AGENTS.md

MachineSet Controller

Replica management for MachineSet CRD

OVERVIEW

Ensures expected number of Machine replicas with consistent provider config; implements delete policies (Random/Oldest/Newest).

WHERE TO LOOK

Task	File	Notes
Reconcile loop	machineset_controller.go	Main reconciliation logic
Delete policy	machineset_delete_policy.go	Random/Oldest/Newest implementations
Replica sync	machineset_replica.go	Scale up/down logic
Machine selection	machineset_selector.go	Label-based machine matching
Test suite	machineset_suite_test.go	Ginkgo envtest setup

CONVENTIONS

• Prefer komega over plain Gomega
• Each test uses *_suite_test.go pattern
• Tests run with --race --trace --timeout=10m
• Delete policy: Never delete machines with Deleting finalizer
• Replica sync: Always check MachineSet status before scaling

ANTI-PATTERNS (THIS PACKAGE)

• NEVER skip status update after replica change
• NEVER delete machines without checking delete policy
• ALWAYS use komega.Eventually() for async state checks
• ALWAYS respect MachineSet.DeletionTimestamp during reconciliation

NOTES

• MachineSet controller does NOT create instances (Machine controller does)
• Delete policy only applies when scaling down
• Machines with machine.openshift.io/deletion-in-progress are protected