Continued:

- moved if() block to suggested position by MrPetovan, for me I want to have all
  conditions checked at the start of the method, e.g. no unwanted null
  references or (in this case) if the URL is blacklisted
- normalized URLs are without SSL, means http://host/path/file.ext so they exist
  only once for contacts and servers (aka. instances)
- documented returned type `void`

src/Worker/UpdateServerPeers.php

@@ -63,7 +63,7 @@ class UpdateServerPeers
 			}
 
 			++$total;
-			if (DBA::exists('gserver', ['nurl' => Strings::normaliseLink('https://' . $peer)])) {
+			if (DBA::exists('gserver', ['nurl' => 'http://' . $peer])) {
 				// We already know this server
 				continue;
 			}