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176 lines
14 KiB
Markdown
176 lines
14 KiB
Markdown
# Memcached
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> [Memcached](https://memcached.org/) is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering.
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## TL;DR;
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```console
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$ helm repo add bitnami https://charts.bitnami.com/bitnami
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$ helm install my-release bitnami/memcached
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```
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## Introduction
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This chart bootstraps a [Memcached](https://github.com/bitnami/bitnami-docker-memcached) deployment on a [Kubernetes](http://kubernetes.io) cluster using the [Helm](https://helm.sh) package manager.
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Bitnami charts can be used with [Kubeapps](https://kubeapps.com/) for deployment and management of Helm Charts in clusters. This Helm chart has been tested on top of [Bitnami Kubernetes Production Runtime](https://kubeprod.io/) (BKPR). Deploy BKPR to get automated TLS certificates, logging and monitoring for your applications.
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## Prerequisites
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- Kubernetes 1.12+
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- Helm 2.11+ or Helm 3.0-beta3+
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## Installing the Chart
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To install the chart with the release name `my-release`:
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```console
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$ helm repo add bitnami https://charts.bitnami.com/bitnami
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$ helm install my-release bitnami/memcached
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```
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These commands deploy Memcached on the Kubernetes cluster in the default configuration. The [Parameters](#parameters) section lists the parameters that can be configured during installation.
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> **Tip**: List all releases using `helm list`
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## Uninstalling the Chart
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To uninstall/delete the `my-release` deployment:
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```console
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$ helm delete my-release
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```
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The command removes all the Kubernetes components associated with the chart and deletes the release.
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## Parameters
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The following tables lists the configurable parameters of the Memcached chart and their default values.
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| Parameter | Description | Default |
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| ----------------------------- | ------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------ |
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| `global.imageRegistry` | Global Docker image registry | `nil` |
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| `global.imagePullSecrets` | Global Docker registry secret names as an array | `[]` (does not add image pull secrets to deployed pods) |
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| `image.registry` | Memcached image registry | `docker.io` |
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| `image.repository` | Memcached Image name | `bitnami/memcached` |
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| `image.tag` | Memcached Image tag | `{TAG_NAME}` |
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| `image.pullPolicy` | Memcached image pull policy | `IfNotPresent` |
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| `image.pullSecrets` | Specify docker-registry secret names as an array | `[]` (does not add image pull secrets to deployed pods) |
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| `nameOverride` | String to partially override memcached.fullname template with a string (will prepend the release name) | `nil` |
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| `fullnameOverride` | String to fully override memcached.fullname template with a string | `nil` |
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| `clusterDomain` | Kubernetes cluster domain | `cluster.local` |
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|`replicas` | Number of containers | `1` |
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|`extraEnv` | Additional env vars to pass | `{}` |
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|`arguments` | Arguments to pass | `["/run.sh"]` |
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| `memcachedUsername` | Memcached admin user | `nil` |
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| `memcachedPassword` | Memcached admin password | `nil` |
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| `service.type` | Kubernetes service type for Memcached | `ClusterIP` |
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| `service.port` | Memcached service port | `11211` |
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| `service.clusterIP` | Specific cluster IP when service type is cluster IP. Use `None` for headless service | `nil` |
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| `service.nodePort` | Kubernetes Service nodePort | `nil` |
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| `service.loadBalancerIP` | `loadBalancerIP` if service type is `LoadBalancer` | `nil` |
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| `service.annotations` | Additional annotations for Memcached service | `{}` |
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| `resources.requests` | CPU/Memory resource requests | `{memory: "256Mi", cpu: "250m"}` |
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| `resources.limits` | CPU/Memory resource limits | `{}` |
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| `persistence.enabled` | Enable persistence using PVC | `true` |
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| `persistence.storageClass` | PVC Storage Class for Jenkins volume | `nil` (uses alpha storage class annotation) |
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| `persistence.accessMode` | PVC Access Mode for Jenkins volume | `ReadWriteOnce` |
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| `persistence.size` | PVC Storage Request for Jenkins volume | `8Gi` |
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| `securityContext.enabled` | Enable security context | `true` |
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| `securityContext.fsGroup` | Group ID for the container | `1001` |
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| `securityContext.runAsUser` | User ID for the container | `1001` |
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| `securityContext.readOnlyRootFilesystem` | Enable read-only filesystem | `false` |
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| `podAnnotations` | Pod annotations | `{}` |
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| `affinity` | Map of node/pod affinities | `{}` (The value is evaluated as a template) |
