Constant CAMEL_CACHE_INVALIDATED_COUNT 

pub const CAMEL_CACHE_INVALIDATED_COUNT: &str = "CamelCacheInvalidatedCount";

Exchange property set to the number of entries removed by a successful cache_invalidate step — always 1 for exact-key (removal is not observable by the backend), the returned count for a namespace purge. Not set when the key/prefix expression resolves to None or the backend reports an error.