Re: [gentoo-dev] New distfile mirror layout

[Joshua Kinard <kumba@gentoo.org>]

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.

-- 
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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