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-streams trigger that scales based on the Pending Entries List (see XPENDING) for a specific Consumer Group of a Redis Stream.

triggers:
- type: redis-streams
  metadata:
    address: REDIS_SERVER # Required if host and port are not provided. Format - host:port
    host: REDIS_HOST # Required if address is not provided
    port: REDIS_PORT # Required if address is not provided and host has been provided
    password: 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
    databaseIndex: "0" # optional

Parameter list:

• address: Name of the environment variable your deployment uses to get the Redis server URL. The resolved host should follow a format like my-redis:6379.
  • This is usually resolved from a Secret V1 or a ConfigMap V1 collections. env and envFrom are both supported.

As an alternative to the address field, the user can specify host and port parameters.

• host: Name of the environment variable your deployment uses to get the Redis server host.
  • This is usually resolved from a Secret V1 or a ConfigMap V1 collections. env and envFrom are both supported.

It is not required if address has been provided

• port: Name of the environment variable your deployment uses to get the Redis server port.
  • This is usually resolved from a Secret V1 or a ConfigMap V1 collections. env and envFrom are both supported.

It is only to be used along with the host attribute and not required if address has been provided

• password (optional): Name of the environment variable 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.

• 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

• databaseIndex: The Redis database index. Defaults to 0 if not specified

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

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
  labels:
    deploymentName: redis-streams-consumer
spec:
  scaleTargetRef:
    deploymentName: redis-streams-consumer
  pollingInterval: 15
  cooldownPeriod: 200
  maxReplicaCount: 25
  minReplicaCount: 1
  triggers:
    - type: redis-streams
      metadata:
        address: REDIS_HOST
        password: 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: YWRtaW4=
---
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
  labels:
    deploymentName: redis-streams-consumer
spec:
  scaleTargetRef:
    deploymentName: redis-streams-consumer
  pollingInterval: 15
  cooldownPeriod: 200
  maxReplicaCount: 25
  minReplicaCount: 1
  triggers:
    - type: redis-streams
      metadata:
        address: REDIS_HOST
        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