Resolved #4768: Added UUID to VMs

[prydin]

Required for all PRs:

• [ X ] Signed CLA.
• [ X ] Associated README.md updated.
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Resolved #4768: Added UUID to VMs.
BIOS UUIDs are needed to correlate metrics from inside the VM to metrics gathered from vSphere. They were originally not included and users raised this as an issue. This PR addresses that issue and adds code to emit BIOS UUIDs when available.

[danielnelson]

UUIDs can often be problematic because they, by design, have high cardinality. We should think about when the BIOS UUID is unique and when it changes. Is it different each time you start a VM? Does it ever change during the VMs lifetime?

[prydin]

They are the same for the lifetime of the VM. It doesn't change when a machine is restarted.

[prydin]

Any indication as to if/when this will be merged? Will it make it into the next maintenance release?

[danielnelson]

This is a little bit borderline for a patch release since it adds a new tag but I think it is minor enough and the plugin is new enough that we can add it.

[randallt]

@prydin Can you describe the scenario a bit more on why a UUID is required to correlate?

[prydin]

The BIOS UUID is the only identifier that's visible both from the vCenter and from inside the guest OS. On Linux, you can get it using the dmidecode command. I've seen use case where there's a need to correlate metrics from within the guest to what vCenter sees.