You have written an application that uses the Elastic Load Balancing service to spread traffic to several web
servers. Your users complain that they are sometimes forced to login again in the middle of using your
application, after they have already logged in. This is not behavior you have designed.
What is a possible solution to prevent this happening?
A.
Use instance memory to save session state.
B.
Use instance storage to save session state.
C.
Use EBS to save session state
D.
Use ElastiCache to save session state.
E.
Use Glacier to save session slate.
D
http://www.aiotestking.com/amazon/what-is-a-possible-solution-to-prevent-this-happening/
D. Use ElastiCache to save session state.
Using the default provider, your ELB must send every request from a specific user to the same web server. This is known as sticky sessions and greatly limits your elasticity. First, the ELB cannot distribute traffic evenly, often sending a disproportionate amount of traffic to one server. Second, Auto Scaling cannot terminate web servers without losing some user’s session state.
By moving the session state to a central location, all the web servers can share a single copy of session state. This allows the ELB to send requests to any web server, better distributing load across all the web servers. In addition, Auto Scaling can terminate individual web servers without losing session state information.
The two options to move the session state to a central location are:
1) DynamoDB Session State Provider that ships with the AWS SDK
2) Storing session state in an ElastiCache cluster (ElastiCache supports both Memcached and Redis cache clusters)
So answer is D: “Use ElastiCache to save session state.”