(Not an unbreak now because the code to be deployed is not critical)
While deploying a change for mysql configuration due to a hardware failure (T103230), all proxys and nodes failed to sync:
root@tin:/srv/mediawiki-staging$ sync-file wmf-config/db-eqiad.php "Depool db1028, return ES servers back from maintenance" ... 09:28:41 ['/srv/deployment/scap/scap/bin/sync-common', '--no-update-l10n', '--include', 'wmf-config', '--include', 'wmf-config/db-eqiad.php', 'mw1010.eqiad.wmnet', 'mw1033.eqiad.wmnet', 'mw1070.eqiad.wmnet', 'mw1097.eqiad.wmnet', 'mw1216.eqiad.wmnet', 'mw1161.eqiad.wmnet', 'mw1201.eqiad.wmnet', 'mw2001.codfw.wmnet', 'mw2041.codfw.wmnet', 'mw2080.codfw.wmnet', 'mw2119.codfw.wmnet', 'mw2187.codfw.wmnet'] on mw2136.codfw.wmnet returned [255]: Permission denied (publickey). sync-common: 100% (ok: 0; fail: 466; left: 0) 09:28:41 466 apaches had sync errors 09:28:41 Finished sync-apaches (duration: 00m 03s) 09:28:41 Synchronized wmf-config/db-eqiad.php: Depool db1028, return ES servers back from maintenance (duration: 00m 03s)
This was a hardware maintenance deployment, and I can live without it because mediawiki detects it and depools automatically, but it would be an unbreak now in other cases.
I remember bblack talking about deployment key changes, probably related.
Related: T110791 T110793