[Pacemaker] Re: Understanding rules: location, colocation, order. Using with Master/Slave

[Adrian Chapela]

Serge Dubrouski escribió:
> On Mon, Oct 27, 2008 at 12:07 PM, Adrian Chapela
> <achapela.rexistros at gmail.com> wrote:
>   
>>> Hello!
>>>
>>> I am working on a cluster with a two Master/Slave instances.
>>>
>>> I have: 2 drbd Master/Slave instance, 1 pingd clone instance, 1 group with
>>> Filesystem resource.
>>>
>>> ms-drbd0 is the first Master/Slave
>>> ms-drbd1 is the second Master/Slave
>>> mail_Group is the first group, it depends on ms-drbd0
>>> samba_Group is the second group, it depends on ms-drbd1
>>>
>>> I have the next rules:
>>>
>>> <rsc_order id="mail-drbd0_before_fs0" from="Montaxe_mail" action="start"
>>> to="ms-drbd0" to_action="promote"/>
>>> <rsc_order id="samba-drbd1_before_fs0" from="Montaxe_samba" action="start"
>>> to="ms-drbd1" to_action="promote"/>
>>> (starts Montaxe_mail when ms-drbd0 has been promoted, start Montaxe_samba
>>> when ms-drbd1 has been promoted. These rules are ok, I think)
>>>
>>> <rsc_colocation id="mail_Group_on_ms-drbd0" to="ms-drbd0" to_role="master"
>>> from="mail_Group" score="INFINITY"/>
>>> <rsc_colocation id="samba_Group_on_ms-drbd1" to="ms-drbd1"
>>> to_role="master" from="samba_Group" score="INFINITY"/>
>>> (Run mail_Group only on the master node, run samba_Group on the master
>>> node)
>>>
>>> <rsc_location id="mail:drbd" rsc="ms-drbd0">
>>> <rule id="rule:ms-drbd0" role="master" score="100">
>>>    <expression  attribute="#uname" operation="eq" value="debianquagga2"/>
>>> </rule>
>>> <rule id="mail_Group:pingd:rule" score="-INFINITY" boolean_op="or">
>>>     <expression id="mail_Group:pingd:expr:undefined" attribute="pingd"
>>> operation="not_defined"/>
>>>     <expression id="mail_Group:pingd:expr:zero" attribute="pingd"
>>> operation="lte" value="0"/>
>>> </rule>
>>> </rsc_location>
>>> <rsc_location id="samba:drbd" rsc="ms-drbd1">
>>> <rule id="rule:ms-drbd1" role="master" score="100">
>>>    <expression  attribute="#uname" operation="eq" value="debianquagga2"/>
>>> </rule>
>>> <rule id="samba_Group:pingd:rule" score="-INFINITY" boolean_op="or">
>>>     <expression id="samba_Group:pingd:expr:undefined" attribute="pingd"
>>> operation="not_defined"/>
>>>     <expression id="samba_Group:pingd:expr:zero" attribute="pingd"
>>> operation="lte" value="0"/>
>>> </rule>
>>> </rsc_location>
>>> (Select debianquagga2 as Master and if the node lost its connection take
>>> the score -INFINITY to do failover, it applies to ms-drbd0 and ms-drbd1)
>>>
>>> With this rules all is working very well but the node selected as master
>>> isn't "debianquagga2",   Why could be the reason ?
>>>
>>> I using Heartbeat 2.1.4
>>>
>>>       
>> I have attached the cib xml file. If I delete two groups, Master is
>> debianQuagga2, If not, Master is debianQuagga1.
>>     
>
> That probably has something to do with how scores are counted for
> groups. In your rsc_location rule for masters you have a really low
> score for assigning master role to debianquagga2. It's possible that
> groups outscore them with default values. I'm not sure in that, that's
> just mu guess. You probably can check this with show score scripts.
>   
I will check that, thank you!
> I'd try to assign rsc_location rules to groups, not to master role.
> Your collocation rule will control that groups are on the same nodes
> with the masters. Or you can try to increase your scores from 100 to
> something higher.
>   

Ok, but I need that node be a master before than start group because it 
depends on the master / slave resource, is that possible changing 
collocation ? Could you open my eyes with a simple example ?

>   
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