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 3 pods total:

• one pod containing a redis master and sentinel container (optional prometheus metrics exporter sidecar available)
• two pods each containing a redis slave and sentinel containers (optional prometheus metrics exporter sidecars available)

Introduction

This chart bootstraps a Redis highly available master/slave statefulset in a Kubernetes cluster using the Helm package manager.

Prerequisites

• Kubernetes 1.8+ with Beta APIs enabled
• PV provisioner support in the underlying infrastructure

Upgrading the Chart

Please note that there have been a number of changes simplifying the redis management strategy (for better failover and elections) in the 3.x version of this chart. These changes allow the use of official redis images that do not require special RBAC or ServiceAccount roles. As a result when upgrading from version >=2.0.1 to >=3.0.0 of this chart, Role, RoleBinding, and ServiceAccount resources should be deleted manually.

Upgrading the chart from 3.x to 4.x

Starting from version 4.x HAProxy sidecar prometheus-exporter removed and replaced by by the embedded HAProxy metrics endpoint, as a result when upgrading from version 3.x to 4.x section haproxy.exporter should be removed and the haproxy.metrics need to be configured for fit your needs.

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 along with 2 redis slave pods each containing their own sentinel sidecars. 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.

Configuration

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

Parameter	Description	Default
image	Redis image	redis
tag	Redis tag	5.0.6-alpine
replicas	Number of redis master/slave pods	3
serviceAccount.create	Specifies whether a ServiceAccount should be created	true
serviceAccount.name	The name of the ServiceAccount to create	Generated using the redis-ha.fullname template
rbac.create	Create and use RBAC resources	true
redis.port	Port to access the redis service	6379
redis.masterGroupName	Redis convention for naming the cluster group: must match ^[\\w-\\.]+$ and can be templated	mymaster
redis.config	Any valid redis config options in this section will be applied to each server (see below)	see values.yaml
redis.customConfig	Allows for custom redis.conf files to be applied. If this is used then redis.config is ignored	``
redis.resources	CPU/Memory for master/slave nodes resource requests/limits	{}
sentinel.port	Port to access the sentinel service	26379
sentinel.quorum	Minimum number of servers necessary to maintain quorum	2
sentinel.config	Valid sentinel config options in this section will be applied as config options to each sentinel (see below)	see values.yaml
sentinel.customConfig	Allows for custom sentinel.conf files to be applied. If this is used then sentinel.config is ignored	``
sentinel.resources	CPU/Memory for sentinel node resource requests/limits	{}
init.resources	CPU/Memory for init Container node resource requests/limits	{}
auth	Enables or disables redis AUTH (Requires redisPassword to be set)	false
redisPassword	A password that configures a requirepass and masterauth in the conf parameters (Requires auth: enabled)	``
authKey	The key holding the redis password in an existing secret.	auth
existingSecret	An existing secret containing a key defined by authKey that configures requirepass and masterauth in the conf parameters (Requires auth: enabled, cannot be used in conjunction with .Values.redisPassword)	``
nodeSelector	Node labels for pod assignment	{}
tolerations	Toleration labels for pod assignment	[]
hardAntiAffinity	Whether the Redis server pods should be forced to run on separate nodes.	true
additionalAffinities	Additional affinities to add to the Redis server pods.	{}
securityContext	Security context to be added to the Redis server pods.	{runAsUser: 1000, fsGroup: 1000, runAsNonRoot: true}
affinity	Override all other affinity settings with a string.	""
exporter.enabled	If true, the prometheus exporter sidecar is enabled	false
exporter.image	Exporter image	oliver006/redis_exporter
exporter.tag	Exporter tag	v0.31.0
exporter.port	Exporter port	9121
exporter.annotations	Prometheus scrape annotations	{prometheus.io/path: /metrics, prometheus.io/port: "9121", prometheus.io/scrape: "true"}
exporter.extraArgs	Additional args for the exporter	{}
exporter.serviceMonitor.enabled	Use servicemonitor from prometheus operator	false
exporter.serviceMonitor.namespace	Namespace the service monitor is created in	default
exporter.serviceMonitor.interval	Scrape interval, If not set, the Prometheus default scrape interval is used	nil
exporter.serviceMonitor.telemetryPath	Path to redis-exporter telemetry-path	/metrics
exporter.serviceMonitor.labels	Labels for the servicemonitor passed to Prometheus Operator	{}
exporter.serviceMonitor.timeout	How long until a scrape request times out. If not set, the Prometheus default scape timeout is used	nil
haproxy.enabled	Enabled HAProxy LoadBalancing/Proxy	false
haproxy.replicas	Number of HAProxy instances	3
haproxy.image.repository	HAProxy Image Repository	haproxy
haproxy.image.tag	HAProxy Image Tag	2.0.1
haproxy.image.pullPolicy	HAProxy Image PullPolicy	IfNotPresent
haproxy.annotations	HAProxy template annotations	{}
haproxy.customConfig	Allows for custom config-haproxy.cfg file to be applied. If this is used then default config will be overwriten	``
haproxy.extraConfig	Allows to place any additional configuration section to add to the default config-haproxy.cfg	``
haproxy.resources	HAProxy resources	{}
haproxy.service.type	HAProxy service type "ClusterIP", "LoadBalancer" or "NodePort"	ClusterIP
haproxy.service.nodePort	HAProxy service nodePort value (haproxy.service.type must be NodePort)	not set
haproxy.service.annotations	HAProxy service annotations	{}
haproxy.hapreadport.enable	Enable a read only port for redis slaves	false
haproxy.hapreadport.port	Haproxy port for read only redis slaves	6380
haproxy.metrics.enabled	HAProxy enable prometheus metric scraping	false
haproxy.metrics.port	HAProxy prometheus metrics scraping port	9101
haproxy.metrics.portName	HAProxy metrics scraping port name	exporter-port
haproxy.metrics.scrapePath	HAProxy prometheus metrics scraping port	/metrics
haproxy.metrics.serviceMonitor.enabled	Use servicemonitor from prometheus operator for HAProxy metrics	false
haproxy.metrics.serviceMonitor.namespace	Namespace the service monitor for HAProxy metrics is created in	default
haproxy.metrics.serviceMonitor.interval	Scrape interval, If not set, the Prometheus default scrape interval is used	nil
haproxy.metrics.serviceMonitor.telemetryPath	Path to HAProxy metrics telemetry-path	/metrics
haproxy.metrics.serviceMonitor.labels	Labels for the HAProxy metrics servicemonitor passed to Prometheus Operator	{}
haproxy.metrics.serviceMonitor.timeout	How long until a scrape request times out. If not set, the Prometheus default scape timeout is used	nil
haproxy.init.resources	Extra init resources	{}
haproxy.timeout.connect	haproxy.cfg timeout connect setting	4s
haproxy.timeout.server	haproxy.cfg timeout server setting	30s
haproxy.timeout.client	haproxy.cfg timeout client setting	30s
haproxy.priorityClassName	priorityClassName for haproxy deployment	not set
haproxy.securityContext	Security context to be added to the HAProxy deployment.	{runAsUser: 1000, fsGroup: 1000, runAsNonRoot: true}
haproxy.hardAntiAffinity	Whether the haproxy pods should be forced to run on separate nodes.	true
haproxy.affinity	Override all other haproxy affinity settings with a string.	""
haproxy.additionalAffinities	Additional affinities to add to the haproxy server pods.	{}
podDisruptionBudget	Pod Disruption Budget rules	{}
priorityClassName	priorityClassName for redis-ha-statefulset	not set
hostPath.path	Use this path on the host for data storage	not set
hostPath.chown	Run an init-container as root to set ownership on the hostPath	true
sysctlImage.enabled	Enable an init container to modify Kernel settings	false
sysctlImage.command	sysctlImage command to execute	[]
sysctlImage.registry	sysctlImage Init container registry	docker.io
sysctlImage.repository	sysctlImage Init container name	busybox
sysctlImage.tag	sysctlImage Init container tag	1.31.1
sysctlImage.pullPolicy	sysctlImage Init container pull policy	Always
sysctlImage.mountHostSys	Mount the host /sys folder to /host-sys	false
schedulerName	Alternate scheduler name	nil

