Background

poolcounter05 and poolcounter06.deployment-prep.eqiad1.wikimedia.cloud were shutdown in T370458: Remove or replace poolcounter06.deployment-prep.eqiad1.wikimedia.cloud (Buster deprecation) despite being used actively used by MediaWiki and Thumbor.

https://codesearch.wmcloud.org/search/?q=deployment-poolcounter

thumbor::poolcounter_server: deployment-poolcounter05.deployment-prep.eqiad.wmflabs

		'poolcounter' => [
			'deployment-poolcounter06.deployment-prep.eqiad.wmflabs',
		],

In T370458#10037556, @akosiaris wrote:

Found this from T332015 and a simple question on my side is, does anyone know why this VM needs to exist? Aside from "this is how it is in production", […], isn't a very good answer.

It's not so much existing, as behaving making services behave substantially different. Eg. MediaWiki with and without serving stale content and coellescing Parser invocations, and MW CirrusSearch with and without throttle, and Thumbor (or MW image scaling) with or without throttling.

I imagine this is likely causing logspam at the moment, making it harder to diagnose other issues.
And in terms of testing, this will of course decrease the value of testing, e.g. thumbnails are generated concurrently without limits which has often been the source of bugs in production and would benefit from behaving the same in Beta. Likewise, fast-serving stale ParserOutput is the kind of thing that can catch people off-guard. The earlier people notice this the better.