Tag: Question 256

AWS Certified SysOps Administrator SOA-C01 – Question256

A sys admin is trying to understand the sticky session algorithm. Please select the correct sequence of steps, both when the cookie is present and when it is not, to help the admin understand the implementation of the sticky session:
1. ELB inserts the cookie in the response
2. ELB chooses the instance based on the load balancing algorithm
3. Check the cookie in the service request
4. The cookie is found in the request
5. The cookie is not found in the request


A. 3,1,4,2 [Cookie is not Present] & 3,1,5,2 [Cookie is Present]
B. 3,4,1,2 [Cookie is not Present] & 3,5,1,2 [Cookie is Present]
C. 3,5,2,1 [Cookie is not Present] & 3,4,2,1 [Cookie is Present]
D. 3,2,5,4 [Cookie is not Present] & 3,2,4,5 [Cookie is Present]

Correct Answer: C

Explanation:

Explanation: Generally, AWS ELB routes each request to a zone with the minimum load. The Elastic Load Balancer provides a feature called sticky session which binds the user’s session with a specific EC2 instance. The load balancer uses a special load-balancer-generated cookie to track the application instance for each request. When the load balancer receives a request, it first checks to see if this cookie is present in the request. If so, the request is sent to the application instance specified in the cookie. If there is no cookie, the load balancer chooses an application instance based on the existing load balancing algorithm. A cookie is inserted into the response for binding subsequent requests from the same user to that application instance.