Add a soft host-tag VM placement preference (affinity processor) - #14083
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nagaboinaramgopal wants to merge 1 commit into
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Add a soft host-tag VM placement preference (affinity processor)#14083nagaboinaramgopal wants to merge 1 commit into
nagaboinaramgopal wants to merge 1 commit into
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Adds a host-tag affinity processor. An affinity group of type "host tag affinity" takes the group name as a host tag; when a member VM is deployed, routing hosts carrying that tag in the VM's zone get their deployment priority raised. It is a preference and not a constraint: no host is ever added to the avoid set, so deployment still succeeds when no tagged host is available, and check() never fails a planned destination. The raised priority is not consulted by automatic DRS. Unit tests cover the three paths: tagged hosts get priority raised (nothing excluded), an empty match is a no-op, and check() returns true.
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Description
Adds a new affinity group processor for a soft host-tag placement preference. A group of type "host tag affinity" uses the group name as a host tag, and when a member VM deploys, hosts in its zone with that tag get a higher deployment priority. It is only a preference: no host is excluded, deployment still works when no tagged host is free, and check() never fails a destination. This is the soft counterpart to the existing strict host tag on service and disk offerings. The raised priority is a planner hint and is not used by automatic DRS.
Types of changes
Feature/Enhancement Scale or Bug Severity
Feature/Enhancement Scale
Bug Severity
Screenshots (if appropriate):
N/A
How Has This Been Tested?
Unit tests cover the three paths: tagged hosts get a higher priority, no matching tag is a no-op, and check() returns true.
Also on a live lab with three KVM hosts in one zone: tagged a single host, created a "host tag affinity" group named after the tag, and deployed. All the VMs in the group landed on the tagged host, and a VM outside the group landed on an untagged host.
How did you try to break this feature and the system with this change?
Deployed with no host carrying the tag: the processor does nothing and the VM still deploys. Ran a VM outside the group to confirm the untagged host was a valid target, so the tag preference is what steered placement, not a lack of options. Since it only raises priority and never excludes a host, a full or missing tagged host cannot block a deployment.