AWS load balancer UnHealthyHostCount / failed health checks

I am looking for an expert who can assist me with troubleshooting and setup for my Classic Load Balancer on AWS. The website is currently not reachable due to an error in the load balancer. I have specific error messages and logs related to the failed health checks that I can provide.

Skills and Experience:
- Strong knowledge and experience with AWS load balancers, specifically Classic Load Balancer
- Proficient in troubleshooting and resolving load balancer issues
- Familiarity with analyzing error messages and logs to identify and fix health check failures


ERROR MSG:
Hello,

Warm greetings from AWS premium support.

Thank you for reaching out to us with your concern. My name is Hope from AWS Networking Support Team and I appreciate the opportunity to assist you with this case today.

From the case description, I understand that your domain isn't reachable and you have nothing changed, the domain is paid & active and you want to know what went wrong?

I had a look at the hosted zone for domain bilesucentrs.lv and I see that the domain is resolving without any issues:

$ dig bilesucentrs.lv

; <<>> DiG 9.16.38-RH <<>> bilesucentrs.lv
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42499
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;bilesucentrs.lv. IN A

;; ANSWER SECTION:
bilesucentrs.lv. 60 IN A 13.53.159.122
bilesucentrs.lv. 60 IN A 16.170.51.251

;; Query time: 180 msec
;; SERVER: 10.0.0.2#53(10.0.0.2)
;; WHEN: Thu Jul 06 11:22:33 UTC 2023
;; MSG SIZE rcvd: 76

I further see that your domain is pointing to a loadbalancer with name xxx.amazonaws.com, looking at this load balancer UnHealthyHostCount metric I see that the targets failed health checks:

I further ran the curl command to the domain name and got the below output:

curl -Iv bilesucentrs.lv
* Trying 16.170.51.251:80...
* Connected to bilesucentrs.lv (16.170.51.251) port 80 (#0)
> HEAD / HTTP/1.1
> Host: bilesucentrs.lv
> User-Agent: curl/8.0.1
> Accept: */*
>
* Empty reply from server
* Closing connection 0
curl: (52) Empty reply from server

I got the message "Empty reply from server" and the connection was closed, this indicates issue with the backend targets which now failed health checks and you need to look at the target if the application is working.

I trust that the above information is helpful. However, please don't hesitate to reach me back if you still have concerns. I will be happy to assist.

Have an awesome day further!

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