Question Issues with magento 2, varnish, ngin x

[pfrenn]

Subject: Varnish with Docker Not Connecting to Backend – Error 503

Hi,

I’ve followed the official Plesk instructions for configuring Varnish with Magento 2 ( How to configure varnish cache for a domain in Plesk? - Support Cases from Plesk Knowledge Base ), and also checked other guides like the one on dx3webs.com (both are simimlar Configure Varnish for Magento 2 on Plesk ), but I’m encountering several issues.

1. IP Address Confusion: The guide refers to the IP 172.17.0.0/24. Is this IP the local server’s IP or a placeholder for a different IP address?

2. Connection Refused: When I try to verify the configuration by running curl http://<anonymised>:7080, I get the error:
curl: (7) Failed to connect to <anonymised> port 7080 after 0 ms: Connection refused

3. Docker Container Logs: The Docker container is showing the following errors:
Debug: Version: varnish-6.5.1 revision 1dae23376bb5ea7a6b8e9e4b9ed95cdc9469fb64
Debug: Platform: Linux,5.15.0-139-generic,x86_64,-junix,-smalloc,-sdefault,-hcritbit
Debug: Child (18) Started
Info: Child (18) said Child starts
Error: Manager got SIGTERM
Debug: Stopping Child
Info: Child (18) ended
Info: Child (18) said Child dies
Debug: Child cleanup complete
Info: manager stopping child
Info: manager dies
Warnings:
VCL compiled.

Debug: Version: varnish-6.5.1 revision 1dae23376bb5ea7a6b8e9e4b9ed95cdc9469fb64
Debug: Platform: Linux,5.15.0-139-generic,x86_64,-junix,-smalloc,-sdefault,-hcritbit
Debug: Child (18) Started
Info: Child (18) said Child starts

4. Varnish Configuration (inside docker 6.5.1 container):
backend default {
.host = "<anonymised>";
.port = "7080";
.first_byte_timeout = 600s;
.probe = {
.url = "/pub/health_check.php";
.timeout = 2s;
.interval = 5s;
.window = 10;
.threshold = 5;
}
}
acl purge {
"localhost";
"<anonymised>";
}

5. Error 503: When I try to access the domain, I get the error:
Error 503 Backend fetch failed
Backend fetch failed
Guru Meditation:
XID: 65557

6. Questions:
- How can I get the Docker container up and running properly?
- Is the Nginx configuration related to Docker's proxy setting as mentioned in the instructions? If so, how is it connected?

Any help with troubleshooting the backend connection or understanding the role of Nginx here would be greatly appreciated.

Thanks in advance!