Refactor high-coupling method into functions in applyEvent for a more testability

[bowenxia]

What changed? Refactored methods in applyEvent to be functions, and make them as historyReplicator parameters

Why? Easier to do unit test

How did you test it?

Potential risks

Release notes

Documentation Changes

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 2.32558% with 42 lines in your changes missing coverage. Please review.

Project coverage is 68.52%. Comparing base (f0f7efd) to head (f092d74). Report is 6 commits behind head on master.

Additional details and impacted files

| [Files](https://app.codecov.io/gh/uber/cadence/pull/6089?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=uber) | Coverage Δ | | |---|---|---| | [service/history/ndc/history\_replicator.go](https://app.codecov.io/gh/uber/cadence/pull/6089?src=pr&el=tree&filepath=service%2Fhistory%2Fndc%2Fhistory_replicator.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=uber#diff-c2VydmljZS9oaXN0b3J5L25kYy9oaXN0b3J5X3JlcGxpY2F0b3IuZ28=) | `16.87% <2.32%> (-0.26%)` | :arrow_down: | ... and [5 files with indirect coverage changes](https://app.codecov.io/gh/uber/cadence/pull/6089/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=uber) ------ [Continue to review full report in Codecov by Sentry](https://app.codecov.io/gh/uber/cadence/pull/6089?dropdown=coverage&src=pr&el=continue&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=uber). > **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=uber) > `Δ = absolute (impact)`, `ø = not affected`, `? = missing data` > Powered by [Codecov](https://app.codecov.io/gh/uber/cadence/pull/6089?dropdown=coverage&src=pr&el=footer&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=uber). Last update [f0f7efd...f092d74](https://app.codecov.io/gh/uber/cadence/pull/6089?dropdown=coverage&src=pr&el=lastupdated&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=uber). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=uber).

[coveralls]

Pull Request Test Coverage Report for Build 018fe0a0-cddd-4e8a-9e06-8a5a8650a29c

Details

• 43 of 43 (100.0%) changed or added relevant lines in 1 file are covered.
• 171 unchanged lines in 13 files lost coverage.
• Overall coverage decreased (-0.1%) to 69.685%

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Files with Coverage Reduction	New Missed Lines	%
common/task/weighted_round_robin_task_scheduler.go	1	89.05%
service/history/task/transfer_standby_task_executor.go	2	87.14%
common/persistence/sql/sqlplugin/mysql/task.go	2	73.68%
service/frontend/api/handler.go	2	62.56%
service/history/task/transfer_active_task_executor.go	2	72.79%
common/util.go	2	91.78%
common/persistence/sql/sqlplugin/mysql/db.go	2	79.49%
common/task/fifo_task_scheduler.go	3	84.54%
common/archiver/filestore/historyArchiver.go	4	80.95%
service/matching/tasklist/task_list_manager.go	4	76.09%
<!--	Total:	171		-->

Totals
Change from base Build 018fe051-df14-4702-b515-0388c6db07f3:	-0.1%
Covered Lines:	103093
Relevant Lines:	147942

---

💛 - Coveralls