Apache Kafka

Scale applications based on an Apache Kafka topic or other services that support Kafka protocol.

Availability: v1.0+ Maintainer: Microsoft

Notice:

No. of replicas will not exceed the number of partitions on a topic. That is, if maxReplicaCount is set more than number of partitions, the scaler won’t scale up to target maxReplicaCount.
This is so because if there are more number of consumers than the number of partitions in a topic, then extra consumer will have to sit idle.

Trigger Specification

This specification describes the kafka trigger for an Apache Kafka topic.

triggers:
- type: kafka
  metadata:
    # brokerList: kafka.svc:9092 - deprecated
    bootstrapServers: kafka.svc:9092
    consumerGroup: my-group
    topic: test-topic
    lagThreshold: '5'

Parameter list:

brokerList - Comma separated list of Kafka brokers “hostname:port” to connect to for bootstrap (DEPRECATED).
bootstrapServers - Comma separated list of Kafka brokers “hostname:port” to connect to for bootstrap.
consumerGroup - Consumer group used for checking the offset on the topic and processing the related lag.
topic - Topic on which processing the offset lag.
lagThreshold - How much the stream is lagging on the current consumer group. Default is 10. Optional.

Authentication Parameters

You can use TriggerAuthentication CRD to configure the authenticate by providing authMode, username, password. If your kafka cluster does not have sasl authentication turned on, you will not need to pay attention to it.

Credential based authentication:

authMode - Kafka sasl auth mode. (Values: none, sasl_plaintext, sasl_ssl, sasl_ssl_plain, sasl_scram_sha256, sasl_scram_sha512. Default: none, Optional)
username - (Optional)
password - (Optional)
ca - Certificate authority file for TLS client authentication sasl_ssl. (Optional)
cert - Certificate for client authentication sasl_ssl. (Optional)
key - Key for client authentication with sasl_ssl. Optional)

Example

Your kafka cluster no sasl auth:

apiVersion: keda.k8s.io/v1alpha1
kind: ScaledObject
metadata:
  name: kafka-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    deploymentName: azure-functions-deployment
  pollingInterval: 30
  triggers:
  - type: kafka
    metadata:
      bootstrapServers: localhost:9092
      consumerGroup: my-group       # Make sure that this consumer group name is the same one as the one that is consuming topics
      topic: test-topic
      # Optional
      lagThreshold: "50"

Your kafka cluster turn on sasl auth

apiVersion: v1
kind: Secret
metadata:
  name: keda-kafka-secrets
  namespace: default
data:
  authMode: "sasl_plaintext"
  username: "admin"
  password: "admin"
  ca: <your ca>
  cert: <your cert>
  key: <your key>
---
apiVersion: keda.k8s.io/v1alpha1
kind: TriggerAuthentication
metadata:
  name: keda-trigger-auth-kafka-credential
  namespace: default
spec:
  secretTargetRef:
  - parameter: authMode
    name: keda-kafka-secrets
    key: authMode
  - parameter: username
    name: keda-kafka-secrets
    key: username
  - parameter: password
    name: keda-kafka-secrets
    key: password
  - parameter: ca
    name: keda-kafka-secrets
    key: ca
  - parameter: cert
    name: keda-kafka-secrets
    key: cert
  - parameter: key
    name: keda-kafka-secrets
    key: key
---
apiVersion: keda.k8s.io/v1alpha1
kind: ScaledObject
metadata:
  name: kafka-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    deploymentName: azure-functions-deployment
  pollingInterval: 30
  triggers:
  - type: kafka
    metadata:
      bootstrapServers: localhost:9092
      consumerGroup: my-group       # Make sure that this consumer group name is the same one as the one that is consuming topics
      topic: test-topic
      # Optional
      lagThreshold: "50"
    authenticationRef:
      name: keda-trigger-auth-kafka-credential