Manual:$wgEnableWANCacheReaper

Whether to verify and enforce WAN cache purges using reliable DB sources as streams.

Details
Set to true to verify and enforce WAN cache purges using reliable DB sources as streams.

These secondary cache purges are de-duplicated via simple cache mutexes. This improves consistency when cache purges are lost, which becomes more likely as more cache servers are added or if there are multiple datacenters. Only keys related to important mutable content will be checked.