garbage-collection.md

Kubernetes Garbage Collection Tuning

Kubelet garbage collection configuration for GistPin Kubernetes clusters.

Overview

Proper garbage collection tuning prevents node pressure, evictions, and performance degradation. The configuration in infrastructure/k8s/kubelet-gc-config.yaml defines thresholds for image GC, container log rotation, and eviction policies.

Image Garbage Collection

Images are garbage collected when disk usage exceeds the high threshold:

Parameter	Value	Description
imageGCHighThresholdPercent	85%	Trigger image GC above this usage
imageGCLowThresholdPercent	80%	Stop image GC at this usage
imageMinimumGCAge	2m	Minimum age before image removal

Container Log Rotation

Parameter	Value	Description
containerLogMaxSize	50Mi	Max log file size before rotation
containerLogMaxFiles	5	Max log files to retain per container

Eviction Thresholds

Hard Eviction (immediate pod termination)

Signal	Threshold
memory.available	< 500Mi
nodefs.available	< 10%
nodefs.inodesFree	< 5%
imagefs.available	< 15%

Soft Eviction (graceful termination)

Signal	Threshold	Grace Period
memory.available	< 800Mi	1m30s
nodefs.available	< 15%	2m
nodefs.inodesFree	< 10%	2m
imagefs.available	< 20%	2m

Reserved Resources

Resources reserved for system and kubelet daemons:

Cgroup	CPU	Memory	Ephemeral Storage
kubelet	200m	512Mi	2Gi
system	100m	256Mi	1Gi

Alerting

Alerting rules in infrastructure/monitoring/gc-alerts.yml:

Alert	Severity	Description
GCHighImageUsage	warning	Image FS > 85%
GCEvictionThreshold	critical	Eviction signal breached
GCMemoryPressure	warning	Memory pressure
GCDiskPressure	warning	Disk pressure

Related Resources

• Kubelet GC Config
• GC Alerting Rules
• Node Alerts