HomePhabricator

Lower CDN cache TTL when slave lag is high

Description

Lower CDN cache TTL when slave lag is high

  • $wgCdnMaxageLagged controls exactly what that TTL is and the usual "max lag" settings determine what "high" is for lag (which already makes the site read-only).
  • This helps avoids stale content getting stuck in CDN for a month just because a slave was lagged for a minute. Of course race conditions with normal slave lag and WAN cache relay purges can still lead to this problem, though the scope of it is reduced.

Bug: T113204
Change-Id: I7ff0a8d88665f4e557566e7b412e75edee2627fe