bitnamicharts/redis-cluster repository overview

⁠Bitnami Secure Images Helm chart for Redis® Cluster

Redis® is an open source, scalable, distributed in-memory cache for applications. It can be used to store and serve data in the form of strings, hashes, lists, sets and sorted sets.

Overview of Redis® Cluster⁠

Disclaimer: Redis is a registered trademark of Redis Ltd. Any rights therein are reserved to Redis Ltd. Any use by Bitnami is for referential purposes only and does not indicate any sponsorship, endorsement, or affiliation between Redis Ltd.

⁠TL;DR

helm install my-release oci://registry-1.docker.io/bitnamicharts/redis-cluster

⁠Why use Bitnami Secure Images?

Those are hardened, minimal CVE images built and maintained by Bitnami. Bitnami Secure Images are based on the cloud-optimized, security-hardened enterprise OS Photon Linux⁠. Why choose BSI images?

• Hardened secure images of popular open source software with Near-Zero Vulnerabilities
• Vulnerability Triage & Prioritization with VEX Statements, KEV and EPSS Scores
• Compliance focus with FIPS, STIG, and air-gap options, including secure bill of materials (SBOM)
• Software supply chain provenance attestation through in-toto
• First class support for the internet’s favorite Helm charts

Each image comes with valuable security metadata. You can view the metadata in our public catalog here⁠. Note: Some data is only available with commercial subscriptions to BSI⁠.

If you are looking for our previous generation of images based on Debian Linux, please see the Bitnami Legacy registry⁠.

⁠Introduction

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

⁠Choose between Redis® Helm Chart and Redis® Cluster Helm Chart

You can choose any of the two Redis® Helm charts for deploying a Redis® cluster. While Redis® Helm Chart⁠ will deploy a master-slave cluster using Redis® Sentinel, the Redis® Cluster Helm Chart⁠ will deploy a Redis® Cluster with sharding. The main features of each chart are the following:

Redis®	Redis® Cluster
Supports multiple databases	Supports only one database. Better if you have a big dataset
Single write point (single master)	Multiple write points (multiple masters)

⁠Prerequisites

• Kubernetes 1.23+
• Helm 3.8.0+
• PV provisioner support in the underlying infrastructure

⁠Installing the Chart

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

helm install my-release oci://REGISTRY_NAME/REPOSITORY_NAME/redis-cluster

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

NOTE: if you get a timeout error waiting for the hook to complete increase the default timeout (300s) to a higher one, for example:

helm install --timeout 600s myrelease oci://REGISTRY_NAME/REPOSITORY_NAME/redis-cluster

⁠Configuration and installation details

⁠Resource requests and limits

Bitnami charts allow setting resource requests and limits for all containers inside the chart deployment. These are inside the resources value (check parameter table). Setting requests is essential for production workloads and these should be adapted to your specific use case.

To make this process easier, the chart contains the resourcesPreset values, which automatically sets the resources section according to different presets. Check these presets in the bitnami/common chart⁠. However, in production workloads using resourcesPreset is discouraged as it may not fully adapt to your specific needs. Find more information on container resource management in the official Kubernetes documentation⁠.

⁠Prometheus metrics

This chart can be integrated with Prometheus by setting metrics.enabled to true. This will deploy a sidecar container with redis_exporter⁠ in all pods and a metrics service, which can be configured under the metrics.service section. This metrics service will have the necessary annotations to be automatically scraped by Prometheus.

⁠Prometheus requirements

It is necessary to have a working installation of Prometheus or Prometheus Operator for the integration to work. Install the Bitnami Prometheus helm chart⁠ or the Bitnami Kube Prometheus helm chart⁠ to easily have a working Prometheus in your cluster.

⁠Integration with Prometheus Operator

The chart can deploy ServiceMonitor objects for integration with Prometheus Operator installations. To do so, set the value metrics.serviceMonitor.enabled=true. Ensure that the Prometheus Operator CustomResourceDefinitions are installed in the cluster or it will fail with the following error:

no matches for kind "ServiceMonitor" in version "monitoring.coreos.com/v1"

Install the Bitnami Kube Prometheus helm chart⁠ for having the necessary CRDs and the Prometheus Operator.

⁠Rolling VS Immutable tags⁠

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.

Bitnami will release a new chart updating its containers if a new version of the main container, significant changes, or critical vulnerabilities exist.

⁠Use a different Redis® version

To modify the application version used in this chart, specify a different version of the image using the image.tag parameter and/or a different repository using the image.repository parameter.

