redis-operator

Redis Operator creates/configures/manages redis-failovers atop Kubernetes.

Requirements

Redis Operator is meant to be run on Kubernetes 1.19+. All dependencies have been vendored, so there's no need to any additional download.

Operator deployment on kubernetes

In order to create Redis failovers inside a Kubernetes cluster, the operator has to be deployed. It can be done with deployment or with the provided Helm chart.

Using the Helm chart

From the root folder of the project, execute the following:

helm repo add redis-operator https://spotahome.github.io/redis-operator
helm repo update
helm install redis-operator redis-operator/redis-operator

Update helm chart

Helm chart only manage the creation of CRD in the first install. In order to update the CRD you will need to apply directly.

kubectl apply -f https://raw.githubusercontent.com/spotahome/redis-operator/master/manifests/databases.spotahome.com_redisfailovers.yaml

helm upgrade redis-operator redis-operator/redis-operator

Using kubectl

To create the operator, you can directly create it with kubectl:

kubectl apply -f https://raw.githubusercontent.com/spotahome/redis-operator/master/manifests/databases.spotahome.com_redisfailovers.yaml
kubectl apply -f https://raw.githubusercontent.com/spotahome/redis-operator/master/example/operator/all-redis-operator-resources.yaml

This will create a deployment named redisoperator.

Usage

Once the operator is deployed inside a Kubernetes cluster, a new API will be accesible, so you'll be able to create, update and delete redisfailovers.

In order to deploy a new redis-failover a specification has to be created:

kubectl create -f https://raw.githubusercontent.com/spotahome/redis-operator/master/example/redisfailover/basic.yaml

This redis-failover will be managed by the operator, resulting in the following elements created inside Kubernetes:

• rfr-<NAME>: Redis configmap
• rfr-<NAME>: Redis statefulset
• rfr-<NAME>: Redis service (if redis-exporter is enabled)
• rfs-<NAME>: Sentinel configmap
• rfs-<NAME>: Sentinel deployment
• rfs-<NAME>: Sentinel service

NOTE: NAME is the named provided when creating the RedisFailover. IMPORTANT: the name of the redis-failover to be created cannot be longer that 48 characters, due to prepend of redis/sentinel identification and statefulset limitation.

Persistence

The operator has the ability of add persistence to Redis data. By default an emptyDir will be used, so the data is not saved.

In order to have persistence, a PersistentVolumeClaim usage is allowed. The full PVC definition has to be added to the Redis Failover Spec under the Storage section.

IMPORTANT: By default, the persistent volume claims will be deleted when the Redis Failover is. If this is not the expected usage, a keepAfterDeletion flag can be added under the storage section of Redis. An example is given.

NodeAffinity and Tolerations

You can use NodeAffinity and Tolerations to deploy Pods to isolated groups of Nodes. Examples are given for node affinity, pod anti affinity and tolerations.

Topology Spread Contraints

You can use the topologySpreadContraints to ensure the pods of a type(redis or sentinel) are evenly distributed across zones/nodes. Examples are for using topology spread constraints. Further document on how topologySpreadConstraints work could be found here.

Custom configurations

It is possible to configure both Redis and Sentinel. This is done with the customConfig option inside their spec. It is a list of configurations and their values. Example are given in the custom config example file.

In order to have the ability of this configurations to be changed "on the fly", without the need of reload the redis/sentinel processes, the operator will apply them with calls to the redises/sentinels, using config set or sentinel set mymaster respectively. Because of this, no changes on the configmaps will appear regarding this custom configurations and the entries of customConfig from Redis spec will not be written on redis.conf file. To verify the actual Redis configuration use redis-cli CONFIG GET *.

Important: in the Sentinel options, there are some "conversions" to be made:

• Configuration on the sentinel.conf: sentinel down-after-milliseconds mymaster 2000
• Configuration on the configOptions: down-after-milliseconds 2000

Important 2: do NOT change the options used for control the redis/sentinel such as port, bind, dir, etc.

Custom shutdown script

By default, a custom shutdown file is given. This file makes redis to SAVE it's data, and in the case that redis is master, it'll call sentinel to ask for a failover.

This behavior is configurable, creating a configmap and indicating to use it. An example about how to use this option can be found on the shutdown example file.

Important: the configmap has to be in the same namespace. The configmap has to have a shutdown.sh data, containing the script.

Custom SecurityContext

By default Kubernetes will run containers as the user specified in the Dockerfile (or the root user if not specified), this is not always desirable. If you need the containers to run as a specific user (or provide any other PodSecurityContext options) then you can specify a custom securityContext in the redisfailover object. See the SecurityContext example file for an example. Keys available under securityContext are detailed here

Custom containerSecurityContext at container level

By default Kubernetes will run containers with default docker capabilities for exemple, this is not always desirable. If you need the containers to run with specific capabilities or with read only root file system (or provide any other securityContext options) then you can specify a custom containerSecurityContext in the redisfailover object. See the ContainerSecurityContext example file for an example. Keys available under containerSecurityContext are detailed here

Custom command

By default, redis and sentinel will be called with the basic command, giving the configuration file:

• Redis: redis-server /redis/redis.conf
• Sentinel: redis-server /redis/sentinel.conf --sentinel

If necessary, this command can be changed with the command option inside redis/sentinel spec. An example can be found in the custom command example file.

