[keycloak-dev] Cache policies and cache clearing

[Bill Burke]

I found out that if you call cache.clear() with a invalidation cache, it 
only clears locally and not the entire cluster.  I was thinking that we 
could set a realm attribute of "not-valid-before" with a timestamp.  
When something is accessed, check the timestamp vs. the time the thing 
was inserted into the cache.

This is also important for the fine-grain cache policies I want to 
implement for users.  I want cache policies for users. Scheduled 
evictions and/or max time in the cache.  There could be realm-level 
policies for all users everywhere, and per storage provider.  I also 
want the ability to clear the cache for a specific provider manually.  
Using the Infinispan stream() api, IMO, is just not feasible.  We don't 
want to be iterating over thousands of users in the cache to see if they 
should be invalidated or not.  There's also the issue of making sure 
this happens cluster-wide.  So instead, just do a simple timestamp check 
when the user is accessed.

Bill