⁠Cluster topology

To successfully set the cluster up, it will need to have at least 3 master nodes. The total number of nodes is calculated like- nodes = numOfMasterNodes + numOfMasterNodes * replicas. Hence, the defaults cluster.nodes = 6 and cluster.replicas = 1 means, 3 master and 3 replica nodes will be deployed by the chart.

By default the Redis® Cluster is not accessible from outside the Kubernetes cluster, to access the Redis® Cluster from outside you have to set cluster.externalAccess.enabled=true at deployment time. It will create in the first installation only 6 LoadBalancer services, one for each Redis® node, once you have the external IPs of each service you will need to perform an upgrade passing those IPs to the cluster.externalAccess.service.loadbalancerIP array.

The replicas will be read-only replicas of the masters. By default only one service is exposed (when not using the external access mode). You will connect your client to the exposed service, regardless you need to read or write. When a write operation arrives to a replica it will redirect the client to the proper master node. For example, using redis-cli you will need to provide the -c flag for redis-cli to follow the redirection automatically.

Using the external access mode, you can connect to any of the pods and the slaves will redirect the client in the same way as explained before, but the all the IPs will be public.

In case the master crashes, one of his slaves will be promoted to master. The slots stored by the crashed master will be unavailable until the slave finish the promotion. If a master and all his slaves crash, the cluster will be down until one of them is up again. To avoid downtime, it is possible to configure the number of Redis® nodes with cluster.nodes and the number of replicas that will be assigned to each master with cluster.replicas. For example:

• cluster.nodes=9 ( 3 master plus 2 replicas for each master)
• cluster.replicas=2

Providing the values above, the cluster will have 3 masters and, each master, will have 2 replicas.

⁠Adding a new node to the cluster

There is a job that will be executed using a post-upgrade hook that will allow you to add a new node. To use it, you should provide some parameters to the upgrade:

• Pass as password the password used in the installation time. If you did not provide a password follow the instructions from the NOTES.txt to get the generated password.
• Set the desired number of nodes at cluster.nodes.
• Set the number of current nodes at cluster.update.currentNumberOfNodes.
• Set to true cluster.update.addNodes.

The following will be an example to add one more node:

helm upgrade --timeout 600s <release> --set "password=${REDIS_PASSWORD},cluster.nodes=7,cluster.update.addNodes=true,cluster.update.currentNumberOfNodes=6" oci://REGISTRY_NAME/REPOSITORY_NAME/redis-cluster

Where REDIS_PASSWORD is the password obtained with the command that appears after the first installation of the Helm Chart. The cluster will continue up while restarting pods one by one as the quorum is not lost.

⁠External Access

If you are using external access, to add a new node you will need to perform two upgrades. First upgrade the release to add a new Redis® node and to get a LoadBalancerIP service. For example:

helm upgrade <release> --set "password=${REDIS_PASSWORD},cluster.externalAccess.enabled=true,cluster.externalAccess.service.type=LoadBalancer,cluster.externalAccess.service.loadBalancerIP[0]=<loadBalancerip-0>,cluster.externalAccess.service.loadBalancerIP[1]=<loadbalanacerip-1>,cluster.externalAccess.service.loadBalancerIP[2]=<loadbalancerip-2>,cluster.externalAccess.service.loadBalancerIP[3]=<loadbalancerip-3>,cluster.externalAccess.service.loadBalancerIP[4]=<loadbalancerip-4>,cluster.externalAccess.service.loadBalancerIP[5]=<loadbalancerip-5>,cluster.externalAccess.service.loadBalancerIP[6]=,cluster.nodes=7,cluster.init=false" oci://REGISTRY_NAME/REPOSITORY_NAME/redis-cluster

As we want to add a new node, we are setting cluster.nodes=7 and we leave empty the LoadBalancerIP for the new node, so the cluster will provide the correct one. REDIS_PASSWORD is the password obtained with the command that appears after the first installation of the Helm Chart. At this point, you will have a new Redis® Pod that will remain in crashLoopBackOff state until we provide the LoadBalancerIP for the new service. Now, wait until the cluster provides the new LoadBalancerIP for the new service and perform the second upgrade:

