KEDA CPU Scaling

Welcome to this guide on implementing CPU-based autoscaling in Kubernetes using KEDA and the built-in Horizontal Pod Autoscaler (HPA). You’ll learn how KEDA monitors CPU metrics, sets thresholds, and dynamically adjusts your pod replicas to match workload demands.

How KEDA Leverages CPU Metrics

KEDA integrates with the Kubernetes HPA to fetch CPU metrics and make scaling decisions. The following diagram illustrates the flow:

The image illustrates the KEDA scaling mechanism, showing how it interacts with CPU resources and the Horizontal Pod Autoscaler (HPA) to manage pod scaling.

Metrics Server exposes CPU usage for each pod.
HPA retrieves metrics and compares against defined thresholds.
KEDA’s ScaledObject configures HPA targets and min/max replica counts.
Pods scale out/in based on real-time CPU usage.

Prerequisites

Before you begin, ensure your cluster meets the following requirements:

Metrics Server is deployed and operational.
Pods specify CPU requests (and optionally limits) to enable accurate metrics.
Kubernetes v1.27+ or compatible version for HPA and Custom Metrics API.

The image outlines KEDA CPU scaling requirements, highlighting the need for a Metrics Server and defining Pod CPU requests or limits.

Defining CPU Requests in Your Deployment

Specify resource requests and limits in your Deployment manifest so the Metrics Server can report CPU usage correctly:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: cpu-app
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: cpu-app
  template:
    metadata:
      labels:
        app: cpu-app
    spec:
      containers:
        - name: app
          image: images.my-company.example/app:v4
          resources:
            requests:
              cpu: "500m"
              memory: "128Mi"
            limits:
              cpu: "1000m"
              memory: "256Mi"

Defining CPU requests ensures the HPA can calculate utilization percentages. If no limits are set, pods can burst beyond the request but HPA will still use the request as the baseline.

Configuring the CPU Trigger in KEDA

KEDA supports two CPU trigger modes:

Mode	Description
Utilization	Percentage of CPU request (e.g., `50` for 50% usage)
AverageValue	Absolute CPU value in millicores (e.g., `250m`)

Example trigger configuration:

triggers:
  - type: cpu
    metadata:
      type: Utilization      # 'Utilization' or 'AverageValue'
      value: "60"            # percentage or absolute value
      containerName: ""      # optional: target specific container

If your pods include sidecar containers (e.g., logging, service mesh), set containerName to your main application container to avoid scaling based on sidecar CPU usage.

Creating the ScaledObject

A ScaledObject ties your Deployment to KEDA’s scaling logic. Below is a sample manifest that scales cpu-app between 1 and 5 replicas when CPU utilization exceeds 50%:

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: cpu-app-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    name: cpu-app         # must match the Deployment name
  minReplicaCount: 1
  maxReplicaCount: 5
  triggers:
    - type: cpu
      metadata:
        type: Utilization
        value: "50"        # CPU utilization threshold

Summary of Key Resources

Resource	Purpose
Metrics Server	Exposes CPU/memory metrics to the Metrics API
Deployment	Defines pod spec with CPU `requests` & `limits`
ScaledObject	Configures KEDA triggers and HPA parameters
HPA	Executes the scaling logic based on CPU metrics

Manual Scaling

Horizontal Pod Autoscaler (HPA)

Vertical Pod Autoscaler (VPA)

Cluster Proportional Autoscaler (CPA)

Kubernetes Event-Driven Autoscaling (KEDA)

Introduction

How KEDA Leverages CPU Metrics

Prerequisites

Defining CPU Requests in Your Deployment

Configuring the CPU Trigger in KEDA

Creating the ScaledObject

Summary of Key Resources

References

Watch Video

Practice Lab

​How KEDA Leverages CPU Metrics

​Prerequisites

​Defining CPU Requests in Your Deployment

​Configuring the CPU Trigger in KEDA

​Creating the ScaledObject

​Summary of Key Resources

​References

Watch Video

Practice Lab

How KEDA Leverages CPU Metrics

Prerequisites

Defining CPU Requests in Your Deployment

Configuring the CPU Trigger in KEDA

Creating the ScaledObject

Summary of Key Resources

References