[libvirt PATCH] qemu: Shorten domain name in virtiofsd log path

[Daniel P. Berrangé]

On Thu, Apr 07, 2022 at 03:19:27PM +0200, Martin Kletzander wrote:
> On Thu, Apr 07, 2022 at 02:14:30PM +0200, Ján Tomko wrote:
> > On a Thursday in 2022, Martin Kletzander wrote:
> > > This helps when starting domains with long names which could possibly end up
> > > creating too long of a name for the filesystem.
> > > 
> > > The path is not being saved in the domain config, so there is no need for
> > > backwards compatibility.  User aliases will always start with "ua-" and the only
> > > way paths could collide is to:
> > > 
> > > 1) create a domain named e.g. "asdf-ua"
> > > 2) start the domain with virtiofsd debug logs
> > > 3) destroy the domain
> > > 4) restart libvirt daemon for domain IDs to start from 1 again
> > > 5) create a domain named "asdf"
> > > 6) add user alias for the virtiofs that is the same as was generated for the
> > >   first domain, with the required "ua-" prefix
> > > 7) start the "asdf" domain
> > > 
> > > at which point the logs for the two domains would end up in the same logfile.
> > 
> > > Since this is still better than what we had before I think it is not worth
> > > fixing this peculiar scenario in this patch.
> > > 
> > 
> > I don't think this is better. It does fix it for the strange use case
> > of using very long domain names, and I agree that people combining
> > domain names with "-ua" suffixes and no user aliases along with
> > exact same domain names without the -ua suffix, but using user aliases
> > are not worth worrying about.
> > 
> > But for the 99 % of reasonable users, this patch includes the domain ID
> > in the log path, so the path can change across restarts of the same domain.
> > I don't like including this transient identifier in the log path.
> > We also don't shorten the domain log, since we expect it to stay after
> > the domain stops running.
> > 
> 
> I think it is even better.  If you are looking at the virtiofsd debug
> log then you probably want to look at the current run, you can see when
> the file was created and open the newest one.  And if you need to look
> at all the log files, then you can just:
> 
> cat $(ls -cr *-$domain-$alias-virtiofsd.log) | less
> 
> or similar.  But maybe my assumption about virtiofsd debug logs being
> usable only in corner case scenarios is wrong.
> 
> I wouldn't hate domain logfiles including the id either.

That would lead to a big growth in the number of log files, as we
would be creating a new one every time, instead of appending to
the existing one. 


With regards,
Daniel
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