ELB - Sticky Sessions

Also called (Session Affinity)

  • It is possible to implement stickiness so that the same client is always redirected to the same instance behind a load balancer.

  • This works for Classic Load Balancers & Application Load Balancers

  • The “cookie” used for stickiness has an expiration date you control.

  • Use case: make sure the user doesn’t lose his session data.

  • Enabling stickiness may bring imbalance to the load over the backend EC2 instances.

  • Application-based Cookies

    • Custom cookie

      • Generated by the target

      • Can include any custom attributes required by the application

      • Cookie name must be specified individually for each target group

      • Don’t use AWSALB, AWSALBAPP, or AWSALBTG (reserved for use by the ELB)

    • Application cookie

      • Generated by the load balancer

      • Cookie name is AWSALBAPP

  • Duration-based Cookies

    • Cookie generated by the load balancer

    • Cookie name is AWSALB for ALB, AWSELB for CLB

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