[ClusterLabs] Antw: Re: Set a node attribute for multiple nodes with one command
Kostiantyn Ponomarenko
konstantin.ponomarenko at gmail.com
Thu Dec 1 11:09:16 EST 2016
Thank you for the comprehensive answer. =)
Thank you,
Kostia
On Thu, Dec 1, 2016 at 5:56 PM, Ken Gaillot <kgaillot at redhat.com> wrote:
> On 12/01/2016 06:04 AM, Kostiantyn Ponomarenko wrote:
> > OK, now I see. I still have a few questions.
> > 1. Is there a good reason to not remove the attribute totally if it
> > is "deleted"?
>
> We do this for two reasons:
>
> 1. You can "delete" an attribute for just one node, while leaving it on
> other nodes. Attrd needs to remember the attribute as a whole, and just
> delete the value for the one node. Even deleting an attribute on all
> nodes is done by separate deletes for each node, so this matters even then.
>
> 2. Information about the attribute needs to continue to exist in order
> to reliably process changes from different nodes. I forget the exact
> details, but I remember looking into it before.
>
> These limitations could possibly be addressed by keeping the attribute
> but setting a "deleted" flag, and changing how those would be reported,
> but it's not on the radar right now.
>
> > 2. Does "attrd_updater" sets attributes to "status" configuration
> > section only?
>
> Yes (when using corosync 2).
>
> crm_attribute modifies the CIB directly, so there is no way to batch its
> changes with a delay.
>
> > 3. Do I need to modify/set "--delay" to 0 before removing or
> > changing the attribute? Because now I see that previously set delay
> > works when I delete the attribute (--delete).
>
> It depends on what you want. The point of the delay is to write changes
> out to the CIB only every so often, to save disk I/O. If you're
> potentially changing attribute values several times per second, this
> would be a huge performance boost. The delay affects all changes,
> including deletes.
>
> If you want a specific change to be written to the CIB immediately, then
> yes, you have to set the delay to 0. You can either change the delay
> beforehand with attrd_updater --update-delay or change the delay and
> value together with --update-both.
>
> > 4. Does a delay set only one time work until it's unset (set to 0)?
>
> Yes
>
> > Thank you,
> > Kostia
> >
> > On Wed, Nov 30, 2016 at 10:39 PM, Ken Gaillot <kgaillot at redhat.com
> > <mailto:kgaillot at redhat.com>> wrote:
> >
> > On 11/30/2016 11:31 AM, Kostiantyn Ponomarenko wrote:
> > > Hi Ken,
> > >
> > > I didn't look into the logs, but I experimented with it for a
> while.
> > > Here is what I found.
> > >
> > > It worked for you because this attribute - "my-attr" - has not
> ever been
> > > set before in that cluster.
> > >
> > > So if you set an attribute, then remove it, and then set it with
> > > "--delay", like:
> > >
> > > # attrd_updater -N node-0 -n my-attr --update false --delay 20
> > >
> > > , this delay (dampening) won't work.
> >
> > Once set, attributes are not truly deleted -- only their values are
> > cleared. And --delay has no effect with --update if the attribute
> > already exists, which is what you see above.
> >
> > To set a delay on an already existing attribute, you have to use
> > attrd_updater --update-delay or --update-both.
> >
> > > Moreover, when you delete this attribute the actual remove will be
> > > delayed by that "--delay" which was used when the attribute was
> set.
> > >
> > >
> > > Thank you,
> > > Kostia
> > >
> > > On Tue, Nov 29, 2016 at 1:08 AM, Ken Gaillot <kgaillot at redhat.com
> <mailto:kgaillot at redhat.com>
> > > <mailto:kgaillot at redhat.com <mailto:kgaillot at redhat.com>>> wrote:
> > >
> > > On 11/24/2016 05:24 AM, Kostiantyn Ponomarenko wrote:
> > > > Attribute dampening doesn't work for me also.
> > > > To test that I have a script:
> > > >
> > > > attrd_updater -N node-0 -n my-attr --update false
> --delay 20
> > > > sleep 3
> > > > attrd_updater -N node-0 -n my-attr --update true
> > > > sleep 7
> > > > attrd_updater -N node-1 -n my-attr --update true
> > >
> > > This sequence works for me -- the attributes are not written
> > to the live
> > > CIB until the end of the delay, when both are written at the
> > same time.
> > >
> > > The remaining issue must be with the policy engine. You could
> > look at
> > > the detail log on the DC when these changes were made; you
> > should see
> > > info-level messages with the CIB change with both values
> > together (lines
> > > with "cib_perform_op: ++" and the attribute values), then
> > "Transition
> > > aborted" with "Transient attribute change", then a bunch of
> > "pengine:"
> > > lines saying what the cluster wants to do with each resource.
> > >
> > > There should be some information about the scores used to
> > place the
> > > resources.
