Re: [oe] [PATCH] sstate: Add a two character subdirectory to the sstate directory layout

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Thu, 2012-08-02 at 16:14 +0200, Martin Jansa wrote:
> 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.

I'm aware of the problem. The main issue is that we probably need to
start enforcing complete paths for all downloads in DL_DIR, including
http:// urls. This would resolve conflicts like:

SRC_URI = "http://server1.org/somefile.patch \
           http://server2.org/somefile.patch"

where the two files are different. The trouble is it will pretty much
break all the source mirrors :(.

Cheers,

Richard