[server] Add configurable disk write-limit recover gap

[swuferhong]

Purpose

Linked issue: close #3611

Parameterize the DiskUsageMonitor recover gap with server.data-disk.write-limit-recover-gap and set its default value to 0.05.

The recover gap now supports dynamic updates together with server.data-disk.write-limit-ratio. Startup and dynamic config validation now enforce 0 < recover-gap < write-limit-ratio <= 1.0.

Brief change log

Tests

API and Format

Documentation

[Copilot]

Pull request overview

This PR makes the TabletServer disk write-protection hysteresis (“recover gap”) configurable and dynamically updatable, replacing the previous hard-coded 10% gap in DiskUsageMonitor.

Changes:

• Introduces server.data-disk.write-limit-recover-gap (default 0.05) and enforces 0 < recover-gap < write-limit-ratio <= 1.0.
• Updates DiskUsageMonitor/LocalDiskManager to compute recover thresholds from the configured gap and to support dynamic updates of both values.
• Adds/updates validation and tests across server dynamic config, storage, and client IT coverage; updates docs accordingly.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
website/docs/maintenance/configuration.md	Documents the new recover-gap option and updates write-limit-ratio semantics.
fluss-server/src/test/java/org/apache/fluss/server/storage/LocalDiskManagerTest.java	Adds startup validation tests for ratio/gap and disabled mode.
fluss-server/src/test/java/org/apache/fluss/server/storage/DiskUsageMonitorTest.java	Extends tests for configurable recover gap and combined dynamic updates.
fluss-server/src/test/java/org/apache/fluss/server/replica/ReplicaManagerTest.java	Updates expectation/comment to reflect new default recover gap.
fluss-server/src/test/java/org/apache/fluss/server/DynamicConfigChangeTest.java	Adds coordinator/tablet dynamic-config validation coverage for ratio+gap.
fluss-server/src/main/java/org/apache/fluss/server/tablet/TabletServer.java	Updates comment to reflect dynamic disk write-limit configs (ratio + gap).
fluss-server/src/main/java/org/apache/fluss/server/storage/LocalDiskManager.java	Wires new config option, validates ratio+gap together, and reconfigures both dynamically.
fluss-server/src/main/java/org/apache/fluss/server/storage/DiskWriteLimitRatioValidator.java	Removes old single-key validator (ratio-only).
fluss-server/src/main/java/org/apache/fluss/server/storage/DiskWriteLimitConfigValidator.java	Adds cross-field validation for write-limit ratio + recover gap.
fluss-server/src/main/java/org/apache/fluss/server/storage/DiskUsageMonitor.java	Makes hysteresis configurable; supports updating ratio+gap together.
fluss-server/src/main/java/org/apache/fluss/server/DynamicServerConfig.java	Allows server.data-disk.write-limit-recover-gap as a dynamic key.
fluss-server/src/main/java/org/apache/fluss/server/coordinator/CoordinatorServer.java	Registers coordinator-side validation for disk write-limit config.
fluss-common/src/main/java/org/apache/fluss/config/ConfigOptions.java	Adds SERVER_DATA_DISK_WRITE_LIMIT_RECOVER_GAP and updates ratio description/range.
fluss-client/src/test/java/org/apache/fluss/client/admin/FlussAdminITCase.java	Updates IT assertions to match new validation behavior/message.

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[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

[wuchong]

Thanks @swuferhong , I only have one comment.

[swuferhong]

@wuchong comments addressed. PTAL, thanks.

[wuchong]

LGTM.