Memcached Helm Chart

This Helm chart deploys Memcached on a Kubernetes cluster using free and open-source components.

Introduction

This chart bootstraps a Memcached deployment on a Kubernetes cluster using the Helm package manager.

Key Features

• Free and Open Source: Uses the official Memcached Docker image from Docker Hub
• Headless Service by Default: Enables direct pod-to-pod communication
• No Bitnami Dependencies: Completely independent of Bitnami infrastructure
• Production Ready: Includes security contexts, resource limits, and health checks
• Metrics Support: Optional Prometheus exporter integration using prom/memcached-exporter
• Highly Configurable: Extensive configuration options via values.yaml

Prerequisites

• Kubernetes 1.19+
• Helm 3.8.0+

Installing the Chart

To install the chart with the release name my-memcached:

helm install my-memcached ./memcached

The command deploys Memcached on the Kubernetes cluster with the default configuration. The Parameters section lists the parameters that can be configured during installation.

Uninstalling the Chart

To uninstall/delete the my-memcached deployment:

helm uninstall my-memcached

Key Differences from Bitnami Chart

1. Image Source: Uses official memcached:alpine from Docker Hub instead of Bitnami images
2. Default Service Type: Headless service (ClusterIP: None) for StatefulSet pattern
3. Metrics Exporter: Uses prom/memcached-exporter instead of Bitnami's exporter
4. Simplified Structure: Removed Bitnami-specific helpers and common library dependencies
5. Security First: Enhanced security contexts with read-only root filesystem

Configuration

The following table lists the configurable parameters of the Memcached chart and their default values. All parameters are documented with comments in the values.yaml file.

Global Parameters

Parameter	Description	Default
global.imageRegistry	Global Docker image registry	""
global.imagePullSecrets	Global Docker registry secret names as an array	[]

Common Parameters

Parameter	Description	Default
kubeVersion	Override Kubernetes version detection	""
nameOverride	String to partially override memcached.fullname	""
fullnameOverride	String to fully override memcached.fullname	""
clusterDomain	Kubernetes cluster domain name	cluster.local
commonLabels	Labels to add to all deployed objects	{}
commonAnnotations	Annotations to add to all deployed objects	{}

Memcached Image Parameters

Parameter	Description	Default
image.registry	Memcached image registry	docker.io
image.repository	Memcached image repository	memcached
image.tag	Memcached image tag (immutable tags recommended)	1.6.39-alpine
image.pullPolicy	Image pull policy	IfNotPresent
image.pullSecrets	Memcached image pull secrets	[]

Memcached Configuration Parameters

Parameter	Description	Default
replicaCount	Number of Memcached replicas	1
memcached.allocatedMemory	Maximum memory to use for items in MB	64
memcached.maxItemMemory	Max item size in MB	1
memcached.connectionLimit	Maximum simultaneous connections	1024
memcached.extendedOptions	Extended memory options	modern
memcached.extraExtendedOptions	Additional extended options (extstore auto-configured when persistence enabled)	""
memcached.verbosity	Verbosity level (v, vv, vvv)	v
memcached.port	Memcached port	11211

Authentication Parameters

Parameter	Description	Default
auth.enabled	Enable SASL authentication	false
auth.username	Memcached SASL username	""
auth.password	Memcached SASL password	""
auth.existingSecret	Name of existing secret containing password	""

Persistence Parameters

Parameter	Description	Default
persistence.enabled	Enable persistence using PVC (automatically configures extstore)	false
persistence.storageClass	Persistent Volume storage class	""
persistence.annotations	Additional custom annotations for PVC	{}
persistence.labels	Additional custom labels for PVC	{}
persistence.accessModes	Persistent Volume access modes	["ReadWriteOnce"]
persistence.size	Persistent Volume size (extstore uses 90% of this)	8Gi
persistence.selector	Selector to match existing PV	{}
persistence.mountPath	Path to mount the volume (used for extstore path)	/data

Note: When persistence is enabled, extstore is automatically configured. See Using Extstore section for details.

