Invalidating individual keys from rack-cache?

Question

Let's say a path on my rails app got stuck in rack cache. Is there a way to say: "/games/zelda" should be removed/invalidated from rack-cache?

Answer 1

Assumtions

1. Your rails app is named MyApp
2. the complete url you wish to purge is http://www.myapp.com/games/zelda

Step 1 obtain a normalized key

mock_request = Rack::MockRequest.env_for('/games/zelda', {"SERVER_NAME"=>"www.myapp.com"})
key = Rack::Cache::Key.call(Rack::Cache::Request.new(mock_request))

Step 2 retrieve storage objects

metastore_uri = MyApp::Application.config.action_dispatch.rack_cache[:metastore]
entitystore_uri = MyApp::Application.config.action_dispatch.rack_cache[:entitystore]

metastore = Rack::Cache::Storage.instance.resolve_metastore_uri(metastore_uri)
entitystore = Rack::Cache::Storage.instance.resolve_entitystore_uri(entitystore_uri)

Step 3 retrieve the metadata

stored_meta = metastore.read(key)

Step 4 purge the entity store for each compression type

stored_meta.each do |sm|
  entitystore.purge(sm[1]["X-Content-Digest"])
end

Step 5 purge the metastore

metastore.purge(key)

I hope this helps.

Answer 2

You can either delete one key or all keys from an Memcached instance. Unfortunately doesn't allow to list all keys. Therefore you cannot iterate over all keys and just delete the one you want to invalidate.

That said I see two options:

1. Delete all keys in Memcached.
2. Or change the path in the URI of your Memcached Storage config and re-cache all keys.