Re: sharing sstate in bitbake-setup

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

On Wed, 2025-11-26 at 17:13 +0100, Alexander Kanavin wrote:
> On Tue, 25 Nov 2025 at 14:54, Alexander Kanavin via
> lists.yoctoproject.org <alex.kanavin=gmail.com@lists.yoctoproject.org>
> wrote:
> > BB_HASHSERVE_SHARED_DB = "/path/to/common/hashserv.db"
> > 
> > bitbake-setup would put this (and SSTATE_DIR) into site.conf that is
> > symlinked into every build.
> 
> I quickly hacked bitbake's cooker.py to try this out:
> 
> -                dbfile = (self.data.getVar("PERSISTENT_DIR") or
> self.data.getVar("CACHE")) + "/hashserv.db"
> +                dbfile = "/home/alex" + "/hashserv.db"
> 
> 
> And then made two build directories with shared SSTATE_DIR.
> 
> TL;DR: everything ran smoothly and as expected.
> 
> I ran overlapping builds, added no-ops to gnu-config recipe to 'force'
> hash equivalency, and there were no errors or crashes, and sstate was
> reused as expected.
> 
> So I think we should do it like this, subject to 'shared-sstate'
> setting in bitbake-setup, on by default.

PERSISTENT_DIR is *not* designed to be shared between builds. it might
happen to work but is a really bad idea. Personally, I think those
cache directory variables and cache layout need redesigning so we
should probably take the opportunity to do that.

Cheers,

Richard