[ClusterLabs] Are use of custom meta-attributes not handled by Pacemaker valid?

[Reid Wahl]

On Thu, Feb 27, 2025 at 11:18 AM <alexey at pavlyuts.ru> wrote:
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> Hi All,
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> We have a project where Pacemaker is under the hood and all the high-level business-logic managed by external custom software, mostly by reading and writing cib XML with cibadmin binary.
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> I need to store some extra properties of the managed resources for these business-logic handlers. Pacemaker itself need no this data.
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> I found that if I add custom nvpair element in primitive/meta_attributes to cib xml and store it with cibadmin –replace it seems to be accepted and stored in CIB database without problem. And reading back well keeping this “custom meta-attribute”.
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> Example:
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>       <primitive id="vlan-ens18_10-ens18.10" class="ocf" type="iface-vlan" provider="heartbeat">
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>         <meta_attributes id="vlan-ens18_10-ens18.10-meta_attributes">
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>           <nvpair id="vlan-ens18_10-ens18.10-meta_attributes-custom" name="custom" value="true"/>
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>         </meta_attributes>
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>         <instance_attributes id="vlan-ens18_10-ens18.10-instance_attributes">
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>           <nvpair id="vlan-ens18_10-ens18.10-instance_attributes-vlan_id" name="vlan_id" value="10"/>
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>           <nvpair id="vlan-ens18_10-ens18.10-instance_attributes-vlan_interface" name="vlan_interface" value="ens18"/>
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>           <nvpair id="vlan-ens18_10-ens18.10-instance_attributes-vlan_name" name="vlan_name" value="ens18.10"/>
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>         </instance_attributes>
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>         <operations>
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>           <op name="monitor" interval="10s" timeout="20s" id="vlan-ens18_10-ens18.10-monitor-interval-10s"/>
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>           <op name="start" interval="0s" timeout="30s" id="vlan-ens18_10-ens18.10-start-interval-0s"/>
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>           <op name="stop" interval="0s" timeout="20s" id="vlan-ens18_10-ens18.10-stop-interval-0s"/>
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>         </operations>
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>       </primitive>
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> But the question is: how valid this action is? For now, for future version? Is there a chance that some of Pacekeeper internals or utilities wipe it up or break on it?

Completely valid. This is one of the intended use cases for
meta-attributes. From the Pacemaker Explained documentation:
"In addition to the cluster-defined meta-attributes described above,
you may also configure arbitrary meta-attributes of your own choosing.
Most commonly, this would be done for use in rules. For example, an IT
department might define a custom meta-attribute to indicate which
company department each resource is intended for. To reduce the chance
of name collisions with cluster-defined meta-attributes added in the
future, it is recommended to use a unique, organization-specific
prefix for such attributes."

https://clusterlabs.org/projects/pacemaker/doc/3.0/Pacemaker_Explained/singlehtml/#resource-meta-attributes

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> I will be very grateful for any information on it, thank you in advance!
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> Sincerely,
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> Alex
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-- 
Regards,

Reid Wahl (He/Him)
Senior Software Engineer, Red Hat
RHEL High Availability - Pacemaker