Session Affinity

January 22, 2025 · View on GitHub

Overview

Session affinity (also known as sticky sessions) ensures that requests from the same client are consistently routed to the same backend pod. In Kubernetes, sessionAffinity refers to a mechanism that allows a client to always be redirected to the same pod when the client hits a service.

Configuration

Basic Setup

Enable session affinity by setting service.spec.sessionAffinity to ClientIP:

apiVersion: v1
kind: Service
metadata:
  name: wordpress-lsmnl-wordpress
  namespace: wordpress-lsmnl
  labels:
    app: wordpress-lsmnl-wordpress
spec:
  type: LoadBalancer
  selector:
    app: wordpress-lsmnl-wordpress
  sessionAffinity: ClientIP

Setting Timeout

Configure the maximum session sticky time using sessionAffinityConfig:

apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  type: LoadBalancer
  sessionAffinity: ClientIP
  sessionAffinityConfig:
    clientIP:
      timeoutSeconds: 10800  # 3 hours

Configuration Options

Session Affinity Types

None: No session affinity (default)
ClientIP: Route based on client's IP address. All requests from the same client IP will be directed to the same pod.

Timeout Configuration

timeoutSeconds: Duration to maintain affinity
Default: 10800 seconds (3 hours)
Valid range: 1 to 86400 seconds (24 hours)
After the timeout period, client requests may be routed to a different pod