Deployment Parameters

Parameter	Description	Default
command	Override default container command	[]
extraArgs	Additional command line arguments	[]
podLabels	Extra labels for Memcached pods	{}
podAnnotations	Annotations for Memcached pods	{}
podManagementPolicy	StatefulSet Pod Management Policy	Parallel
priorityClassName	Memcached pods' priorityClassName	""
schedulerName	Name of the k8s scheduler	""
terminationGracePeriodSeconds	Seconds pod needs to terminate gracefully	30
updateStrategy.type	StatefulSet strategy type	RollingUpdate

Autoscaling Parameters

Parameter	Description	Default
autoscaling.enabled	Enable Horizontal Pod Autoscaler	false
autoscaling.minReplicas	Minimum number of replicas	3
autoscaling.maxReplicas	Maximum number of replicas	6
autoscaling.targetCPU	Target CPU utilization percentage	50
autoscaling.targetMemory	Target Memory utilization percentage	50

Pod Scheduling Parameters

Parameter	Description	Default
podAffinityPreset	Pod affinity preset (soft or hard)	""
podAntiAffinityPreset	Pod anti-affinity preset (soft or hard)	soft
nodeAffinityPreset.type	Node affinity preset type	""
nodeAffinityPreset.key	Node label key to match	""
nodeAffinityPreset.values	Node label values to match	[]
affinity	Affinity for pod assignment	{}
nodeSelector	Node labels for pod assignment	{}
tolerations	Tolerations for pod assignment	[]
topologySpreadConstraints	Topology Spread Constraints	[]

Health Check Parameters

Parameter	Description	Default
livenessProbe.enabled	Enable livenessProbe	true
livenessProbe.initialDelaySeconds	Initial delay seconds	30
livenessProbe.periodSeconds	Period seconds	10
livenessProbe.timeoutSeconds	Timeout seconds	5
livenessProbe.failureThreshold	Failure threshold	6
livenessProbe.successThreshold	Success threshold	1
readinessProbe.enabled	Enable readinessProbe	true
readinessProbe.initialDelaySeconds	Initial delay seconds	5
readinessProbe.periodSeconds	Period seconds	5
readinessProbe.timeoutSeconds	Timeout seconds	3
readinessProbe.failureThreshold	Failure threshold	6
readinessProbe.successThreshold	Success threshold	1
startupProbe.enabled	Enable startupProbe	false
customLivenessProbe	Custom livenessProbe override	{}
customReadinessProbe	Custom readinessProbe override	{}
customStartupProbe	Custom startupProbe override	{}

Resource Parameters

Parameter	Description	Default
resources.limits	Resource limits	{}
resources.requests.memory	Memory request	256Mi
resources.requests.cpu	CPU request	250m

Security Context Parameters

Parameter	Description	Default
podSecurityContext.enabled	Enable pod Security Context	true
podSecurityContext.fsGroup	Pod Security Context fsGroup	1001
podSecurityContext.seccompProfile.type	Seccomp profile type	RuntimeDefault
containerSecurityContext.enabled	Enable container Security Context	true
containerSecurityContext.runAsUser	Container runAsUser	11211
containerSecurityContext.runAsNonRoot	Container runAsNonRoot	true
containerSecurityContext.allowPrivilegeEscalation	Allow privilege escalation	false
containerSecurityContext.capabilities.drop	Capabilities to drop	["ALL"]
containerSecurityContext.readOnlyRootFilesystem	Read-only root filesystem	true

Extra Configuration Parameters

Parameter	Description	Default
extraEnvVars	Array with extra environment variables	[]
extraEnvVarsCM	ConfigMap with extra env vars	""
extraEnvVarsSecret	Secret with extra env vars	""
lifecycleHooks	Lifecycle hooks for containers	{}
extraVolumes	Extra volumes for pods	[]
extraVolumeMounts	Extra volume mounts for containers	[]
sidecars	Add additional sidecar containers	[]
initContainers	Add additional init containers	[]

ServiceAccount Parameters

Parameter	Description	Default
serviceAccount.create	Create ServiceAccount	true
serviceAccount.name	ServiceAccount name	""
serviceAccount.automountServiceAccountToken	Auto mount token	false
serviceAccount.annotations	ServiceAccount annotations	{}

Service Parameters

Parameter	Description	Default
service.type	Kubernetes Service type	ClusterIP
service.ports.memcached	Memcached service port	11211
service.nodePorts.memcached	Node port for Memcached	""
service.sessionAffinity	Session affinity	None
service.sessionAffinityConfig	Session affinity config	{}
service.clusterIP	Service Cluster IP	""
service.loadBalancerIP	Service Load Balancer IP	""
service.loadBalancerSourceRanges	Load Balancer sources	[]
service.externalTrafficPolicy	External traffic policy	Cluster
service.annotations	Service annotations	{}
service.extraPorts	Extra ports to expose	[]
service.headless.annotations	Headless service annotations	{}

