Support zone based virtual topology assignment algorithm

[MarkGaox]

Issues

• My PR addresses the following Helix issues and references them in the PR description:
  Support zone based virtual topology assignment algorithm #2985

Description

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This PR support zone based virtual topology assignment algorithm. In the rest service, introduced a configurable parameter enabling users to select the desired virtual topology assignment algorithm (e.g.,instance_based or zone_based). Additionally, implemented a zone-based assignment algorithm that directly maps physical zones to virtual zones.

Tests

• The following tests are written for this issue:

 mvn clean install -Dmaven.test.skip.exec=true

mvn test -Dtest=TestVirtualTopologyGroupService,TestFaultZoneBasedVirtualGroupAssignment,TestClusterService,TestVirtualTopologyGroupAssignment,TestClusterAccessor -pl helix-rest

Changes that Break Backward Compatibility (Optional)

• This PR doesn't have backward compatibility issue.

Documentation (Optional)

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(Link the GitHub wiki you added)

Commits

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  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Code Quality

• My diff has been formatted using helix-style.xml
  (helix-style-intellij.xml if IntelliJ IDE is used)

[xyuanlu]

We had an offline discussion.
When a new host joining the cluster, the current behavior of virtual group assignment will recompute the whole virtual topology assignment, causing the whole partition assignment shuffle.
I feel like the ideal behavior should be ore sticky. When new hosts are added, the existing hosts' mapping should not change.

[xyuanlu]

Logic looks good.
I think there are many transient in memory data structure created. We could improve the efficiency and readability. Let's talk offline.

[xyuanlu]

we also build a deep copy in distributeUnassignedZones. I think either this or the one in distributeUnassignedZones can be skipped. (Need to rearrange the code though... for example, moving this in line 75 and remove the one in distributeUnassignedZones)

[xyuanlu]

Generally LGTM. nit comments.

[MarkGaox]

Thanks @xyuanlu for reviewing this PR. It's ready to merge.
Final commit message: Support zone based virtual topology assignment algorithm