helm upgrade <release> --set "password=${REDIS_PASSWORD},cluster.externalAccess.enabled=true,cluster.externalAccess.service.type=LoadBalancer,cluster.externalAccess.service.loadBalancerIP[0]=<loadbalancerip-0>,cluster.externalAccess.service.loadBalancerIP[1]=<loadbalancerip-1>,cluster.externalAccess.service.loadBalancerIP[2]=<loadbalancerip-2>,cluster.externalAccess.service.loadBalancerIP[3]=<loadbalancerip-3>,cluster.externalAccess.service.loadBalancerIP[4]=<loadbalancerip-4>,cluster.externalAccess.service.loadBalancerIP[5]=<loadbalancerip-5>,cluster.externalAccess.service.loadBalancerIP[6]=<loadbalancerip-6>,cluster.nodes=7,cluster.init=false,cluster.update.addNodes=true,cluster.update.newExternalIPs[0]=<load-balancerip-6>" oci://REGISTRY_NAME/REPOSITORY_NAME/redis-cluster

Note we are providing the new IPs at cluster.update.newExternalIPs, the flag cluster.update.addNodes=true to enable the creation of the Job that adds a new node and now we are setting the LoadBalancerIP of the new service instead of leave it empty.

⁠Scale down the cluster

To scale down the Redis® Cluster, follow these steps:

First perform a normal upgrade setting the cluster.nodes value to the desired number of nodes. It should not be less than 6 and the difference between current number of nodes and the desired should be less or equal to cluster.replicas to avoid removing master node an its slaves at the same time. Also it is needed to provide the password using the password. For example, having more than 6 nodes, to scale down the cluster to 6 nodes:

helm upgrade --timeout 600s <release> --set "password=${REDIS_PASSWORD},cluster.nodes=6" .

The cluster will continue working during the update as long as the quorum is not lost.

Once all the nodes are ready, get the list of nodes in the cluster using the CLUSTER NODES command. You will see references to the ones that were removed. Write down the node IDs of the nodes that show fail. In the following example the cluster scaled down from 7 to 6 nodes.

redis-cli -a $REDIS_PASSWORD CLUSTER NODES

...
b23bcffa1fd64368d445c1d9bd9aeb92641105f7 10.0.0.70:6379@16379 slave,fail - 1645633139060 0 0 connected
...

In each cluster node, execute the following command. Replace the NODE_ID placeholder.

redis-cli -a $REDIS_PASSWORD CLUSTER FORGET NODE_ID

In the previous example the commands would look like this in each cluster node:

redis-cli -a $REDIS_PASSWORD CLUSTER FORGET b23bcffa1fd64368d445c1d9bd9aeb92641105f7

⁠Using password file

To use a password file for Redis® you need to create a secret containing the password.

And then deploy the Helm Chart using the secret name as parameter:

usePassword=true
usePasswordFile=true
existingSecret=redis-password-secret
metrics.enabled=true

⁠Securing traffic using TLS

TLS support can be enabled in the chart by specifying the tls. parameters while creating a release. The following parameters should be configured to properly enable the TLS support in the cluster:

• tls.enabled: Enable TLS support. Defaults to false
• tls.existingSecret: Name of the secret that contains the certificates. No defaults.
• tls.certFilename: Certificate filename. No defaults.
• tls.certKeyFilename: Certificate key filename. No defaults.
• tls.certCAFilename: CA Certificate filename. No defaults.

For example:

First, create the secret with the certificates files:

kubectl create secret generic certificates-tls-secret --from-file=./cert.pem --from-file=./cert.key --from-file=./ca.pem

Then, use the following parameters:

tls.enabled="true"
tls.existingSecret="certificates-tls-secret"
tls.certFilename="cert.pem"
tls.certKeyFilename="cert.key"
tls.certCAFilename="ca.pem"

⁠Sidecars and Init Containers

If you have a need for additional containers to run within the same pod as Redis® (e.g. an additional metrics or logging exporter), you can do so via the sidecars config parameter. Simply define your container according to the Kubernetes container spec.

sidecars:
  - name: your-image-name
    image: your-image
    imagePullPolicy: Always
    ports:
      - name: portname
       containerPort: 1234

Similarly, you can add extra init containers using the initContainers parameter.

initContainers:
  - name: your-image-name
    image: your-image
    imagePullPolicy: Always
    ports:
      - name: portname
        containerPort: 1234

⁠Adding extra environment variables

In case you want to add extra environment variables (useful for advanced operations like custom init scripts), you can use the extraEnvVars property.

extraEnvVars:
  - name: REDIS_WHATEVER
    value: value

Alternatively, you can use a ConfigMap or a Secret with the environment variables. To do so, use the extraEnvVarsCM or the extraEnvVarsSecret values.