Custom Priority Class

In order to use a custom Kubernetes Priority Class for Redis and/or Sentinel pods, you can set the priorityClassName in the redis/sentinel spec, this attribute has no default and depends on the specific cluster configuration. Note: the operator doesn't create the referenced Priority Class resource.

Custom Service Account

In order to use a custom Kubernetes Service Account for Redis and/or Sentinel pods, you can set the serviceAccountName in the redis/sentinel spec, if not specified the default Service Account will be used. Note: the operator doesn't create the referenced Service Account resource.

Custom Pod Annotations

By default, no pod annotations will be applied to Redis nor Sentinel pods.

In order to apply custom pod Annotations, you can provide the podAnnotations option inside redis/sentinel spec. An example can be found in the custom annotations example file.

Custom Service Annotations

By default, no service annotations will be applied to the Redis nor Sentinel services.

In order to apply custom service Annotations, you can provide the serviceAnnotations option inside redis/sentinel spec. An example can be found in the custom annotations example file.

Control of label propagation.

By default the operator will propagate all labels on the CRD down to the resources that it creates. This can be problematic if the labels on the CRD are not fully under your own control (for example: being deployed by a gitops operator) as a change to a labels value can fail on immutable resources such as PodDisruptionBudgets. To control what labels the operator propagates to resource is creates you can modify the labelWhitelist option in the spec.

By default specifying no whitelist or an empty whitelist will cause all labels to still be copied as not to break backwards compatibility.

Items in the array should be regular expressions, see here as an example of how they can be used and here for a syntax reference.

The whitelist can also be used as a form of blacklist by specifying a regular expression that will not match any label.

NOTE: The operator will always add the labels it requires for operation to resources. These are the following:

app.kubernetes.io/component
app.kubernetes.io/managed-by
app.kubernetes.io/name
app.kubernetes.io/part-of
redisfailovers.databases.spotahome.com/name

ExtraVolumes and ExtraVolumeMounts

If the user choose to have extra volumes creates and mounted, he could use the extraVolumes and extraVolumeMounts, in spec.redis of the CRD. This allows users to mount the extra configurations, or secrets to be used. A typical use case for this might be

• Secrets that sidecars might use to backup of RDBs
• Extra users and their secrets and acls that could used the initContainers to create multiple users
• Extra Configurations that could merge on top the existing configurations

apiVersion: databases.spotahome.com/v1
kind: RedisFailover
metadata:
  name: redisfailover
spec:
  sentinel:
    replicas: 3
  redis:
    replicas: 3
    extraVolumes:
    - name: foo_user
      secret:
        secretName: mysecret
        optional: false
    exraVolumeMounts:
    - name: foo
      mountPath: "/etc/foo"
      readOnly: true

Connection to the created Redis Failovers

In order to connect to the redis-failover and use it, a Sentinel-ready library has to be used. This will connect through the Sentinel service to the Redis node working as a master. The connection parameters are the following:

url: rfs-<NAME>
port: 26379
master-name: mymaster

Enabling redis auth

To enable auth create a secret with a password field:

echo -n "pass" > password
kubectl create secret generic redis-auth --from-file=password

## example config
apiVersion: databases.spotahome.com/v1
kind: RedisFailover
metadata:
  name: redisfailover
spec:
  sentinel:
    replicas: 3
  redis:
    replicas: 1
  auth:
    secretPath: redis-auth

You need to set secretPath as the secret name which is created before.

Bootstrapping from pre-existing Redis Instance(s)

If you are wanting to migrate off of a pre-existing Redis instance, you can provide a bootstrapNode to your RedisFailover resource spec.

This bootstrapNode can be configured as follows:

What is Bootstrapping?

When a bootstrapNode is provided, the Operator will always set all of the defined Redis instances to replicate from the provided bootstrapNode host value. This allows for defining a RedisFailover that replicates from an existing Redis instance to ease cutover from one instance to another.

Note: Redis instance will always be configured with replica-priority 0. This means that these Redis instances can never be promoted to a master.

Depending on the configuration provided, the Operator will launch the RedisFailover in two bootstrapping states: without sentinels and with sentinels.

Default Bootstrapping Mode (Without Sentinels)

By default, if the RedisFailover resource defines a valid bootstrapNode, only the redis instances will be created. This allows for ease of bootstrapping from an existing RedisFailover instance without the Sentinels intermingling with each other.

Bootstrapping With Sentinels

When allowSentinels is provided, the Operator will also create the defined Sentinel resources. These sentinels will be configured to point to the provided bootstrapNode as their monitored master.

Default versions

The image versions deployed by the operator can be found on the defaults file.

Cleanup

Operator and CRD

If you want to delete the operator from your Kubernetes cluster, the operator deployment should be deleted.

Also, the CRD has to be deleted. Deleting CRD automatically wil delete all redis failover custom resources and their managed resources:

kubectl delete crd redisfailovers.databases.spotahome.com

Single Redis Failover

Thanks to Kubernetes' OwnerReference, all the objects created from a redis-failover will be deleted after the custom resource is.

kubectl delete redisfailover <NAME>

Docker Images

Redis Operator

Documentation

For the code documentation, you can lookup on the GoDoc.

Also, you can check more deeply information on the docs folder.