[SSSD] NSS: disable midpoint refresh for netgroups if ptask refresh is enabled
Pavel Reichl
preichl at redhat.com
Wed Apr 16 13:20:41 UTC 2014
On Mon, 2014-04-14 at 16:32 +0200, Jakub Hrozek wrote:
> On Wed, Apr 09, 2014 at 08:07:25PM +0200, Pavel Reichl wrote:
> > On Mon, 2014-04-07 at 19:07 +0200, Jakub Hrozek wrote:
> > > On Thu, Feb 27, 2014 at 05:15:00PM +0100, Pavel Reichl wrote:
> > > > On Thu, 2014-02-27 at 11:55 +0100, Pavel Březina wrote:
> > > > [snip]
> > > > > Nack.
> > > > > It is still possible having a netgroup expired if
> > > > > refresh_expired_interval is misconfigured (> entry_cache_timeout). Thus
> > > > > you still need to check if the netgroup is valid, maybe throw a visible
> > > > > warning if it is expired and periodic refresh is enabled.
> > > > >
> > > > [snip]
> > > >
> > >
> > > Reviving another stalled thread :-)
> > >
> > > > So how about checking that:
> > > >
> > > > refresh_expired_intervat < entry_cache_timeout
> > >
> > > Are you proposing to abort startup in this case? That sounds like a bit
> > > too heavy solution..
> >
> > No, I would rather log loudly about this problem and then I would set
> > refresh_expired_interval to entry_cache_timeout * 3/4 as is advised in
> > man pages. And again I would log this action loudly.
>
> That would work for me. I don't think we should over-engineer the
> solution, after all, the goal was to make it clear to the admin that
> they need to tune the config themselves..
>
> >
> > >
> > > >
> > > > when configuration is loaded?
> > > >
> > > > I thing these values are never changed although they are not const.
> > >
> > > Yeah, I'm not worried about these values changing at runtime.
> > >
> > > In general I see the point of your patch in that the netgroups are only
> > > ever refreshed by the periodical task and no refreshes are scheduled by
> > > the nss frontend..
> >
> > I'm sorry, I'm not sure I fully understand - by 'point of my patch' you
> > actually mean 'problem of my patch'?
>
> What I meant is that this addition:
> + if (req_type == SSS_DP_NETGR &&
> + dctx->domain->refresh_expired_interval != 0) {
> + ret = EOK;
>
> Makes sense as well to me, because this way neither midpoint refresh nor
> expired record request would be scheduled. What I'm not sure about is --
> would we expand this condition in the future when we add more background
> refresh types?
I can't see why we couldn't :-).
I just think that in the case we add some more refresh types we should
update man page regarding advise on how to set safe value for
refresh_expired_interval.
Something like:
- You can consider setting this value to 3/4 * entry_cache_timeout
+ You can consider setting this value to 3/4 *
+ min(entry_cache_netgroup_timeout, entry_cache_xxx_timeout,...)
And customize computation of safe value in case of misconfiguration
accordingly.
>
> >
> > >
> > > btw can we get into this situation where the refresh is on but a netgroup
> > > is expired even without misconfiguration? For instance if a netgroup was
> > > saved to the cache right before the backend was about to schedule the
> > > periodic task, then before the next task the netgroup was requested and
> > > already expired? Is it OK in this case to just return stale data and let
> > > the next periodic update refresh the netgroup? I think so, because the
> > > cache would eventually converge..
> > I'm not sure about this, I'll run some tests tomorrow and I'll let you
> > know.
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