Fix test TestCustomizedViewAggregation

[mgao0]

Issues

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

Fixed #1301

Description

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

This is a temporary work around for the test failure until we have a design for fixing the root cause. Root cause for the failure is #1296.

Tests

• The following tests are written for this issue:

(List the names of added unit/integration tests)

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

Ran suite tests three times, this test didn't fail in any run.
[ERROR] Failures:
[ERROR] TestResourceChangeDetector.testResetSnapshots:431 » ThreadTimeout Method org.t...
[ERROR] TestZkConnectionLost.testLostZkConnection » ThreadTimeout Method org.testng.in...
[ERROR] TestAssignableInstanceManager.testGetAssignableInstanceMap:115 expected: but was:
[INFO]
[ERROR] Tests run: 1173, Failures: 3, Errors: 0, Skipped: 1
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 01:29 h
[INFO] Finished at: 2020-08-21T11:39:34-07:00

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)

[kaisun2000]

What is the root cause?

[mgao0]

What is the root cause?

Please refer to this issue #1296 for the root cause.

[kaisun2000]

From the description of #1296, I still don't quite understand what caused the issue.

So a finalize() from callback handler causing the routingTableProvider to reset and later update see empty snapshot.

So what caused the finalize? which path?

[mgao0]

From the description of #1296, I still don't quite understand what caused the issue.

So a finalize() from callback handler causing the routingTableProvider to reset and later update see empty snapshot.

So what caused the finalize? which path?

When we dropped a customized state type (TYPE_C for example), the associated customized view path and its children nodes for this customized state type is deleted, so the callback handler is finalized. An example for the path would be: /cluster_name/CUSTOMIZEDVIEW/TYPE_C, /cluster_name/CUSTOMIZEDVIEW/TYPE_C/resource_name

[kaisun2000]

From the description of #1296, I still don't quite understand what caused the issue.
So a finalize() from callback handler causing the routingTableProvider to reset and later update see empty snapshot.
So what caused the finalize? which path?

When we dropped a customized state type (TYPE_C for example), the associated customized view path and its children nodes for this customized state type is deleted, so the callback handler is finalized. An example for the path would be: /cluster_name/CUSTOMIZEDVIEW/TYPE_C, /cluster_name/CUSTOMIZEDVIEW/TYPE_C/resource_name

So when customizedview deleting types would cause routingTableProvider listening on the type path to reset(). This is normal flow. But later usage of routingTableProvider would see empty snapshot which is also expected I guess. But in the code, see my comment in the code, where do the deletion happening?

[kaisun2000]

This is a workaround for flaky test. If this one still get flaky. We can also consider disable it till the root cause is fixed,

[mgao0]

This PR is ready to be merged.
Final commit message: Fix test TestCustomizedViewAggregation.