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I've set up an Application Load Balancer that points to a Fargate Cluster's service (via a target group). I'm using a security group for both the ALB and the service. When I specify specific IP addresses, the TG health checks fail. It works fine when I include the TG health checker's IPs (2 of them), but that's unsustainable for obvious reasons.

I've tried to use 2 different SGs: 1 for the ALB, and the other for the service. The SG has specific IP inbound rules, and the SG for the service allows all inbound traffic (any IP).

Unfortunately, that doesn't work. Does anyone have any suggestions on how to set this up properly?

Thanks in advance!

Bennybear
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  • We really need more information: Q: What's the specific error code (or error message, if you have one)? Q: Does it always work with IP addresses, and always fail with hostnames? SUGGESTIONS: look [here](https://docs.aws.amazon.com/elasticloadbalancing/latest/application/target-group-health-checks.html) and [here](https://aws.amazon.com/premiumsupport/knowledge-center/ecs-fargate-health-check-failures/). Follow *ALL* the tips. [Edit] your post with the additional information (including, hopefully, the resolution). – paulsm4 Dec 27 '21 at 01:45
  • There is no specific message. The traffic never gets to my instance because the Healthchecker tries to get to it but it times out, so it fails, causing the target group to drain the availability zone. The SG groups allow specific IPs when I include the specific IP addresses of the Healthchecker. – Bennybear Dec 27 '21 at 04:47
  • Sigh... Did you read all of the information in the links? For example, did you try [describe-target-health](https://docs.aws.amazon.com/cli/latest/reference/elbv2/describe-target-health.html), or try increasing the timeout? I *suspect* the problem *might* be name resolution (hence my question about IPs). But you need to dig deeper, and try everything possible to get more information. Start by re-reading the two links I cited, and please [Edit] your post with any additional information you find. – paulsm4 Dec 27 '21 at 06:30

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