⁠Metrics

The chart optionally can start a metrics exporter for prometheus⁠. The metrics endpoint (port 9121) is exposed in the service. Metrics can be scraped from within the cluster using something similar as the described in the example Prometheus scrape configuration⁠. If metrics are to be scraped from outside the cluster, the Kubernetes API proxy can be utilized to access the endpoint.

⁠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
    - -c
    - |-
      sysctl -w net.core.somaxconn=10000
      echo never > /host-sys/kernel/mm/transparent_hugepage/enabled

Alternatively, for Kubernetes 1.12+ you can set podSecurityContext.sysctls which will configure sysctls for master and slave pods. Example:

podSecurityContext:
  sysctls:
  - name: net.core.somaxconn
    value: "10000"

Note that this will not disable transparent huge tables.

⁠Helm Upgrade

By default cluster.init will be set to true in order to initialize the Redis® Cluster in the first installation. If for testing purposes you only want to deploy or upgrade the nodes but avoiding the creation of the cluster you can set cluster.init to false.

⁠Backup and restore

To back up and restore Redis Cluster Helm chart deployments on Kubernetes, you need to back up the persistent volumes from the source deployment and attach them to a new deployment using Velero⁠, a Kubernetes backup/restore tool.

These are the steps you will usually follow to back up and restore your Redis Cluster database cluster data:

• Install Velero on the source and destination clusters.
• Use Velero to back up the PersistentVolumes (PVs) used by the deployment on the source cluster.
• Use Velero to restore the backed-up PVs on the destination cluster.
• Create a new deployment on the destination cluster with the same chart, deployment name, credentials and other parameters as the original. This new deployment will use the restored PVs and hence the original data.

Refer to our detailed tutorial on backing up and restoring Redis Cluster deployments on Kubernetes⁠ for more information.

⁠NetworkPolicy

To enable network policy for Redis®, install a networking plugin that implements the Kubernetes NetworkPolicy spec⁠, and set networkPolicy.enabled to true.

For Kubernetes v1.5 & v1.6, you must also turn on NetworkPolicy by setting the DefaultDeny namespace annotation. Note: this will enforce policy for all pods in the namespace:

kubectl annotate namespace default "net.beta.kubernetes.io/network-policy={\"ingress\":{\"isolation\":\"DefaultDeny\"}}"

With NetworkPolicy enabled, only pods with the generated client label will be able to connect to Redis®. This label will be displayed in the output after a successful install.

With networkPolicy.ingressNSMatchLabels pods from other namespaces can connect to redis. Set networkPolicy.ingressNSPodMatchLabels to match pod labels in matched namespace. For example, for a namespace labeled redis=external and pods in that namespace labeled redis-client=true the fields should be set:

networkPolicy:
  enabled: true
  ingressNSMatchLabels:
    redis: external
  ingressNSPodMatchLabels:
    redis-client: true

⁠Setting Pod's affinity

This chart allows you to set your custom affinity using the XXX.affinity paremeter(s). Find more information about Pod's affinity in the kubernetes documentation⁠.

As an alternative, you can use of the preset configurations for pod affinity, pod anti-affinity, and node affinity available at the bitnami/common⁠ chart. To do so, set the XXX.podAffinityPreset, XXX.podAntiAffinityPreset, or XXX.nodeAffinityPreset parameters.

⁠Persistence

By default, the chart mounts a Persistent Volume⁠ at the /bitnami path. The volume is created using dynamic volume provisioning.

If persistence is disabled, an emptyDir volume is used. This is only recommended for testing environments because the required information included in the nodes.conf file is missing. This file contains the relationship between the nodes and the cluster. For example, if any node is down or faulty, when it starts again, it is a self-proclaimed master and also acts as an independent node outside the main cluster as it doesn't have the necessary information to connect to it.

To reconnect the failed node, run the following:

See nodes.sh

$ cat /bitnami/redis/data/nodes.sh
declare -A host_2_ip_array=([redis-node-0]="192.168.192.6" [redis-node-1]="192.168.192.2" [redis-node-2]="192.168.192.4" [redis-node-3]="192.168.192.5" [redis-node-4]="192.168.192.3" [redis-node-5]="192.168.192.7" )

Run redis-cli and run CLUSTER MEET⁠ to any other node in the cluster. Now

Note: the README for this chart is longer than the DockerHub length limit of 25000, so it has been trimmed. The full README can be found at https://github.com/bitnami/charts/blob/main/bitnami/redis-cluster/README.md⁠