Only build property key path on construction

[GrantPSpencer]

Issues

• My PR addresses the following Helix issues and references them in the PR description:

Performance improvement

Description

• Here are some details about my PR, including screenshots of any UI changes:

Currently, PropertyKey path is built on every call to PropertyKey.getPath() and performs regex match. This can be expensive and redundant as when we add a listener, we loop through the existing handlers and call propertyKey.getPath() for every handler that exists. The performance hit will be most noticeable in clusters with a large instance count.

Technically, this will make it so that PropertyKey.getPath() will no longer update after instantiation if the underlying PropertyPathBuilder's templateMap is updated. However, I did not find this being done anywhere in the code so in effect there should be no change

Flame graph from 5 minute CPU profile taken during controller transiting to LEADER for clusters with thousands of instances.

Tests

• The following tests are written for this issue:

None

• The following is the result of the "mvn test" command on the appropriate module:

N/A

Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines. In addition, my commits follow the guidelines from "How to write a good git commit message":
  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)

[junkaixue]

good finding.

[GrantPSpencer]

Pull request approved by: @junkaixue
Commit message: Changes PropertyKey so that it only builds the path once when it is instantiated. PropertyKey.getPath() previously would rebuild the path on every call. This could cause a performance hit as it was performing a regex match each time. getPath now returns the path that was constructed when the PropertyKey object is first instantiated

[GrantPSpencer]

CI failed due to known flaky test testEvacuateWithDisabledPartition(org.apache.helix.integration.rebalancer.TestInstanceOperation)
Tracked by Issue #2906