[ClusterLabs] Coming in Pacemaker 1.1.17: start a node in standby

[Jehan-Guillaume de Rorthais]

On Tue, 25 Apr 2017 10:33:13 +0200
Lars Ellenberg <lars.ellenberg at linbit.com> wrote:

> On Tue, Apr 25, 2017 at 10:27:43AM +0200, Jehan-Guillaume de Rorthais wrote:
> > On Tue, 25 Apr 2017 10:02:21 +0200
> > Lars Ellenberg <lars.ellenberg at linbit.com> wrote:
> >   
> > > On Mon, Apr 24, 2017 at 03:08:55PM -0500, Ken Gaillot wrote:  
> > > > Hi all,
> > > > 
> > > > Pacemaker 1.1.17 will have a feature that people have occasionally asked
> > > > for in the past: the ability to start a node in standby mode.    
> > > 
> > > 
> > > I seem to remember that at some deployment,
> > > we set the node instance attribute standby=on, always,
> > > and took it out of standby using the node_state transient_attribute :-)
> > > 
> > > As in
> > > # crm node standby ava
> > >   <node id="1" uname="ava">
> > >     <instance_attributes id="nodes-1">
> > >       <nvpair id="nodes-1-standby" name="standby" value="on"/>
> > >       ...
> > >     </instance_attributes>
> > >   </node>
> > >   ...  
> > 
> > This solution seems much more elegant and obvious to me. A cli
> > (crm_standby?) interface would be ideal.
> > 
> > It feels weird to mix setup interfaces (through crm_standby or through the
> > config file) to manipulate the same node attribute. Isn't it possible to set
> > the standby instance attribute of a node **before** it is added to the
> > cluster? 
> > > # crm node status-attr ava set standby off
> > >   <node_state id="1" uname="ava" in_ccm="true" crmd="online"
> > > crm-debug-origin="do_update_resource" join="member" expected="member"> ...
> > >     <transient_attributes id="1">
> > >       <instance_attributes id="status-1">
> > > 	...
> > >         <nvpair id="status-1-standby" name="standby" value="off"/>
> > >       </instance_attributes>
> > >     </transient_attributes>
> > >   </node_state>  
> > 
> > It is not really straight forward to understand why you need to edit a
> > second different nvpair to exit the standby mode... :/  
> 
> Well, you want the "persistent" setting "on",
> and override it with a "transient" setting "off".

Quick questions:

  * is it what happen in the CIB when you call crm_standby?
  * is it possible to do the opposite? persistent setting "off" and override it
    with the transient setting?

> That's how to do it in pacemaker.

OK

> But yes, what exactly has ever been "obvious" in pacemaker,
> before you knew?  :-)        (or HA in general, to be fair)

Sure, the more I dig, the more I learn about it...