> > >
> > > >
> > > > All my resources have this rule in Pacemaker config:
> > > >
> > > > crm configure location res1-location-rule res1 \
> > > > rule 0: my-attr eq true \
> > > > rule -inf: my-attr ne true
> > > >
> > > > On a working two-node cluster I remove "my-attr" from both
> > nodes.
> > > > Then run my script. And all resources start on node-0.
> > > > Am I doing something wrong?
> > > > Or maybe my understanding of an attribute dampening is not
> > correct?
> > > >
> > > > My Pacemaker version is 1.1.13. (heh, not the last one, but
> > it is what
> > > > it is ...)
> > > >
> > > > Thank you,
> > > > Kostia
> > > >
> > > > On Wed, Nov 23, 2016 at 7:27 PM, Kostiantyn Ponomarenko
> > > > <konstantin.ponomarenko at gmail.com
> > <mailto:konstantin.ponomarenko at gmail.com>
> > > <mailto:konstantin.ponomarenko at gmail.com
> > <mailto:konstantin.ponomarenko at gmail.com>>
> > > > <mailto:konstantin.ponomarenko at gmail.com
> > <mailto:konstantin.ponomarenko at gmail.com>
> > > <mailto:konstantin.ponomarenko at gmail.com
> > <mailto:konstantin.ponomarenko at gmail.com>>>> wrote:
> > > >
> > > > Maybe I am doing something wrong, but I cannot set
> "status" section
> > > > node attributes to a shadow cib, cluster applies them
> immediately.
> > > > To try it out I do in a console:
> > > >
> > > > crm_shadow --create test
> > > > crm_attribute --type nodes --node node-0 --name
> my-attribute
> > > > --update 1 --lifetime=reboot
> > > >
> > > > And this attribute is set to the live cluster
> configuration immediately.
> > > > What am I doing wrong?
> > > >
> > > > Thank you,
> > > > Kostia
> > > >
> > > > On Tue, Nov 22, 2016 at 11:33 PM, Kostiantyn Ponomarenko
> > > > <konstantin.ponomarenko at gmail.com
> > <mailto:konstantin.ponomarenko at gmail.com>
> > > <mailto:konstantin.ponomarenko at gmail.com
> > <mailto:konstantin.ponomarenko at gmail.com>>
> > > > <mailto:konstantin.ponomarenko at gmail.com
> > <mailto:konstantin.ponomarenko at gmail.com>
> > > <mailto:konstantin.ponomarenko at gmail.com
> > <mailto:konstantin.ponomarenko at gmail.com>>>> wrote:
> > > >
> > > > Ken,
> > > > Thank you for the explanation.
> > > > I will try this low-level way of shadow cib creation
> tomorrow.
> > > > PS: I will sleep much better with this excellent
> news/idea. =)
> > > >
> > > > Thank you,
> > > > Kostia
> > > >
> > > > On Tue, Nov 22, 2016 at 10:53 PM, Ken Gaillot
> > > > <kgaillot at redhat.com <mailto:kgaillot at redhat.com>
> > <mailto:kgaillot at redhat.com <mailto:kgaillot at redhat.com>>
> > > <mailto:kgaillot at redhat.com <mailto:kgaillot at redhat.com>
> > <mailto:kgaillot at redhat.com <mailto:kgaillot at redhat.com>>>> wrote:
> > > >
> > > > On 11/22/2016 04:39 AM, Kostiantyn Ponomarenko
> > wrote:
> > > > > Using "shadow cib" in crmsh looks like a good
> > idea, but it doesn't work
> > > > > with node attributes set into "status" section
> > of Pacemaker config.
> > > > > I wonder it it is possible to make it work
> > that way.
> > > >
> > > > Forgot to mention -- the shadow CIB is probably
> > the best way
> > > > to do this.
> > > > I don't know if there's a way to do it in crmsh,
> > but you can
> > > > use it with
> > > > the low-level commands crm_shadow and
> crm_attribute
> > > > --lifetime=reboot.
> > > >
> > > > > Ken,
> > > > >>> start dampening timer
> > > > > Could you please elaborate more on this. I
> > don't get how I can set this
> > > > > timer.
> > > > > Do I need to set this timer for each node?
