Which recommendations can help ensure load-testing HTTP requests are evenly distributed across the four webser

A startup s photo-sharing site is deployed in a VPC. An ELB distributes web traffic across
two subnets. ELB session stickiness is configured to use the AWS-generated session
cookie, with a session TTL of 5 minutes. The webserver Auto Scaling Group is configured
as: min-size=4, max-size=4. The startups preparing for a public launch, by running
load-testing software installed on a single EC2 instance running in us-west-2a. After 60
minutes of load-testing, the webserver logs show: Which recommendations can help ensure
load-testing HTTP requests are evenly distributed across the four webservers? Choose 2
answers.

A.
Re-configure the load-testing software to re-resolve DNS for each web request.

B.
Use a 3rd-party load-testing service which offers globally-distributed test clients.

C.
Configure ELB and Auto Scaling to distribute across us-west-2a and us-west-2c.

D.
Configure ELB session stickiness to use the app-specific session cookie.

E.
Launch and run the load-tester EC2 instance from us-east-1 instead.

9 Comments on “Which recommendations can help ensure load-testing HTTP requests are evenly distributed across the four webser

  1. Greg says:

    B and D
    A is wrong because the ELB is directing the traffic
    B would bypass stickyness
    C is silly
    D would apply the 5 minute TTL of the application session
    E is also silly

    1. Greg says:

      I mis-read this one. it is A and B. If session Stickeness of the ELB Cookie TTL was set to 60 minutes and the App cookie session TTL was set to a lower number (5 minutes) then A would be Trumped, however, since the ELB cookie is already set to 5 minutes and the test is 60 minutes long then A and B would work and are the simplest choices.

  2. blahblah says:

    Answer: A and B

    C – does not solve anything. It just moves the vms from us-west-2b to us-west-2c, leaving the same problem
    D – Does not solve the problem. Just like the orig cookies w/ ttl 5 min.s over a 60 min period did not solve it, just offloading to the app won’t either as the ELB still handles distribution while the app handles the timer until cookie expiration, which won’t change distribution.
    E – Also, does not solve the problem as your sticky sessions and single client will force the ELB to use the same backend resources over and over, not distributing the load.

    https://aws.amazon.com/articles/1636185810492479

    If your configuration leverages session affinity, then it is important for the load generator to use multiple clients, so that Elastic Load Balancing can behave as it would in the real world. If you do not make these adjustments, then Elastic Load Balancing will always send requests to the same back-end servers

    If clients do not re-resolve the DNS at least once per minute, then the new resources Elastic Load Balancing adds to DNS will not be used by clients. This can mean that clients continue to overwhelm a small portion of the allocated Elastic Load Balancing resources

    If sticky sessions are enabled, it is critical that the load test framework not re-use connections and clients in the tests, but rather it creates unique clients for each request. If this is not done, then the clients will constantly send traffic to the same Elastic Load Balancing resources


Leave a Reply

Your email address will not be published. Required fields are marked *