9:46 a.m.
On Fri, Jun 01, 2018 at 10:33:14AM -0400, Jeff Layton wrote:
On Fri, 2018-06-01 at 10:17 -0400, J. Bruce Fields wrote:
> On Fri, Jun 01, 2018 at 06:42:37AM -0400, Jeff Layton wrote:
> > Thanks for having a look. Hmm...you're right.
> >
> > nn->nfsd4_lease = 90; /* default lease time */
> > nn->nfsd4_grace = 90;
> >
> > nit: We should probably add a #define'd constant for that at some
> > point...but, might this be problematic?
> >
> > In the pessimal case, you might renew your lease just before the server
> > crashes. It then comes back up quickly and starts the grace period. By
> > the time the client contacts the server again the grace period is almost
> > over and you may have very little time to actually do any reclaim.
> >
> > ISTR that when we were working on the server at PD we had determined
> > that we needed around 2 grace periods + a small fudge factor. I don't
> > recall the details of how we determined it though.
>
> OK, I'd be interested in any of that.
>
> If we decide we need a larger grace/lease ratio, we may want to adjust
> default lease down at same time to avoid increasing grace period, as
> that's always an annoyance.
>
I think we just figured that we ought to give the client a full lease
period to reclaim everything, in case it holds a lot of state. You also
need to give it a full lease period to figure out that the server has
rebooted, and then I think we added a few seconds to account for "other
factors" (transport delays and whatnot).
I think it would also be easy to extend it on demand.
So, for example: end the grace period when:
(one lease period has passed *and* we've received no reclaim
request in the last second) *or*
two lease periods have passed
Maybe think about the exact choice of numbers a little.
--b.