> > > > >
> > > > >
> > > > > Thank you,
> > > > > Kostia
> > > > >
> > > > > On Mon, Nov 21, 2016 at 9:30 AM, Ulrich Windl
> > > > > <Ulrich.Windl at rz.uni-regensburg.de
> > <mailto:Ulrich.Windl at rz.uni-regensburg.de>
> > > <mailto:Ulrich.Windl at rz.uni-regensburg.de
> > <mailto:Ulrich.Windl at rz.uni-regensburg.de>>
> > > > <mailto:Ulrich.Windl at rz.uni-regensburg.de
> > <mailto:Ulrich.Windl at rz.uni-regensburg.de>
> > > <mailto:Ulrich.Windl at rz.uni-regensburg.de
> > <mailto:Ulrich.Windl at rz.uni-regensburg.de>>>
> > > > > <mailto:Ulrich.Windl at rz.uni-regensburg.de
> > <mailto:Ulrich.Windl at rz.uni-regensburg.de>
> > > <mailto:Ulrich.Windl at rz.uni-regensburg.de
> > <mailto:Ulrich.Windl at rz.uni-regensburg.de>>
> > > > <mailto:Ulrich.Windl at rz.uni-regensburg.de
> > <mailto:Ulrich.Windl at rz.uni-regensburg.de>
> > > <mailto:Ulrich.Windl at rz.uni-regensburg.de
> > <mailto:Ulrich.Windl at rz.uni-regensburg.de>>>>> wrote:
> > > > >
> > > > > >>> Ken Gaillot <kgaillot at redhat.com
> > <mailto:kgaillot at redhat.com> <mailto:kgaillot at redhat.com
> > <mailto:kgaillot at redhat.com>>
> > > > <mailto:kgaillot at redhat.com
> > <mailto:kgaillot at redhat.com>
> > > <mailto:kgaillot at redhat.com <mailto:kgaillot at redhat.com>>>
> > <mailto:kgaillot at redhat.com <mailto:kgaillot at redhat.com>
> > > <mailto:kgaillot at redhat.com <mailto:kgaillot at redhat.com>>
> > > > <mailto:kgaillot at redhat.com
> > <mailto:kgaillot at redhat.com> <mailto:kgaillot at redhat.com
> > <mailto:kgaillot at redhat.com>>>>>
> > > > > schrieb am 18.11.2016 um 16:17 in Nachricht
> > > > >
> > <d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com>
> > > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com>>
> > > >
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com>
> > > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com>>>
> > > > >
> > > >
> > > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com>
> > > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com>>
> > > >
> > > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com>
> > > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com
> > <mailto:d6f449da-64f8-12ad-00be-e772d8e382ca at redhat.com>>>>>:
> > > > > > On 11/18/2016 08:55 AM, Kostiantyn
> > Ponomarenko
> > > wrote:
> > > > > >> Hi folks,
> > > > > >>
> > > > > >> Is there a way to set a node attribute
> > to the
> > > > "status" section for few
> > > > > >> nodes at the same time?
> > > > > >>
> > > > > >> In my case there is a node attribute
> > which allows
> > > > some resources to
> > > > > >> start in the cluster if it is set.
> > > > > >> If I set this node attribute for say two
> > > nodes in a
> > > > way - one and then
> > > > > >> another, than these resources are not
> > distributed
> > > > equally between these
> > > > > >> two nodes. That because Pacemaker picks
> > the first
> > > > node to with this
> > > > > >> attribute is set and immediately starts
> all
> > > allowed
> > > > resources on it. And
> > > > > >> this is not the behavior i would like
> > to get.
> > > > > >>
> > > > > >> Thank you,
> > > > > >> Kostia
> > > > > >
> > > > > > Not that I know of, but it would be a
> > good feature
> > > > to add to
> > > > > > attrd_updater and/or crm_attribute.
> > > > >
> > > > > With crm (shell) you don't have
> > transactions for
> > > node
> > > > attributes,
> > > > > but for the configuration. So if you add a
> > location
> > > > restriction
> > > > > preventing any resources on your nodes,
> > then enable
> > > > the nodes, and
> > > > > then delete the location restrictions in
> one
> > > > transaction, you might
> > > > > get what you want. It's not elegant, but
> > itt ill do.
> > > > >
> > > > > To the crm shell maintainer: Is is
> > difficult to
> > > build
> > > > transactions
> > > > > to node status changes? The problem I see
> is
> > > this: For
> > > > configuration
> > > > > you always have transactions (requiring
> > > "commit), but
> > > > for nodes you
> > > > > traditionally have non (effects are
> > immediate). So
> > > > you'd need a
> > > > > thing like "start transaction" which
> > requires a
> > > > "commit" or some
> > > > > kind of abort later.
> > > > >
> > > > > I also don't know whether a "shadow CIB"
> > would help
> > > > for the original
> > > > > problem.
> > > > >
> > > > > Ulrich
> > > > >
> > > > > >
> > > > > > You can probably hack it with a dampening
> > > value of a
> > > > few seconds. If
> > > > > > your rule checks for a particular value
> > of the
> > > > attribute, set all the
> > > > > > nodes to a different value first, which
> > will write
> > > > that value and
> > > > > start
> > > > > > the dampening timer. Then set all the
> > > attributes to
> > > > the desired value,
> > > > > > and they will get written out together
> > when the
> > > > timer expires.
>
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