Re: [gentoo-dev] New distfile mirror layout

[Joshua Kinard <kumba@gentoo.org>]

On 10/19/2019 19:57, Alec Warner wrote:
> On Sat, Oct 19, 2019 at 4:24 PM Joshua Kinard <kumba@gentoo.org> wrote:
> 
>> On 10/18/2019 09:41, Michał Górny wrote:
>>> Hi, everybody.
>>>
>>> It is my pleasure to announce that yesterday (EU) evening we've switched
>>> to a new distfile mirror layout.  Users will be switching to the new
>>> layout either as they upgrade Portage to 2.3.77 or -- if they upgraded
>>> already -- as their caches expire (24hrs).
>>>
>>> The new layout is mostly a bow towards mirror admins, for some of whom
>>> having a 60000+ files in a single directory have been a problem.
>>> However, I suppose some of you also found e.g. the directory index
>>> hardly usable due to its size.
>>>
>>> Throughout a transitional period (whose exact length hasn't been decided
>>> yet), both layouts will be available.  Afterwards, the old layout will
>>> be removed from mirrors.  This has a few implications:
>>>
>>> 1. Users who don't upgrade their package managers in time will lose
>>> the ability of fetching from Gentoo mirrors.  This shouldn't be that
>>> much of a problem given that the core software needed to upgrade Portage
>>> should all have reliable upstream SRC_URIs.
>>>
>>> 2. mirror://gentoo/file URIs will stop working.  While technically you
>>> could use mirror://gentoo/XX/file, I'd rather recommend finally
>>> discarding its usage and moving distfiles to devspace.
>>>
>>> 3. Directly fetching files from distfiles.gentoo.org will become
>>> a little harder.  To fetch a distfile named 'foo-1.tar.gz', you'd have
>>> to use something like:
>>>
>>> $ printf '%s' foo-1.tar.gz | b2sum | cut -c1-2
>>> 1b
>>> $ wget http://distfiles.gentoo.org/distfiles/1b/foo-1.tar.gz
>>> ...
>>>
>>>
>>> Alternatively, you can:
>>>
>>> $ wget http://distfiles.gentoo.org/distfiles/INDEX
>>>
>>> and grep for the right path there.  This INDEX is also a more
>>> lightweight alternative to HTML indexes generated by the servers.
>>>
>>>
>>> If you're interested in more background details and some plots, see [1].
>>>
>>> [1]
>> https://dev.gentoo.org/~mgorny/articles/improving-distfile-mirror-structure.html
>>>
>>
>> So the answer I didn't really see directly stated here is, where do new
>> distfiles need to go //now//?  E.g., if on woodpecker, I currently cp a
>> distfile to /space/distfiles-local.  What is the new directory I need to
>> use?  And if mirror://gentoo/${FOO} is going away, for the new distfiles
>> target, what would be the applicable prefix to use?
>>
> 
> 
> 
> 
>>
>> Directly using devspace seems like a bad idea, IMHO.  Once long ago, we all
>> got chastised for doing exactly that.  Too much possibility of
>> fragmentation
>> as devs retire or package maintainership changes hands.
>>
>> I looked at the whitepaper'ish-like writeup, and I kinda don't like using a
>> hash-based naming scheme on the new distfiles layout.  I really kind prefer
>> breaking the directories up based on the first letter of the distfiles in
>> question, factoring case-sensitivity in (so you'd have 52 top-level
>> directories for A-Z and a-z, plus 10 more for 0-9).  Under each of those
>> directories, additional subdirectories for the next few letters (say,
>> letters 2-3).  Yes, this leads to some orphan cases where a distfile might
>> live on its own, but from a direct navigation standpoint, it's easy to find
>> for someone browsing the distfiles server and easy to predict where a
>> distfile is at.
>>
>> No math, statistical analysis, or deep-rooted knowledge of filesystems
>> behind that paragraph.  Just a plain old unfiltered opinion.  Sometimes, I
>> need to go get a distfile off the Gentoo mirrors, and being able to quickly
>> find it in the mirror root is great.  Having to do hash calculations to
>> work
>> out the file path will be *really* annoying.
>>
> 
> So if you want a tool that "downloads a distfile off of the mirrors" we
> should be able to build such a utility.
> 
> I'm not really sure why that tool needs to be:
> *copy DISTFILENAME*
> wget distilfes.gentoo.org/$PASTE
> 
> It could just `ebuild portageq download $DISTFILENAME or similar.`
> 
> -A

Sometimes, I'm not on a Gentoo system, or even a Linux/Unix platform, when I
go to fetch a distfile.  Could (and have) fetched as such off of Debian's
mirrors before, but Gentoo is what I know and fetching a distfile off of
those mirrors manually was generally very straight forward.

Not a common case, and certainly not a blocker.  I was just pointing out
that hashed-based naming is decidedly a lot less human-friendly.  But,
that's been the general trend for all-things technology these last few years.

-- 
Joshua Kinard
Gentoo/MIPS
kumba@gentoo.org
rsa6144/5C63F4E3F5C6C943 2015-04-27
177C 1972 1FB8 F254 BAD0 3E72 5C63 F4E3 F5C6 C943

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