dm: make binlog event cache configurable

[OliverS929]

What problem does this PR solve?

Issue Number: ref #12410

What is changed and how it works?

Introduces a new configuration option, event-cache-count, for both the Syncer and Validator components. It allows users to control the number of events cached during binlog sync and decoding.

By lowering event-cache-count, users can reduce memory usage in scenarios where binlog processing consumes a significant amount of memory, helping prevent potential OOM issues on the worker.

Default value for both behave the same as before.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

Please refer to [Release Notes Language Style Guide](https://pingcap.github.io/tidb-dev-guide/contribute-to-tidb/release-notes-style-guide.html) to write a quality release note.

If you don't think this PR needs a release note then fill it with `None`.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign benmeadowcroft, gmhdbjd for approval. For more information see the Code Review Process.
Please ensure that each of them provides their approval before proceeding.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• dm/OWNERS
• dm/config/OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[gemini-code-assist]

Summary of Changes

Hello @OliverS929, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the TiFlow DM component by providing a new configuration option, event-cache-count, for both the Syncer and Validator. This configurable parameter allows users to fine-tune the memory consumption associated with binlog event caching, offering a crucial mechanism to mitigate potential Out-Of-Memory errors in scenarios with high binlog processing demands. The default behavior remains unchanged, ensuring backward compatibility.

Highlights

• Configurable Binlog Event Cache: Introduced a new configuration option, event-cache-count, for both the Syncer and Validator components.
• Memory Optimization: This new option allows users to control the number of binlog events cached, which can significantly reduce memory usage during binlog processing.
• OOM Prevention: By lowering the event-cache-count, users can prevent potential Out-Of-Memory (OOM) issues on the worker, especially in memory-intensive scenarios.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request introduces a configurable event-cache-count for the Syncer and Validator, which is a great addition for managing memory usage. The implementation is consistent across the configuration files and the new test case is a good addition.

I have a couple of suggestions to centralize the default value handling to avoid redundancy.

Also, the PR description states that the 'Default value for both behave the same as before', but it seems the default behavior is changed from no caching (EventCacheCount=0) to caching 10240 events. This might be an intended change, but the description should be updated to reflect this to avoid confusion for users upgrading.

[gemini-code-assist]

To centralize default value handling, consider setting the default for EventCacheCount only within the Adjust methods (TaskConfig.adjust and SubTaskConfig.Adjust), and removing it from here. This avoids redundancy and makes it clearer where defaults are applied.

[gemini-code-assist]

To centralize default value handling, consider setting the default for EventCacheCount only within ValidatorConfig.Adjust, and removing it from here. This avoids redundancy and makes it clearer where defaults are applied.

Suggested change

	Mode: ValidationNone,
	EventCacheCount: defaultEventCacheCount,
	Mode: ValidationNone,

[gemini-code-assist]

This check appears to be redundant. SyncerConfig instances are initialized with default values from DefaultSyncerConfig through UnmarshalYAML. Consequently, this check will likely always evaluate to false. It would be cleaner to rely on DefaultSyncerConfig as the single source for defaults and remove this check.

[ti-chi-bot]

@OliverS929: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-verify	cc9fcea	link	true	/test pull-verify
pull-dm-integration-test	cc9fcea	link	true	/test pull-dm-integration-test

Full PR test history. Your PR dashboard.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.

[D3Hunter]

maybe use the same config as syncer, validator shares many config as syncer