[ovs-dev] [PATCH RFC 39/52] ovn-sbctl: Allow retries by default.

[Miguel Angel Ajo Pelayo]

It makes sense.

As an idea for future improvements (also applicable to the python client
and the ovsdbapp): something that I've found valuable in distributed
systems is the ability to set an exponential retry time (with a ceiling)
because it's a good failsafe mechanism when one of the clients sends some
sort of big/buggy request that it's going to trigger a failure/long
execution time on the server and finally timeout.

The exponential backoff makes it more likely than the server will recover,
or have time to serve other clients.

On Fri, Sep 22, 2017 at 9:48 PM, Ben Pfaff <blp at ovn.org> wrote:

> Thank you for the review.
>
> There isn't currently a way to control the number of retries.  If that
> is a valuable feature, then it could be added.
>
> You can control the timeout for these utilities with the --timeout
> option (or use the "timeout" program from GNU coreutils).
>
> On Thu, Sep 21, 2017 at 01:17:09PM +0200, Miguel Angel Ajo Pelayo wrote:
> > Makes sense. Is there any way to control the number of retries, and the
> > retry time?
> >
> > Acked-by: Miguel Angel Ajo <majopela at redhat.com>
> >
> > On Wed, Sep 20, 2017 at 12:01 AM, Ben Pfaff <blp at ovn.org> wrote:
> >
> > > Most of the OVS database-manipulation utilities (ovn-sbctl, ovn-nbctl,
> > > ovs-vsctl, vtep-ctl) don't retry their connections by default because
> > > they assume that the database is either up or down and likely to stay
> > > that way.  The OVN southbound database, however, is a likely candidate
> > > for high availability clustering, so that even if it appears to be
> > > down for a moment it will be available again soon.  So, prepare for
> > > the clustering implementation by enabling retry by default in
> > > ovn-sbctl.
> > >
> > > Signed-off-by: Ben Pfaff <blp at ovn.org>
> > > ---
> > >  ovn/utilities/ovn-sbctl.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/ovn/utilities/ovn-sbctl.c b/ovn/utilities/ovn-sbctl.c
> > > index 7af5863b08fc..f4452fa6ee85 100644
> > > --- a/ovn/utilities/ovn-sbctl.c
> > > +++ b/ovn/utilities/ovn-sbctl.c
> > > @@ -120,7 +120,7 @@ main(int argc, char *argv[])
> > >      }
> > >
> > >      /* Initialize IDL. */
> > > -    idl = the_idl = ovsdb_idl_create(db, &sbrec_idl_class, false,
> false);
> > > +    idl = the_idl = ovsdb_idl_create(db, &sbrec_idl_class, false,
> true);
> > >      run_prerequisites(commands, n_commands, idl);
> > >
> > >      /* Execute the commands.
> > > --
> > > 2.10.2
> > >
> > > _______________________________________________
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> > >
>