[ClusterLabs] Antw: [EXT] Colocation per site ?

[Strahil Nikolov]

Hi Ken, can you provide a prototype code example.
Currently,I'm making a script that will be used in a systemd service managed by the cluster.Yet, I would like to avoid non-pacemaker solutions.
Best Regards,Strahil Nikolov 
 
  On Mon, Mar 29, 2021 at 20:12, Ken Gaillot<kgaillot at redhat.com> wrote:   On Sun, 2021-03-28 at 09:20 +0300, Andrei Borzenkov wrote:
> On 28.03.2021 07:16, Strahil Nikolov wrote:
> > I didn't mean DC as a designated coordinator, but as a physical
> > Datecenter location.
> > Last time I checked, the node attributes for all nodes seemed the
> > same.I will verify that tomorrow (Monday).
> > 
> 
> Yes, I was probably mistaken. It is different with scale-out, agent
> puts
> information in global property section of CIB.
> 
> Ideally we'd need expression that says "on node where site attribute
> is
> the same as on node where clone master is active" but I guess there
> is
> no way to express it in pacemaker.

Yep, colocation by node attribute (combined with colocation with
promoted role)

https://clusterlabs.org/pacemaker/doc/en-US/Pacemaker/2.0/html-single/Pacemaker_Explained/index.html#_colocation_properties


> 
> I do not see any easy way to implement it without essentially
> duplicating SAPHanaTopology. There are some attributes that are
> defined
> but never set so far, you may try to open service request to
> implement
> consistent attribute for all nodes on current primary site.
> 
> ...
> 
> Hmm ... agent sets (at least, should set) hana_${SID}_vhost attribute
> for each node and this attribute must be unique and different between
> two sites. May be worth to look into it.
> 
> 
> > Best Regards,Strahil Nikolov
> >  
> >  
> >  On Fri, Feb 19, 2021 at 16:51, Andrei Borzenkov<
> > arvidjaar at gmail.com> wrote:  On Fri, Feb 19, 2021 at 2:44 PM
> > Strahil Nikolov <hunter86_bg at yahoo.com> wrote:
> > > 
> > > 
> > > > Do you have a fixed relation between node >pairs and VIPs? I.e.
> > > > must
> > > > A/D always get VIP1, B/E - VIP2 etc?
> > > 
> > > I have to verify it again, but generally speaking - yes , VIP1 is
> > > always on nodeA/D (master), VIP2 on nodeB/E (worker1) , etc.
> > > 
> > > I guess I can set negative constraints (-inf) -> VIP1 on node B/E
> > > + nodeC/F, but the stuff with the 'same DC as master' is the
> > > tricky part.
> > > 
> > 
> > I am not sure I understand what DC has to do with it. You have two
> > scale-out SAP HANA instances, one is primary, another is secondary.
> > If
> > I understand correctly your requirements, your backup application
> > needs to contact the primary instance which may failover to another
> > site. You must be using some resource agent for it, to manage
> > failover. The only one I am aware of is SAPHanaSR-ScaleOut. It
> > already
> > sets different node properties for primary and secondary sites.
> > Just
> > use them. If you use something else, just look at what attributes
> > your
> > RA sets. Otherwise you will be essentially duplicating your RA
> > functionality because you will somehow need to find out which site
> > is
> > currently primary.
> > 
> > There is no guarantee that pacemaker DC wil be on the same site as
> > SAP
> > HANA primary system.
> >  
> > 
> 
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-- 
Ken Gaillot <kgaillot at redhat.com>

  
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