aurora: throttle on threads

[morgo]

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[Copilot]

Pull request overview

Adds Aurora-specific throttling capabilities by introducing dedicated throttlers for Aurora commit latency and Aurora “active CPU threads”, plus shared setup wiring that opens a small separate monitoring connection pool to avoid interference with the main migration workload.

Changes:

• Introduce throttler.AuroraSetup to probe for Aurora and assemble Aurora throttlers using a lazily-opened monitor *sql.DB.
• Add two new Aurora throttlers: commit-latency (from performance_schema.global_status) and active-threads (from performance_schema.threads + events_waits_current), each with background polling.
• Update migration runner throttler setup to use the shared Aurora setup and to manage a dedicated monitorDB lifecycle.

Reviewed changes

Copilot reviewed 5 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/throttler/aurora.go	Adds shared Aurora detection + throttler construction helper that returns throttlers + a dedicated monitor pool.
pkg/throttler/aurora_test.go	Tests AuroraSetup “no-op” behavior when disabled, non-Aurora, or probe fails.
pkg/throttler/aurora_commitlatency.go	Implements commit-latency throttler based on Aurora global status counters with delta-based averaging.
pkg/throttler/aurora_commitlatency_test.go	Unit tests for commit-latency sampling, throttling transitions, and BlockWait behavior.
pkg/throttler/aurora_activethreads.go	Implements active-threads throttler using perf-schema thread/wait data and vCPU threshold.
pkg/throttler/aurora_activethreads_test.go	Unit tests for active-threads sampling logic, BlockWait behavior, and probe.
pkg/migration/runner.go	Wires Aurora throttlers via AuroraSetup, adds monitorDB pool, and ensures it’s closed appropriately.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 7 changed files in this pull request and generated 4 comments.