[Linux-cluster] clurgmgrd : <notice> relocating a service to better node

[Ryan Mitchell]

On 04/11/2012 04:31 PM, Parvez Shaikh wrote:
> cluster.conf file -
>
>     ....
>     <failoverdomains>
>     <failoverdomain name="my_domain" nofailback="1" ordered="1"
>     restricted="1">
>     <failoverdomainnode name="my_blade2.my_domain" priority="2"/>
>     <failoverdomainnode name="my_blade1.my_domain" priority="1"/>
>     </failoverdomain>
>     </failoverdomains>
>
You have an "ordered" failoverdomain and you have priorities on your 
nodes.  According to the setting above, your preferred node is 
"my_blade1.my_domain".  That means that if the service is running on 
"my_blade2" (2nd-preferred) and "my_blade1" (1st-preferred) transitions 
to available, the service will relocate back onto that node.

More info is available on: man 8 clurgmgrd:
---
        ordered domain : The order specified in the configuration 
dictates the order of preference  of  members  within the  domain.  The  
highest-ranking member of the domain will run the service whenever it is 
online.  This means that if member A has a higher rank than member B, 
the service will migrate to A if it was running  on  B  if  A 
transitions from offline to online.
---

You can stop this behavior by either disabling "ordered" for the 
"my_domain" failover domain or by giving both nodes the same priority in 
their failover domain entries.

However, you also seem to have "nofailback=1" set, which should prevent 
the behavior you describe.  Again from "man 8 clurgmgrd":
---
        nofailback : Enabling this option for an ordered failover domain 
will prevent automated fail-back after a more-preferred node rejoins the 
cluster. Consequently, nofailback requires an ordered domain in order to 
be meaning-ful.  When nofailback is used, the following two behaviors 
should be noted:
         * If a subset of cluster nodes forms a quorum, the node with 
the highest priority in the  failover  domain  is selected  to run a 
service bound to the domain. After this point, a higher priority member 
joining the cluster will not trigger a relocation.
         * When a service is running outside of its unrestricted 
failover domain and a cluster member boots which is  a part  of the 
service's failover domain, the service will relocate to that member. 
That is, nofailback does not prevent transitions from outside of a 
failover domain to inside a failover domain. After this point, a  higher 
priority member joining the cluster will not trigger a relocation.
---

The second point does not apply to your configuration because both nodes 
are in the failover domain.

Can we see some message logs of an event when the service fails over?

Ryan Mitchell
Red Hat Global Support Services
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