[OE-core] [oe] [PATCH] sstate: Add a two character subdirectory to the sstate directory layout

[Martin Jansa]

On Thu, Aug 02, 2012 at 03:53:35PM +0200, Martin Jansa wrote:
> On Wed, Jul 25, 2012 at 10:09:22PM +0100, Richard Purdie wrote:
> > Currently all sstate files are placed into one directory. This does not scale and
> > causes a variety of filesystem issues. This patch adds a two character subdirectory
> > to the layout (based on the first two characters of the hash) so that files
> > can be split into several directories.
> > 
> > This should help performance of sstate in most cases by avoding creating directories with 
> > huge numbers of files.
> > 
> > The SSTATE_MIRRORS syntax needs updating to account for the extra path element by
> > the addition of a PATH item, for example:
> > 
> > SSTATE_MIRRORS = "file://.* file:///some/path/to/sstate-cache/PATH"
> > SSTATE_MIRRORS = "file://.* http://192.168.1.23/sstate-cache/PATH"
> > 
> > This change also sets the scene for using things like lsb-release in
> > the 
> 
> Is it possible to create 2nd level cache with this?
> 
> I have some server with slow upload but fully populated sstate-cache.
> 
> So on server with faster upload which could be used as offical
> SSTATE_MIRROR for SHR distro I would like to add
> 
> SSTATE_MIRRORS ?= "file://.* http://slow-server/sstate-cache/PATH"
> 
> And then sync my sstate-cache directory to public accessible web root (with rsync).
> 
> Problem is that now sstate-cache has all files in slightly different 
> layout then original sstate-cache on slow server. From what I see I guess 
> it finds URL with correct prefix "sstate-cache/Gentoo-2.1/0d" and downloads it 
> directly to sstate-cache dir (and adds .done)
> 
> OE @ ~/oe-core $ ll sstate-cache/sstate-apr-native-x86_64-linux-1.4.6-r1-x86_64-2-*populate-lic*
> -rw-r--r-- 1 bitbake bitbake 9257 Jul 30 12:31 sstate-cache/sstate-apr-native-x86_64-linux-1.4.6-r1-x86_64-2-0d2ed24b90d50bf83e5fe94536596e50_populate-lic.tgz
> -rw-r--r-- 1 bitbake bitbake    0 Aug  2 15:40 sstate-cache/sstate-apr-native-x86_64-linux-1.4.6-r1-x86_64-2-0d2ed24b90d50bf83e5fe94536596e50_populate-lic.tgz.done
> 
> And then creates symlink in right prefix back to absolute path of sstate-cache/file:
> OE @ ~/oe-core $ ll sstate-cache/Gentoo-2.1/0d/sstate-apr-native-x86_64-linux-1.4.6-r1-x86_64-2-*populate-lic*
> lrwxrwxrwx 1 bitbake bitbake 123 Aug  2 15:40 sstate-cache/Gentoo-2.1/0d/sstate-apr-native-x86_64-linux-1.4.6-r1-x86_64-2-0d2ed24b90d50bf83e5fe94536596e50_populate-lic.tgz -> 
> /OE/oe-core/sstate-cache/sstate-apr-native-x86_64-linux-1.4.6-r1-x86_64-2-0d2ed24b90d50bf83e5fe94536596e50_populate-lic.tgz
> 
> But after sstate-cache directory is rsynced somewhere else and oe-core/sstate-cache is removed, 
> all those symlinks point nowhere and public sstate-cache is unusable.
> 
> Can we have relative paths used in symlinks or even instruct fetcher to download that 
> file directly to right prefix?

2 more ideas:

1) would be great to also download file.sigdata if it exists, to be able
   to compare them when they change even on machine which downloaded
   older sstate file from remote url
2) if the reason for this patch was number of files in shared
   sstate-cache directory, then fetcher creating .done files makes
   number double too (would be fine if fetcher stores all 3 files
   (.tgz, .tgz.sigdata, .tgz.done) in right prefix, or moves them to
   right prefix instead of symlinks.

Cheers,

-- 
Martin 'JaMa' Jansa     jabber: Martin.Jansa at gmail.com
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