[Pacemaker] ping resource polling skew

[Quentin Smith]

On Wed, 20 Mar 2013, Andreas Kurz wrote:

> On 2013-03-19 17:02, Quentin Smith wrote:
>> Hi-
>>
>> I have my cluster configured to use a cloned ping resource, such that I
>> can write a constraint that I prefer resources to run on a node that has
>> network connectivity. That works fine if a machine loses its network
>> connection (the ping attribute goes to 0, resources migrate to another
>> machine, etc.).
>>
>> However, if instead what happens is the ping /target/ goes offline, it
>> seems that Pacemaker will bounce resources around the cluster, as each
>> node notices that the ping target is unreachable at a slightly different
>> time.
>
> using more than one targets is always a good idea and choose targets
> that are also highly available

Sure, and we have. No choice of ping targets is going to help us if the 
servers are partitioned from the rest of the network, through.

>> Is there any way to get Pacemaker to delay resource transitions until at
>> least one full polling cycle has happened, so that in the event of an
>> outage of the ping target, resources stay put where they are running?
>
> there is the "dampen" parameter .... use a high value like 3 or more
> times the monitor-interval to give all nodes the chance to detect the
> dead target(s), that should help.

Does that actually help in this case? My understanding is that the dampen 
parameter will delay the attribute change for each host, but those delays 
will still tick down separately for each node, resulting in exactly the 
same behavior, just delayed by dampen seconds.

--Quentin

>
> Regards,
> Andreas
>
> -- 
> Need help with Pacemaker?
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>
>>
>> --Quentin
>>
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