Or is the idea that I should set $server_name explicitly and just avoid that it defaults to $title, so that my $title can vary but $server_name stays the same?

Change 890903 had a related patch set uploaded (by Dzahn; author: Dzahn):

[operations/puppet@production] doc: fix hostname used in http::blackbox monitoring

https://gerrit.wikimedia.org/r/890903

use "doc.wikimedia.org" as the resource title and apply it on both instances, puppet run will fail with a "duplicate declaration" error because the same $title is used more than once

Resource names need to be unique on a single host, not globally. (Otherwise you could not for example have package { 'ssh-server': ensure => present } on multiple machines!). You can simply have a prometheus::blackbox::check::http resource with the vhost name as the resource title on all the backends.

I can't confirm that. We are applying the same role class to multiple nodes and then getting duplicate declaration errors due to a hardcoded resource names is a common occurence.

What exact error message are you getting in this case?

Change 890903 merged by Dzahn:

[operations/puppet@production] doc: fix hostname used in http::blackbox monitoring

https://gerrit.wikimedia.org/r/890903

setting both server_name and instance_label explicitly while also making sure the resource title is not the same on multiple instances (by using the server hostname) seems to be a solution to this.

https://gerrit.wikimedia.org/r/c/operations/puppet/+/890903/2/modules/profile/manifests/doc.pp

In T330233#8634821, @taavi wrote:

Resource names need to be unique on a single host, not globally. (Otherwise you could not for example have package { 'ssh-server': ensure => present } on multiple machines!).

And you can't, if there are multiple hosts and the same resource title is used more than once, in a loop.

example:

$all_hosts.each |Stdlib::Fqdn $other_host| {
...
prometheus::blackbox::check::http { 'foo:

This way it's the same resource more than once on the same hosts (monitoring or rather prometheus hosts where they get realized).

And it's why for example ensure_packages from stdlib exists and is "only install if it doesn't already exist".

Yes title must be unique, and server_name is generally fine as title as long as we're checking internal services. As you found out this doesn't work too well on public services, we're tracking the issue at T312840 though I haven't had the time/bandwidth to work on it, feedback is welcome on the task too!

I'm also confused as to why prometheus::blackbox::check::http is within a loop on $all_hosts as opposed to declaring it outside of the loop and in the profile, which I'm assuming is going to run on $all_hosts anyways?