Enhance ZkHelixVerifier and its related subclass to take a default wait period

[kaisun2000]

Issues

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

Resolve #1321

Description

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  Due to Need a better way to verify (wait) if the partition assignment converged or not. #526, currently we have random sleep() in the test before verifyByPolling().
  This cause test failure in different environment. Here we enhance ZKHelixVerifier
  family with an option in builder to add a waiting period. To keep it backward
  compatible, without enable this waiting option, the code would behave exactly the
  same as before.

Tests

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None

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Running

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  1. Subject is separated from body by a blank line
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  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)

[jiajunwang]

Many tests (especially WAGED tests) are using StrictMatchExternalViewVerifier. We need to do the same for that too.

Overall, my suggestion is still to add waiting to the specific test case where need it. This generic cooling down logic does not look reasonable to me. The cooldown shall be with the test logic.

One alternative way is that we add a parameter to the verify method that you can specify a cooldown in the caller logic. Could you please consider this solution?

[kaisun2000]

Many tests (especially WAGED tests) are using StrictMatchExternalViewVerifier. We need to do the same for that too.

Overall, my suggestion is still to add waiting to the specific test case where need it. This generic cooling down logic does not look reasonable to me. The cooldown shall be with the test logic.

One alternative way is that we add a parameter to the verify method that you can specify a cooldown in the caller logic. Could you please consider this solution?

I did a search of places using verifyByPolling(). There are between 150 to 200 places.

So shall we have another one called as the following?

public boolean verifyByPolling(long timeout, long period, long cooldown) {

[jiajunwang]

LGTM!

[kaisun2000]

This diff is approve, please help to merge into trunk.

TestBestPossibleExternalViewVerifier would have a default COOL_DOWN period
before verifyByPolling. Due to #526, currently we have randow sleep in the
test before verifyByPolling. We intend to use TestBestPossibeVerifier
instead in our unit test. While keep using BestPossibleExternalViewVerifier
in production code.

[jiajunwang]

This diff is approve, please help to merge into trunk.

TestBestPossibleExternalViewVerifier would have a default COOL_DOWN period
before verifyByPolling. Due to #526, currently we have randow sleep in the
test before verifyByPolling. We intend to use TestBestPossibeVerifier
instead in our unit test. While keep using BestPossibleExternalViewVerifier
in production code.

@kaisun2000 please update the comment, it has diverged from the code change quite a lot. Please do take care of the final comment message, once it is in, we don't have a way to modify except reverting the PR.

There are good reasons that we request the author to confirm the final message, instead of just copy-paste from the PR description. And the author should not copy-paste either.

[kaisun2000]

Good point. I did not realize the previous commit message not applying anymore. Let me update it.

[kaisun2000]

This diff is approved, please help to merge.

Due to #526, currently we have random sleep() in the test before verifyByPolling().
This cause test failure in different environment. Here we enhance ZKHelixVerifier
family with an option in builder to add a waiting period. To keep it backward
compatible, without enable this waiting option, the code would behave exactly the
same as before.