Simplify InstanceMonitor metric reset to eliminate thread overhead

[LZD-PratyushBhatt]

Issues

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  Simplify InstanceMonitor metric reset to eliminate thread overhead

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Description

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Removed the delayed gauge-reset mechanism that previously created per-instance threads. Earlier, whenever an instance’s operation changed, the system scheduled a background task to reset other operation gauges after a 2-minute delay. In clusters with ~10,000 instances, this resulted in excessive thread creation and contributed to OutOfMemoryError conditions due to hitting thread limits.

The new implementation performs all non-current operation gauge resets immediately and synchronously when an operation change is detected. This removes all thread creation, delayed tasks, and executor-management overhead while preserving the intended behavior of tracking per-instance operation durations.

Only the currently active operation gauge will show a non-zero duration. When an operation changes, all other operation gauges are reset to zero instantly, and the new operation begins timing from its start

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Code Quality

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