config: add scan limit debug config

[asddongmen]

What problem does this PR solve?

Issue Number: close #1638

What is changed and how it works?

When starting the CDC server, you can use the following configuration to limit the scanning speed of the eventBroker.

[debug]
[debug.event-service]
scan-limit-in-bytes = 1048576

Check List

Tests

• Manual test (add detailed scripts or steps below)

Questions

Will it cause performance regression or break compatibility?

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

Release note

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[gemini-code-assist]

Summary of Changes

Hello @asddongmen, 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 introduces a new debug configuration option to control the scan limit for the event service. Previously, this limit was a hardcoded constant, but now it can be configured, providing more flexibility for debugging and performance tuning of the event processing.

Highlights

• Configuration: Added a new "ScanLimitInBytes" field to the "EventServiceConfig" struct in "pkg/config/debug.go", allowing the scan limit for the event service to be configured.
• Event Service Rate Limiting: Modified the "newEventBroker" function in "pkg/eventservice/event_broker.go" to initialize the "scanRateLimiter" using the newly introduced "ScanLimitInBytes" from the debug configuration, replacing a previously hardcoded value.
• Constant Removal: Removed the "maxScanLimitInBytesPerSecond" constant from "pkg/eventservice/dispatcher_stat.go" as its value is now sourced from the configuration.

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[gemini-code-assist]

Code Review

This pull request introduces a new debug configuration ScanLimitInBytes to make the event service scan rate limit configurable, replacing a hardcoded constant. The implementation is straightforward and correct. My only suggestion is to improve the naming of the new configuration field for better clarity, as it represents a rate (bytes per second).

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-08-12 10:32:01.528385511 +0000 UTC m=+349920.562968738: ☑️ agreed by lidezhu.

[asddongmen]

/check-issue-triage-complete

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: flowbehappy, hongyunyan, lidezhu

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Details

Needs approval from an approver in each of these files:

• OWNERS [flowbehappy,hongyunyan,lidezhu]
• pkg/config/OWNERS [flowbehappy]

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