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I have two AEM servers behind F5. The JMeter script is getting a valid cookie from the first server whereas the script is getting a valid cookie followed by a null value. Because of this behavior, the requests to the second server were erroring out. The reasons the requests were erroring out was because JMeter was replacing the valid cookie with null value. I was able to instruct JMeter to ignore the null value by setting CookieManager.delete_null_cookies to false.

The question of this post is, why would F5 return a null value following a valid cookie. I am really curious since it is happening only for one of the servers behind F5 and since I am not sure if there are other side effects that are yet to be discovered.

This is the picture of the F5 configuration that I got from my admins. Let me know what question I need to ask my admins to point me in the right direction.

Ravisankar S
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it's seems you are using cookies for sticky sessions? - try setting the fallback method too-if memory serves this is based on 'client ip' (effectively round robin) - however if your clients are using a proxy server then all the requests will look like they are coming from the same client IP.

cookies for persistent client sessions (stickyness)

https://f5.com/resources/white-papers/cookies-sessions-and-persistence

Sum1sAdmin
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  • @ Sum1sAdmin Yes, that is correct. We are using sticky sessions. We don't have session cluster / distributed session cache and so wouldn't be able to implement round robin scheme in the near future. While the above suggestion is a good one, it doesn't help me understand why I am getting null from F5 after a valid cookie, when we have Sticky Sessions configured in the load balancer and when tested via JMeter. – Ravisankar S Dec 20 '17 at 09:45
  • How does the problem manifest to the user? is there a specific http error code, and can you monitor for session ids, there should be some irules on the F5 for config - this seems similar https://devcentral.f5.com/questions/jsessionids-with-null-or-empty-values – Sum1sAdmin Dec 20 '17 at 10:13
  • The application starts behaving as if the test user hasn't logged into the application (after it once successfully logs in). On enabling JMeter logs, I found that the valid cookie is being over written by null value that JMeter receives subsequent to receiving a valid cookie. This happens only for one of the VMs behind the F5. – Ravisankar S Dec 22 '17 at 06:41