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Memcached Helm Chart - Quick Start Guide

Migration from Bitnami

This chart was created as a drop-in replacement for the Bitnami Memcached chart, using only free and open-source components.

Key Changes from Bitnami:

  1. Image: Official memcached:1.6.39-alpine from Docker Hub
  2. Exporter: prom/memcached-exporter:v0.15.4 from Docker Hub
  3. Service: Headless service by default for StatefulSet pattern
  4. No Dependencies: Removed Bitnami common library

Quick Installation

1. Basic Installation (Single Instance)

helm install my-memcached ./memcached

This creates:

  • 1 Memcached pod
  • Headless service for direct pod access
  • ServiceAccount with minimal permissions

2. Development Installation

helm install memcached-dev ./memcached \
  --set replicaCount=1 \
  --set resources.requests.memory=128Mi \
  --set resources.requests.cpu=100m

3. Production Installation

helm install memcached-prod ./memcached \
  --values values-production.yaml \
  --namespace memcached \
  --create-namespace

4. With Metrics (Prometheus)

helm install memcached ./memcached \
  --set metrics.enabled=true \
  --set metrics.serviceMonitor.enabled=true \
  --set metrics.serviceMonitor.additionalLabels.prometheus=kube-prometheus

Configuration Examples

Configure Memory Limit

helm install memcached ./memcached \
  --set extraArgs[0].name=max-memory \
  --set extraArgs[0].value=1024

This sets Memcached to use 1GB of memory.

High Availability (3 replicas)

helm install memcached ./memcached \
  --set replicaCount=3 \
  --set podAntiAffinityPreset=hard \
  --set resources.requests.memory=512Mi

With Custom Image

helm install memcached ./memcached \
  --set image.registry=my-registry.com \
  --set image.repository=my-memcached \
  --set image.tag=custom-tag

Connecting to Memcached

From Within the Cluster

The headless service provides direct access to each pod:

<release-name>-memcached-headless.<namespace>.svc.cluster.local:11211

Example with release name my-cache in namespace default:

my-cache-memcached-headless.default.svc.cluster.local:11211

Test Connection

# Run a test pod
kubectl run -it --rm memcached-client --image=memcached:1.6.39-alpine -- sh

# Inside the pod, test connection
telnet my-cache-memcached-headless.default.svc.cluster.local 11211

# Try some commands
set test 0 0 5
hello
get test
quit

Upgrading from Bitnami

Option 1: Fresh Installation (Recommended)

  1. Export data if needed (Memcached is a cache, typically okay to lose)
  2. Delete Bitnami release: 
    helm uninstall old-memcached
  3. Install this chart: 
    helm install memcached ./memcached -f my-values.yaml

Option 2: In-Place Migration (Advanced)

  1. Scale down Bitnami deployment: 
    kubectl scale statefulset old-memcached --replicas=0
  2. Install this chart with same release name
  3. Update application connection strings if needed

Monitoring

Enable Metrics

metrics:
  enabled: true
  serviceMonitor:
    enabled: true
    interval: 30s

Access Metrics Manually

kubectl port-forward svc/memcached 9150:9150
curl http://localhost:9150/metrics

Grafana Dashboard

Import Grafana dashboard ID: 37 (Memcached Overview)

Troubleshooting

Check Pod Status

kubectl get pods -l app.kubernetes.io/name=memcached

View Logs

kubectl logs -l app.kubernetes.io/name=memcached

Check Service

kubectl get svc -l app.kubernetes.io/name=memcached
kubectl describe svc memcached-headless

Connect to Pod

kubectl exec -it memcached-0 -- sh

Common Issues

Issue: Pods not starting

# Check events
kubectl describe pod memcached-0

# Common causes:
# - Resource limits too low
# - Image pull issues
# - Security context conflicts

Issue: Cannot connect to Memcached

# Verify service endpoints
kubectl get endpoints memcached-headless

# Test from another pod
kubectl run -it --rm test-pod --image=busybox -- telnet memcached-headless 11211

Advanced Configuration

Custom Arguments

Add Memcached command-line arguments:

extraArgs:
  - name: max-memory
    value: "2048"
  - name: conn-limit
    value: "2048"
  - name: threads
    value: "8"
  - name: max-item-size
    value: "2m"

Security Contexts

Already configured with best practices:

  • Non-root user (UID 11211)
  • Read-only root filesystem
  • Dropped capabilities
  • No privilege escalation

Pod Disruption Budget

Create a PDB for production:

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: memcached-pdb
spec:
  minAvailable: 2
  selector:
    matchLabels:
      app.kubernetes.io/name: memcached

Uninstallation

helm uninstall memcached

To also delete PVCs if persistence was enabled:

kubectl delete pvc -l app.kubernetes.io/name=memcached

Support

For issues and questions:

  • Check the README.md for full configuration options
  • Review values.yaml for all available parameters
  • Consult official Memcached documentation: https://memcached.org/