I said they should tell amazon to fix that and i got as a response that
they tried and the response to them was basically "don't care, fix _your_
broken stuff" -- so basically the same respond previous incarnations e.g.
got from squid maintainer (#565555 - even through this has the also usual:
don't pipeline, open more parallel connections instead) or from googles
chromium archive or from a wide range of (also in many other ways broken)
transparent webproxies a user is forced to implicitly use because of his
company/isp/…
(Unfortunately nobody at Google noticed the irony yet that they enable
pipelining in chromium by default ~3 weeks ago, but deliver chromium
over a broken server… not to mention SPDY which has an emphasis on
multiplexing and pipelining…)
In the end apt-get (and friends) breaks unreproducible "sometimes" with
a pretty indistinguishable errormessage, so a user will properly never
understand what is going on. The benefit from pipelining isn't that great
to ratify this - at least in my eyes (after all, high latency connection
with a high bandwidth aren't that common - usually you have low/high or
high/low combination. In the later the benefit from pipelining is easily
eaten up by the size of the files we need to acquire in general).
Also, currently pdiffs aren't downloaded in a pipelineable fashion, so this
isn't even a regression in this regard, but would be an added improvement
in case we come to a point in which pipeline is enabled by default again.
Maybe there is also some extremely clever way to figure out if pipelining is
broken, but i haven't seen a pattern yet. If someone can tell me how i would
be happy to implement it.
Best regards
David Kalnischkies
[0] https://bugs.launchpad.net/ubuntu/lucid/+source/cloud-init/+bug/948461
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