Dynamic entry ttl.

[ruseinov]

I'm building a daemon that needs to cache entries with TTL based on a configuration parameter.

The current approach is as follows:

#[once(time = 2, result = true, sync_writes = true)]
async fn estimate_fees() -> Result

This means that the TTL can only be specified once per function. What would be nice is the ability to specify the TTL dynamically.

Some options:
a. Based on function params: async fn estimate_fees(ttl: Duration, other_params..), that could be configured similar to key generation.
b. Perhaps a memoized method could be defined within a body of another method, which would then pass the ttl param

fn some_method(config: Config) {

define_cache! {
  CACHE;
  cache_ttl = config.ttl
  sync_writes = true
  result = true
  async fn estimate_fees() -> Result
}

}

Or even a more manual implementation, as long as it provides quick read-only functionality and synchronized writes (to do the init only once per TTL, since this is quite an expensive operation).

[omid]

It's possible in my fork: https://github.com/omid/kash