403 - Forbidden: Access is denied in JMeter

Question

I'm facing an issue while doing the load testing through Jmeter. I hosted my dot net application in AWS and added all my images through CDN. While doing the load test through Jmeter, I'm getting 403 Access denied error. But if I run single users it seems to be working. When I run concurrent users more than 2 I'm getting the error. Can anyone please support on this

Answer 1

Possibly it is because of some sort of firewall & DDOS protection of AWS cloud. It blocks concurrent users from same IP address sending request at the same time. You can try adding your ip address to the whitelist or you can close the firewall & DDOS protection if you are able to.

Answer 2

Without knowing the infrastructure details it's not possible to come up with a comprehensive answer so I can only provide some generic steps

1. Check out your application logs, there might be some information there
2. Check your CDN settings, there might be some restrictions there
3. Make sure to properly correlate the requests as it might be the case you recorded the request for one user which runs successfully and fails for the 2nd and subsequent users because application doesn't allow concurrent logins or so
4. Try launching JMeter in AWS as well, the same region or even VPC so the requests won't be considered "alien" by your application
5. You could try setting up IP Spoofing so each user would use its own IP address or alias, however if you're behind NAT it might not work
6. If your deployment is protected by i.e. AWS Shield check if you getting a common error with more meaningful message/cause than just "access denied" which is pretty "umbrella" for all "Forbidden" response status codes