neonvm-controller: reimplement IPAM via Manager

[olegbbtr]

New implementation has production-ready performance.

For more details, see https://www.notion.so/neondatabase/RFC-robust-IPAM-1fcf189e0047800e96e0c73b388eebad?source=copy_link

Per-commit review can be done.

[Copilot]

Pull Request Overview

This PR reimplements the IPAM (IP Address Management) system via a new Manager architecture to achieve production-ready performance. The implementation moves from a whereabouts-based approach to a custom Manager that provides better concurrency, metrics, and resource management.

Key changes include:

• Complete IPAM architecture redesign: Replaced whereabouts-based allocation with a custom Manager system that handles IP pools, cooldown periods, and automatic rebalancing
• Enhanced metrics and monitoring: Added comprehensive metrics for tracking IP states (allocated, free, unknown, cooldown) and pool statistics
• Improved API design: Changed from NamespacedName-based identification to UID-based VM identification for better consistency

Reviewed Changes

Copilot reviewed 22 out of 23 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
pkg/neonvm/ipam/manager.go	Core Manager implementation handling IP allocation, release, and pool management
pkg/neonvm/ipam/pool.go	PoolClient for managing IPPool CRD interactions
pkg/neonvm/ipam/metrics.go	Enhanced metrics collection with new GaugeVecFunc support
pkg/neonvm/ipam/config.go	Configuration parsing and IP range management utilities
pkg/neonvm/ipam/ipam.go	Updated IPAM interface to use new Manager architecture
pkg/neonvm/controllers/vm_controller.go	Updated VM controller to use UID-based IPAM calls
pkg/util/metricfunc/metricfunc.go	New utility for function-based Prometheus metrics

Comments suppressed due to low confidence (2)

pkg/neonvm/ipam/manager_test.go:254

• The goroutine does not capture the loop variable manager. This will cause all goroutines to operate on the last value of manager. Use go func(m *Manager) { m.Run(ctx); wg.Done() }(manager) instead.

	}

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[Copilot]

There is a typo in the comment: 'nametwork' should be 'network'.

Suggested change

	// "samplenet-10.11.22.0-24" if nametwork name is `samplenet`
	// "samplenet-10.11.22.0-24" if network name is `samplenet`

[Copilot]

The error message should be 'low IP count must be less than or equal to target IP count' since the validation allows equality (LowIPCount > TargetIPCount is the failing condition).

Suggested change

	return fmt.Errorf("low IP count must be less than target IP count")
	return fmt.Errorf("low IP count must be less than or equal to target IP count")

[Copilot]

The error message should be 'high IP count must be greater than or equal to target IP count' since the validation allows equality (HighIPCount < TargetIPCount is the failing condition).

Suggested change

	return fmt.Errorf("high IP count must be greater than target IP count")
	return fmt.Errorf("high IP count must be greater than or equal to target IP count")