What is KEDA and how to use event-driven autoscaling?

Question

Accepted Answer

**KEDA (Kubernetes Event-Driven Autoscaler)** — Pod scaling based on external metrics (message queues, cron, HTTP).

**HPA limitation:** HPA only uses CPU/Memory. KEDA supports Kafka, RabbitMQ, Redis, SQS, etc.

**Installation:**
```bash
helm repo add kedacore https://kedacore.github.io/charts
helm install keda kedacore/keda --namespace keda --create-namespace
```

**ScaledObject for Kafka:**
```yaml
apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: kafka-consumer
  namespace: production
spec:
  scaleTargetRef:
    name: kafka-consumer
  minReplicaCount: 1
  maxReplicaCount: 50
  triggers:
    - type: kafka
      metadata:
        bootstrapServers: kafka:9092
        consumerGroup: my-group
        topic: orders
        lagThreshold: "100"
    - type: cron
      metadata:
        timezone: Europe/Moscow
        start: "0 8 * * 1-5"
        end: "0 20 * * 1-5"
        desiredReplicas: "5"
```

**ScaledObject for RabbitMQ:**
```yaml
- type: rabbitmq
  metadata:
    host: amqp://user:pass@rabbitmq:5672/
    queueName: tasks
    queueLength: "50"
```

**Supported scalers:** Kafka, RabbitMQ, Redis, AWS SQS, Azure Service Bus, Prometheus, Cron, HTTP, PostgreSQL, MySQL.

DevOps: What is KEDA and how to use event-driven autoscaling?