My app does not pick up the changed hostname on my VPS

jdj_dk

Hi everyone.

I’m trying to setup a small cluster with three nodes. I’m using libcluster as I have before. But my nodes doesn’t have a usable hostname. The VPS came with a hostname like this: ip-123-123-123-123. I’ve changed the hostname on the VPS but it doesn’t get picked up in the app when I restart it. I’ve restarted the server. And i can see that the hostname has changed on the server it self.

I’m seeing in the logs when it starts that it’s using the old hostname, which included the IP of the vps. So I get this error:

21:36:48.538 [error] ** System running to use fully qualified hostnames **
: ** Hostname ip-x-x-x-x is illegal **

The app is built using Mix release. From the docs I can see that I should be able to set RELEASE_DISTRIBUTION and RELEASE_NODE env variables. I’ve set them to the following:

RELEASE_DISTRIBUTION=name
RELEASE_NODE=app_name@host.url.com

I would assume doing so would force change the hostname in the app as well. But it doesn’t seem to be the case. What am I missing. Thanks in advance

19 comments

#deployment #troubleshooting #cluster

0 2284 19

2025-10-12 13:04:17 UTC

Showing Posts 1 to 10

Show Best Posts
Show All (oldest first)
Show All (newest first)

LostKobrakai

This is what I found when looking for what makes an hostname valid as opposed to illegal. Maybe you’re missing the resolvable and reachable part.

Long names need the hostname to be resolvable and reachable, in other words it needs to either be an IP address or a valid DNS name. In the case of an IP address, it is already resolved so it only needs to be reachable from the current host. In the case of a DNS name, it needs to be resolvable by any one of the DNS resolution mechanisms on the host (/etc/hosts, /etc/resolve.conf, etc.) to an IP address which is reachable from the current host.

https://github.com/bitwalker/distillery/issues/338#issuecomment-334848537

Post #1

jdj_dk

Thanks for your answer.

The hostname is indeed resolvable and reachable. But it doesn’t seem to pick up the hostname at all in my app. That’s the problem I think.

It keeps using the original hostname the VPS had when it was first setup. Now the hostname has changed to something that is reachable from the outside world as well. But it doesn’t seem to pick up the host name even though I set it explicitly with tne RELEASE_NODE env variable.

Post #2

NobbZ

Where and how did you change those?

Post #3

jdj_dk

I changed the hostname in /etc/hostname and rebooted the server.

The RELEASE_NODE & RELEASE_DISTRIBUTION env variables is set in the systemd service responsible for keeping the app running

Post #4

Exadra37

If the output of both hostname and hostname -f are not the same then I think your hostname is not set properly.

Try to set it with:

sudo hostnamectl set-hostname something.example.com

Post #5

jdj_dk

Thanks for your input.

The output of both hostname and hostname -f are the same.

I tried setting the hostname with your command. Sadly it didn’t make any difference.

Post #6

Exadra37

Maybe moving the Elixir configuration for http and url and anything not related with compile time settings into runtime.exs and build a new release can help?

Post #7

jdj_dk

Yeah I already did that and that works fine. But the node it self doesn’t get the correct host.

Post #8

Exadra37

So, how are you setting up the nodes configuration?

Post #9

jdj_dk

So, how are you setting up the nodes configuration?

What exactly do you mean by nodes configuration? Then only thing I’m trying now is to make sure my node has the right hostname (using RELEASE_NODE & RELEASE_DISTRIBUTION ) so I can connect to it from another node. After that I’m setting up libcluster.

Post #10

Load more posts (9 remaining)