DAOS-19207 control: check redundancy factor early

[janekmi]

The "multi branch, no rank leaves" testcase got removed since it was unreconcilable with the assumption subtree.Depth() > 2 means performance domains exist. In this case a tree has performance domains defined but its depth is just 2 so there is no way of detecting these performance domains are there.

This assumption is not introduced by this change. But since this assumption takes part in the CompressedFaultDomainTree() call it has to play the same role when the redundancy factor check is re-implemented at this level. The CompressedFaultDomainTree() function serializes the domain tree for lower levels.

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Steps for the author:

• Commit message follows the guidelines.
• Appropriate Features or Test-tag pragmas were used.
• Appropriate Functional Test Stages were run.
• At least two positive code reviews including at least one code owner from each category referenced in the PR.
• Testing is complete. If necessary, forced-landing label added and a reason added in a comment.

After all prior steps are complete:

• Gatekeeper requested (daos-gatekeeper added as a reviewer).

[github-actions]

Ticket title is 'Validate rd_fac on the dmg level to produce a clearer error message'
Status is 'In Review'
Job should run at elevated priority (1)
https://daosio.atlassian.net/browse/DAOS-19207

[daosbuild3]

Test stage Functional Hardware Medium MD on SSD completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18522/3/testReport/

[daosbuild3]

Test stage Functional Hardware Medium Verbs Provider MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-18522/9/execution/node/1329/log

[janekmi]

@kjacque thank you very much for finding time for a quick chat about this PR. I believe it sped up the review significantly. 👍

[daosbuild3]

Test stage Unit Test completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18522/11/testReport/

[kjacque]

This is basically what I was thinking. Thanks! This will make it easier to modify when extending fault domains.

Just a few small things, otherwise looks good.

[daosbuild3]

Test stage Unit Test completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18522/12/testReport/

[daosbuild3]

Test stage Unit Test completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-18522/13/testReport/

[grom72]

Can a tree be unbalanced?

Suggested change

	if level == 0 {
	return 1
	}
	if level == 1 {
	return len(tree.Children)
	}

[janekmi]

No, it cannot.

Regarding your suggestion, please note this is exactly what is the for-loop below for.

[grom72]

Yes, I know, but it is not needed to call each tree leaf only to confirm that it is a leaf and return 1.