Re: Add a cooperative FS lock to lilypond-book. (issue 555360043 by address@hidden)

[hanwenn]

On 2020/02/26 11:59:14, dak wrote:
> On 2020/02/26 08:28:33, hahnjo wrote:
> > On 2020/02/26 08:19:39, hahnjo wrote:
> 
> > > > On a philosophical level, it is a lilypond-book implementation
detail
> > > > that it can't deal with concurrent invocation, so the
remediation for
> > > > this problem should be in lilypond-book too.
> > > 
> > > Let me disagree: It's an implementation detail of make that it
runs things
> in
> > > parallel. IMHO a build system should ensure that the result of
running with
> > > multiple jobs is the same as a sequential run.
> > 
> > That said: I'm also fine if some other developer accepts this patch.
See my
> > timing data above to get to your own conclusion. After all, my
opinion is just
> > one of a larger range.
> 
> My take on this is that this "implementation detail" of parallel
invocation
> resulting in awkward breakage is something that warrants fixing
irrespective of
> our build system.  All that the UG states here is
> 
> ‘--lily-output-dir=DIR’
>      Write lily-XXX files to directory DIR, link into ‘--output’
>      directory.  Use this option to save building time for documents
in
>      different directories which share a lot of identical snippets.
> 
> It doesn't state at all what happens in cases of contentions.  Fixing
> contentions with a lock is a brute-force solution just not allowing
for
> parallelism, but it is a solution to the contention problem.
> 
> It is not a solution to lilypond-book starting more jobs than Make
knows about. 
> Or to all but one lilypond-book invocation not doing any progress and
blocking
> Make which could instead start other actual single-process tasks.  So
I see this
> patch and its approach as an improvement to lilypond-book.  I don't
see that it
> solves the parallel build carnage: it just scales down the impact from
having to
> choose between complete serialization and database failure.

David, I think you are saying this patch is LGTM - could you be
explicit, so james understands what is going on?

https://codereview.appspot.com/555360043/