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| `nodeSelector` | Node labels for pod assignment | `{}` (The value is evaluated as a template) |
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| `tolerations` | Tolerations for pod assignment | `[]` (The value is evaluated as a template) |
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| `metrics.enabled` | Start a side-car prometheus exporter | `false` |
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| `metrics.image.registry` | Memcached exporter image registry | `docker.io` |
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| `metrics.image.repository` | Memcached exporter image name | `bitnami/memcached-exporter` |
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| `metrics.image.tag` | Memcached exporter image tag | `{TAG_NAME}` |
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| `metrics.image.pullPolicy` | Image pull policy | `IfNotPresent` |
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| `metrics.image.pullSecrets` | Specify docker-registry secret names as an array | `[]` (does not add image pull secrets to deployed pods) |
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| `metrics.podAnnotations` | Additional annotations for Metrics exporter | `{prometheus.io/scrape: "true", prometheus.io/port: "9150"}` |
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| `metrics.resources` | Exporter resource requests/limit | `{}` |
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| `metrics.service.type` | Kubernetes service type for Prometheus metrics | `ClusterIP` |
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| `metrics.service.port` | Prometheus metrics service port | `9150` |
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| `metrics.service.annotations` | Prometheus exporter svc annotations | `{prometheus.io/scrape: "true", prometheus.io/port: "9150"}` |
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The above parameters map to the env variables defined in [bitnami/memcached](http://github.com/bitnami/bitnami-docker-memcached). For more information please refer to the [bitnami/memcached](http://github.com/bitnami/bitnami-docker-memcached) image documentation.
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Specify each parameter using the `--set key=value[,key=value]` argument to `helm install`. For example,
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```console
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$ helm install my-release --set memcachedUsername=user,memcachedPassword=password bitnami/memcached
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```
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The above command sets the Memcached admin account username and password to `user` and `password` respectively.
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Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example,
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```console
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$ helm install my-release -f values.yaml bitnami/memcached
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```
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> **Tip**: You can use the default [values.yaml](values.yaml)
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## Configuration and installation details
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### [Rolling VS Immutable tags](https://docs.bitnami.com/containers/how-to/understand-rolling-tags-containers/)
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It is strongly recommended to use immutable tags in a production environment. This ensures your deployment does not change automatically if the same tag is updated with a different image.
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Bitnami will release a new chart updating its containers if a new version of the main container, significant changes, or critical vulnerabilities exist.
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### Production configuration
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This chart includes a `values-production.yaml` file where you can find some parameters oriented to production configuration in comparison to the regular `values.yaml`. You can use this file instead of the default one.
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- Start a side-car prometheus exporter:
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```diff
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- metrics.enabled: false
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+ metrics.enabled: true
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```
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- Enable read-only filesystem:
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```diff
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- securityContext.readOnlyRootFilesystem=false
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+ securityContext.readOnlyRootFilesystem=true
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```
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## Persistence
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The [Bitnami Memcached](https://github.com/bitnami/bitnami-docker-memcached) image stores the cache-state at the `/cache-state` path of the container if enabled.
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Persistent Volume Claims are used to keep the data across deployments. This is known to work in GCE, AWS, and minikube.
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See the [Parameters](#parameters) section to configure the PVC or to disable persistence.
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## Notable changes
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### 4.0.0
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Backwards compatibility is not guaranteed unless you modify the labels used on the chart's deployments.
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Use the workaround below to upgrade from versions previous to 4.0.0. The following example assumes that the release name is memcached:
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```console
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$ kubectl delete deployment memcached --cascade=false
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$ helm upgrade memcached bitnami/memcached
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```
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### 3.0.0
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This release uses the new bash based `bitnami/memcached` container which uses bash scripts for the start up logic of the container and is smaller in size.
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## Upgrading
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### To 1.0.0
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Backwards compatibility is not guaranteed unless you modify the labels used on the chart's deployments.
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Use the workaround below to upgrade from versions previous to 1.0.0. The following example assumes that the release name is memcached:
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```console
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$ kubectl patch deployment memcached --type=json -p='[{"op": "remove", "path": "/spec/selector/matchLabels/chart"}]'
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```
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