[ClusterLabs] Pacemaker in puppet with cib.xml?

[Jan Pokorný]

On 21/07/16 13:52 -0500, Ken Gaillot wrote:
> On 07/21/2016 01:35 PM, Stephano-Shachter, Dylan wrote:
>> I want to put the pacemaker config for my two node cluster in puppet
>> but, since it is just one cluster, it seems overkill to use the corosync
>> module. If I just have puppet push cib.xml to each machine, will that
>> work? To make changes, I would just use pcs to update things and then
>> copy cib.xml back to puppet. I am not sure what happens when you change
>> cib.xml while the cluster is running. Is it safe?
> 
> No, pacemaker checksums the CIB and won't accept a file that isn't
> properly signed. Also, the cluster automatically synchronizes changes
> made to the CIB across all nodes, so there is no need to push changes
> more than once.
> 
> Since you're using pcs, the update process could go like this:
> 
>   # Get the current configuration:
>   pcs cluster cib --config > cib-new.xml

As I feel guilty for contributing to this misconception with clufter
"pcs commands" output at one point (also see
https://bugzilla.redhat.com/1328078; still part of the blame
is in pcs I believe: https://bugzilla.redhat.com/1328066),
something has just started screaming in me:

DO NOT USE pcs cluster cib WITH --config LIKE SUGGESTED, BUT RATHER:

    pcs cluster cib > cib-new.xml

>   # Make changes:
>   pcs -f cib-new.xml <whatever-command-you-want>
>   <etc.>

...as otherwise the modifications like this ^ would fail.

>   # Upload the configuration changes to the cluster:
>   pcs cluster cib-push --config cib-new.xml

Note that with cib-push, --config is OK, moreover it's vital as you
really don't want to propagate stale status section and what not
when changing modifying configuration.

Yes, it's counterintuitive to have this asymmetry and it could be
made to work with some added effort at the side of pcs with
the original, disapproved, sequence as-is, but that's perhaps
sound of the future per the referenced pcs bug.
So take this idiom as a rule of thumb not to be questioned
any time soon.

> Using "--config" is important so you only work with the configuration
> section of the CIB, and not the dynamically determined cluster
> properties and status.

(This, apparently, justifies just the cib-push use.)

> 
> The first and last commands can be done on any one node, with the
> cluster running. The "pcs -f" commands can be done anywhere/anytime.

-- 
Jan (Poki)
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