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Redis Streams scaler with support for Redis Cluster topology

Availability: v2.1+ Maintainer: Community

Trigger Specification

Redis 5.0 introduced Redis Streams which is an append-only log data structure.

One of its features includes Consumer Groups, that allows a group of clients to co-operate consuming a different portion of the same stream of messages.

This specification describes the redis-cluster-streams trigger that scales based on the Pending Entries List (see XPENDING) for a specific Consumer Group of a Redis Stream and supports Redis Cluster topology.

triggers:
- type: redis-cluster-streams
  metadata:
    addresses: localhost:6379 # Required if hosts and ports are not provided. Format - comma separated list of host:port
    hosts: localhost # Comma separated lists of hosts. Required if address is not provided
    ports: "6379" # Comma separated lists of ports. Required if addresses are not provided and hosts has been provided.
    passwordFromEnv: REDIS_PASSWORD # optional (can also use authenticationRef)
    stream: my-stream # Required - name of the Redis Stream
    consumerGroup: my-consumer-group # Required - name of consumer group associated with Redis Stream
    pendingEntriesCount: "10" # Required - number of entries in the Pending Entries List for the specified consumer group in the Redis Stream
    enableTLS: "false" # optional
    # Alternatively, you can use existing environment variables to read configuration from:
    # See details in "Parameter list" section
    addressesFromEnv: REDIS_ADDRESSES # Optional. You can use this instead of `addresses` parameter
    hostsFromEnv: REDIS_HOSTS # Optional. You can use this instead of `hosts` parameter
    portsFromEnv: REDIS_PORTS # Optional. You can use this instead of `ports` parameter

Parameter list:

  • addresses: Comma separated list of hosts and ports of Redis Cluster nodes in the format host:port for example node1:6379, node2:6379, node3:6379

As an alternative to the addresses field, the user can specify hosts and ports parameters.

  • hosts: Comma separated list of hosts of Redis Cluster nodes.

It is not required if addresses has been provided

  • ports: Comma separated list of ports for corresponding hosts of Redis Cluster nodes.

It is only to be used along with the hosts/hostsFromEnv attribute and not required if addresses has been provided

  • passwordFromEnv (optional): Name of the environment variable your deployment uses to get the Redis password.

  • stream: Name of the Redis Stream

  • consumerGroup: Name of the Consumer group associated with Redis Stream

  • pendingEntriesCount: Threshold for the number of Pending Entries List. This is the average target value to scale the workload. Defaults to 5

  • enableTLS: Set this to true if TLS connection to Redis is required. Defaults to false

Some parameters could be provided using environmental variables, instead of setting them directly in metadata. Here is a list of parameters you can use to retrieve values from environment variables:

  • addressesFromEnv: The hosts and corresponding ports of Redis Cluster nodes, similar to addresses, but reads it from an environment variable on the scale target. Name of the environment variable your deployment uses to get the URLs of Redis Cluster nodes. The resolved hosts should follow a format like node1:6379, node2:6379, node3:6379 ....
  • hostsFromEnv: The hosts of the Redis Cluster nodes, similar to hosts, but reads it from an environment variable on the scale target.
  • portsFromEnv: The corresponding ports for the hosts of Redis Cluster nodes, similar to ports, but reads it from an environment variable on the scale target.

Authentication Parameters

The scaler supports two modes of authentication:

Using password authentication

Use the password field in the metadata to specify the name of an environment variable that your deployment uses to get the Redis password.

This is usually resolved from a Secret V1 or a ConfigMap V1 collections. env and envFrom are both supported.

Here is an example:

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: redis-streams-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    name: redis-streams-consumer
  pollingInterval: 15
  cooldownPeriod: 200
  maxReplicaCount: 25
  minReplicaCount: 1
  triggers:
    - type: redis-cluster-streams
      metadata:
        addressesFromEnv: REDIS_ADDRESSES
        passwordFromEnv: REDIS_PASSWORD # name of the environment variable in the Deployment
        stream: my-stream
        consumerGroup: consumer-group-1
        pendingEntriesCount: "10"

Using TriggerAuthentication

You can use TriggerAuthentication CRD to configure the authentication. For example:

apiVersion: v1
kind: Secret
metadata:
  name: redis-streams-password
type: Opaque
data:
  redis_password: <encoded redis password>
---
apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: keda-redis-stream-triggerauth
spec:
  secretTargetRef:
    - parameter: password
      name: redis-streams-password # name of the Secret
      key: redis_password # name of the key in the Secret
---
apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: redis-streams-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    name: redis-streams-consumer
  pollingInterval: 15
  cooldownPeriod: 200
  maxReplicaCount: 25
  minReplicaCount: 1
  triggers:
    - type: redis-cluster-streams
      metadata:
        address: node1:6379, node2:6379, node3:6379
        stream: my-stream
        consumerGroup: consumer-group-1
        pendingEntriesCount: "10"
      authenticationRef:
        name: keda-redis-stream-triggerauth # name of the TriggerAuthentication resource


Currently available scalers for KEDA