Selecting cache key starting with something?

[dotnetshadow]

Great library,

I was wondering is there a way to remove cache key based on a selector such as remove all keys starting with "product-id-" ?

As similar question was asked here:
#6

Looking for something like below, but for .net core

 {
            var cacheKeys = _cachingService.ObjectCache.Where(kvp => kvp.Key.Equals("MyCacheKey"))
                .Select(kvp => kvp.Key);
            foreach (var cacheKey in cacheKeys)
            {
                _cachingService.ObjectCache.Remove(cacheKey);
            }
        }

Also is the a feature where a cache object can be dependent on another cache object.
i.e. Cache A has a dependency on Cache B (when it's cleared), I would like cache a to be cleared too

[alastairtree]

The simple answer is that key iteration is blocked on the new version of MemoryCache, the underlying Microsoft library LazyCache builds on top of, so LazyCache cannot easily give you a built-in way to solve it. Blocking iteration on all the keys is sensible for performance and concurrency reasons. This is a breaking change in the upgrade from 0.7 to 2.0.

To solve your requirement I can think of two ways:

1. Use a separate instance of CachingService everywhere you need to use keys product-id- and have this use a separate provider which you can then dispose and recreate to clear the "product cache" separate from the main cache:

IAppCache productCache = new CachingService(new MemoryCacheProvider(new MemoryCache(new MemoryCacheOptions())));

// do some caching

// and then later on when you want to clear it - dispose and recreate
productCache.CacheProvider.Dispose();
productCache = new CachingService(new MemoryCacheProvider(new MemoryCache(new MemoryCacheOptions())));

2. Alternatively you could cache the relationship between the keys (and so have a type of cache regions feature), using a cached list of keys to allow you retrieve all dependent cache keys. This stack overflow post has a good example. You might then want to wrap the logic to add something to a cache dependency list, or to remove all inside that list, in extension method to make it more re-usable.

Does this allow you to work around the change?

[dotnetshadow]

@alastairtree Cheers thanks for that, I actually ended up going for the second version which does the job for now. I like the suggestion to have a wrapper with extension methods.

Maybe if other people require this functionality it might be worth looking into making it a feature for your library

[agrath]

#86 Has a pull request maintaining an internal cache key list

[alastairtree]

This is a very similar to #74 and I have added a workaround to clearing a range of items using cancellation tokens as a comment there which may be useful to folks who find this ticket.