AWS ELB Returns 502

0
votes

I have an EC2 instance (Instance-A) that sits behind an ELB (single instance at the moment). The server runs on Wildfly 11.

Target group shows the instance is healthy. And I can use curl using ip address from another instance (Instance-B) in a different vpc.

But it returns 502 when I curl the ELB dns name from Instance-B. Any idea where to look at?

Access log entry,

http 2019-11-11T22:57:04.899824Z app/DummyELB-2/b71c4db727f11413 172.31.14.179:60746 10.1.4.217:80 -1 -1 -1 502 - 127 293 "GET http://internal-dummyelb-2-1122730003.ap-southeast-2.elb.amazonaws.com:80/ HTTP/1.1" "curl/7.61.1" - - arn:aws:elasticloadbalancing:ap-southeast-2:xxx:targetgroup/DummyTG-2/738f12f02eeddb57 "Root=1-5dc9e740-f43a035fdc04fec2373217d6" "-" "-" 0 2019-11-11T22:57:04.898000Z "forward" "-" "-" "10.1.4.217:80" "-"

- Update -

The ELB is internal and the instance is private. I also have a separate private instance (with a index.html on apache server) and an internal ELB that has no problem with curling ELB DNS.

2
amazon-web-servicesamazon-ec2amazon-elbwildfly-11
are u using public or private hostname? – Juned Ahsan
Updated the original question. – mumbo_s5

2 Answers

1
votes

It seems you are either using a private load balancer or hitting the private hostname as per the domain in your logs

http://internal-dummyelb-2-1122730003.ap-southeast-2.elb.amazonaws.com:80/

Private hosts will only be resolved within the VPC. You can resolve the private hostname in peered VPC but that requires extra configuration. More information for that here:

https://docs.aws.amazon.com/vpc/latest/peering/modify-peering-connections.html

Check the section : Enabling DNS Resolution Support for a VPC Peering Connection

0
votes

It was a problem with how I setup forwarding requests to port 8080 in the target group. I have set the override port to 8080 in the health check rather than in target group.

Once I fixed it, my ELB managed to forward requests correctly.