Metrics Parameters

Parameter	Description	Default
metrics.enabled	Enable Prometheus exporter sidecar	false
metrics.image.registry	Exporter image registry	docker.io
metrics.image.repository	Exporter image repository	prom/memcached-exporter
metrics.image.tag	Exporter image tag	v0.14.4
metrics.image.pullPolicy	Exporter image pull policy	IfNotPresent
metrics.containerPort	Exporter container port	9150
metrics.resources.limits	Exporter resource limits	{}
metrics.resources.requests	Exporter resource requests	{}
metrics.containerSecurityContext.enabled	Enable exporter Security Context	true
metrics.service.type	Exporter service type	ClusterIP
metrics.service.port	Exporter service port	9150
metrics.serviceMonitor.enabled	Create ServiceMonitor for Prometheus Operator	false
metrics.serviceMonitor.namespace	ServiceMonitor namespace	""
metrics.serviceMonitor.interval	Scrape interval	30s
metrics.serviceMonitor.scrapeTimeout	Scrape timeout	""

RBAC Parameters

Parameter	Description	Default
rbac.create	Create RBAC resources	true
rbac.rules	Additional rules for ClusterRole	[]
rbac.roleRules	Additional rules for Role	[]

Network Policy Parameters

Parameter	Description	Default
networkPolicy.enabled	Enable NetworkPolicy	false
networkPolicy.allowIngress	Allow inbound traffic	true
networkPolicy.allowEgress	Allow outbound traffic	false
networkPolicy.podSelector	PodSelector for NetworkPolicy	{}
networkPolicy.ingress	Array of ingress rules	See values.yaml
networkPolicy.egress	Array of egress rules	See values.yaml

For a complete list of all parameters with detailed comments, please refer to the values.yaml file.

Examples

Basic Installation

helm install my-memcached ./memcached

With Custom Memory Limit

helm install my-memcached ./memcached \
--set extraArgs[0].name=max-memory \
--set extraArgs[0].value=512

With Metrics Enabled

helm install my-memcached ./memcached \
--set metrics.enabled=true \
--set metrics.serviceMonitor.enabled=true

High Availability Setup

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

With Persistence

helm install my-memcached ./memcached \
--set persistence.enabled=true \
--set persistence.size=10Gi

Using Extstore (Persistent Disk-Backed Cache)

Memcached's extstore feature allows extending the cache beyond available RAM by using disk storage. This chart automatically configures extstore when persistence is enabled.

Automatic Extstore Configuration

When you enable persistence, the chart automatically:

1. Calculates extstore size as 90% of persistence.size (to allow filesystem overhead)
2. Sets ext_path to {persistence.mountPath}/extstore:{calculated_size}G
3. Adds ext_wbuf_size=16 for optimal write performance
4. Mounts the persistent volume at the specified path

Example: Enabling Extstore

helm install my-memcached ./memcached \
--set persistence.enabled=true \
--set persistence.size=100Gi \
--set memcached.allocatedMemory=2048

This will configure:

• 2GB RAM cache (allocatedMemory)
• ~90GB disk-backed cache (extstore, automatically calculated)
• Total effective cache: ~92GB

Advanced Extstore Options

You can add additional extstore options via memcached.extraExtendedOptions:

# Increase IO threads for better performance on fast SSDs

helm install my-memcached ./memcached \
--set persistence.enabled=true \
--set persistence.size=100Gi \
--set memcached.extraExtendedOptions="ext_threads=4"

Available extstore options:

• ext_threads: Number of IO threads (default: 1)
• ext_item_size: Minimum item size for extstore
• ext_item_age: Minimum age before moving to extstore
• ext_max_sleep: Max sleep time for IO threads (microseconds)
• ext_recache_rate: Rate to recache items (items/sec)

Note: Do not manually specify ext_path or ext_wbuf_size in extraExtendedOptions - these are automatically configured from persistence settings.

Accessing Memcached

After installation, Memcached will be available at:

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

For a non-headless service:

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

Security

This chart implements several security best practices:

• Runs as non-root user (UID 11211)
• Read-only root filesystem
• Drops all capabilities
• Disabled privilege escalation
• Security context enabled by default

License

This Helm chart is open source and available under the MIT license.

Memcached License

Memcached is released under the BSD 3-clause license. See Memcached license for details.