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

$ helm install \
  --set image=redis \
  --set tag=5.0.5-alpine \
    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

Custom Redis and Sentinel config options

This chart allows for most redis or sentinel config options to be passed as a key value pair through the values.yaml under redis.config and sentinel.config. See links below for all available options.

Example redis.conf Example sentinel.conf

For example repl-timeout 60 would be added to the redis.config section of the values.yaml as:

    repl-timeout: "60"

Note:

1. Some config options should be renamed by redis version，e.g.:

   # In redis 5.x，see https://raw.githubusercontent.com/antirez/redis/5.0/redis.conf
   min-replicas-to-write: 1
   min-replicas-max-lag: 5
   
   # In redis 4.x and redis 3.x，see https://raw.githubusercontent.com/antirez/redis/4.0/redis.conf and https://raw.githubusercontent.com/antirez/redis/3.0/redis.conf
   min-slaves-to-write 1
   min-slaves-max-lag 5
   

Sentinel options supported must be in the the sentinel <option> <master-group-name> <value> format. For example, sentinel down-after-milliseconds 30000 would be added to the sentinel.config section of the values.yaml as:

    down-after-milliseconds: 30000

If more control is needed from either the redis or sentinel config then an entire config can be defined under redis.customConfig or sentinel.customConfig. Please note that these values will override any configuration options under their respective section. For example, if you define sentinel.customConfig then the sentinel.config is ignored.

Host Kernel Settings

Redis may require some changes in the kernel of the host machine to work as expected, in particular increasing the somaxconn value and disabling transparent huge pages. To do so, you can set up a privileged initContainer with the sysctlImage config values, for example:

sysctlImage:
  enabled: true
  mountHostSys: true
  command:
    - /bin/sh
    - -xc
    - |-
      sysctl -w net.core.somaxconn=10000
      echo never > /host-sys/kernel/mm/transparent_hugepage/enabled

HAProxy startup

When HAProxy is enabled, it will attempt to connect to each announce-service of each redis replica instance in its init container before starting. It will fail if announce-service IP is not available fast enough (10 seconds max by announce-service). A such case could happen if the orchestator is pending the nomination of redis pods. Risk is limited because announce-service is using publishNotReadyAddresses: true, although, in such case, HAProxy pod will be rescheduled afterward by the orchestrator.