Annotations for invalidating cache entries on update

[bjarkih]

We add new runtime annotations that can be used to decorate methods that should write to or delete from the cache.

Technical details

Cachalot currently does not listen for explicit modifications to entries in the cache blocks it has under administration. The only updates to cache blocks are made upon expiry or overflow. This means that explicit modifications to cached objects are not immediately reflected in the cache.

Cache updates

We add a new CacheUpdate annotation that has the following parameters:

• name: Name of the cache block to modify (required).
• functional: Whether the method call should be treated as a function call.

With the functional flag set, CacheUpdate annotation can be used to decorate functions of the form f(x_1, ..., x_N) = y with the semantics of

assign cache entry (x_1, ..., x_N) a new value of y

The exact implementation of the functional annotation is determined as follows.

No return type

For a method void methodName(x_1, ..., x_N, y) with N + 1 arguments (N >= 0) annotated with CacheUpdate, the cache interceptor will proceed as follows:

• If N > 0 then we reset the cached entry determined by (x_1, ..., x_N).
• If N = 0 we reset the cached entry determined by y treating the function as f(y) = const.

A functional CacheUpdate on a method of the form void methodName() will clear the whole cache block.

Return type

For a method T methodName(x_1, ..., x_N) with N arguments (N >= 0) annotated with CacheUpdate, the cache interceptor will proceed as follows:

• If N > 0 then we reset the cached entry determined by (x_1, ..., x_N).
• If N = 0 we clear the whole cache block.

Cache removals

We add a new CacheDelete annotation that has the following parameters:

• name: Name of the cache block to modify (required).

For a method methodName(x_1, ..., x_N) with N arguments (N >= 0) annotated with CacheDelete, the cache interceptor will proceed as follows:

• If N > 0 then we reset the cached entry determined by (x_1, ..., x_N).
• If N = 0 we clear the whole cache block.

[bjarkih]

Thoughts on this @mrolafsson? Exact naming and implementation just a thought. In general we need a way to fine-grain control the cache lifecycle in this way.

[a-flammarion]

I am not clear how you update the cache?
You just reset it is that right? Which will force it to be updated the next time the call is made to retrieve the value?