Resolved 504 timeout once old server is turned off after migrating to new server via Plesk

[hillcow]

So this is a rather strange error. After migrating my websites via Plesk Migrator to my new server (from Ubuntu to Debian), I get a 504 error when trying to access one of my websites. However, once I turn on the old server everything works just fine. Which is strange, because the domain points to the new IP now of course and DNS settings should be fine too (see below). Confusingly enough, other websites managed via Plesk work.

How would you approach this error?

Comparison of DNS settings inside Plesk of the website that is not working and a website that is working (default settings anyway)

 

[Kingsley]

debian 9?

i will advise you check your DNS records and template properly.

 

[hillcow]

I actually just found the error.

So, this was a tough case. I've spent so many evenings trying different setups, switching operating systems, different DNS settings, etc. - when in the end, this had nothing to do with the server itself. It was a simple script that was fetching a rss feed from another of my websites which I don't run anymore. It's domain still pointed to the old server. With the old server being turned off, the script did not respond whatsoever and that's the timeout.

I've never been so satisfied finding a bug, wooohoo.

 

[Kingsley]

nice congrats

 

[mr-wolf]

Before dismantling a server that has been in service for many years one should turn on verbose logging on all services and check if nothing is accessing it...
Troubleshooting this could have been done starting with

tcpdump -A host <oldserverIP>
or
tcpdump -A net <oldserverNET>

 

[hillcow]

Before dismantling a server that has been in service for many years one should turn on verbose logging on all services and check if nothing is accessing it...
Troubleshooting this could have been done starting with

tcpdump -A host <oldserverIP>
or
tcpdump -A net <oldserverNET>

Thank you. Yes, that would have been very helpful I guess.