Redis

Redis is an advanced key-value cache and store. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets, sorted sets, bitmaps and hyperloglogs.

TL;DR;

$ helm install stable/redis-ha

By default this chart install one master pod containing redis master container and sentinel container, 2 sentinels and 1 redis slave.

Introduction

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

Prerequisites

• Kubernetes 1.5+ with Beta APIs enabled
• PV provisioner support in the underlying infrastructure

Installing the Chart

To install the chart

$ helm install stable/redis-ha

The command deploys Redis on the Kubernetes cluster in the default configuration. By default this chart install one master pod containing redis master container and sentinel container, 2 sentinels and 1 redis slave. The configuration section lists the parameters that can be configured during installation.

Tip: List all releases using helm list

Uninstalling the Chart

To uninstall/delete the deployment:

$ helm delete <chart-name>

The command removes all the Kubernetes components associated with the chart and deletes the release.

Appliance mode

This chart can be used to launch Redis in a black box appliance mode that you can think of like a managed service. To run as an appliance, change the service type for the master and slave LBs to enable local access from within the K8S cluster.

To launch in VPC-only appliance mode, set appliance.serviceType to "LoadBalancer". If using appliance mode in Google Cloud, set appliance.annotations to: cloud.google.com/load-balancer-type:Internal

$ helm install \
  --set="servers.annotations.cloud\.google\.com/load-balancer-type=Internal,servers.serviceType=LoadBalancer" \
    stable/redis-ha

Configuration

The following tables lists the configurable parameters of the Redis chart and their default values.

Parameter	Description	Default
redis_image	Redis image	quay.io/smile/redis:4.0.6r2
resources.master	CPU/Memory for master nodes resource requests/limits	Memory: 200Mi, CPU: 100m
resources.slave	CPU/Memory for slave nodes resource requests/limits	Memory: 200Mi, CPU: 100m
resources.sentinel	CPU/Memory for sentinel node resource requests/limits	Memory: 200Mi, CPU: 100m
replicas.servers	Number of redis master/slave pods	3
replicas.sentinels	Number of sentinel pods	3
nodeSelector	Node labels for pod assignment	{}
tolerations	Toleration labels for pod assignment	[]
servers.serviceType	Set to "LoadBalancer" to enable access from the VPC	ClusterIP
servers.annotations	See Appliance mode	``

Specify each parameter using the --set key=value[,key=value] argument to helm install. For example,

$ helm install \
  --set redis_image=quay.io/smile/redis:4.0.6r2 \
    stable/redis-ha

The above command sets the Redis server within default namespace.

Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example,

$ helm install -f values.yaml stable/redis-ha

Tip: You can use the default values.yaml

Internals

The customized Redis server image determines whether the pod that executes it will be a Redis Sentinel, Master, or Slave and launches the appropriate service. This Helm chart signals Sentinel status with environment variables. If not set, the newly launched pod will query K8S for an active master. If none exists, it uses a deterministic means of sensing whether it should launch as master then writes "master" or "slave" to the label called redis-role as appropriate. It's this label that determines which LB a pod can be seen through.

The redis-role=master pod is the key for the cluster to get started. Sentinels will wait for it to appear in the LB before they finish launching. All other pods wait for the Sentinels to ID the master. Running Pods also set the labels podIP and runID. runID is the first few characters of the unique run_id value generated by each Redis sever.

During normal operation, there should be only one redis-role=master pod. If it fails, the Sentinels will nominate a new master and change all the redis-role values appropriately.

To see the pod roles, run the following:

$ kubectl get pods -L redis-role