ELB health check history / log

Question

I have an ELB (Network Load Balancer with a couple of Auto Scaling Groups as Target Group) that has periodical health check fails (i.e. some instances would be marked as unhealthy and then recover after a few minutes). The health check is a simple static page (i.e. /health_check).

The timing seems to be at the same time when the host is having heavy network load (downloading large files from S3), but I want to have more information (e.g. they are failing the active health check or passive health check as mentioned in https://docs.aws.amazon.com/elasticloadbalancing/latest/network/target-group-health-checks.html).

However, I am not able to find the health check history or logs from ELB. All my search finds is about the Access Log for ELB (https://docs.aws.amazon.com/elasticloadbalancing/latest/network/load-balancer-access-logs.html) which is about the actual user requests.

Is this health check history / log accessible anywhere?

Supersede

I'm in pretty much the same situation. Once every 12 to 24 hours my NLB decides that my fargate service is "unhealthy" and spins up a new instance to replace it, only to tear down the fresh instance 5 minutes later when the original one recovers to a "healthy" state. Everything looks totally fine in the application logs, so I have no idea why its getting flagged as unhealthy. Is there truly no way to see the "reason codes" associated with past health check failures? I just have to get lucky and catch it during one of those 5 minute windows? – Speedway

Answer 1

Elastic Load Balancing does not log health check requests.

reference

Jaipur