Asp.Net core distributed caching

Question

I am currently using MemoryCache _cache = new MemoryCache(new MemoryCacheOptions()); for caching some data from database that does not change so often, but it does change. And on create/update/delete of that data I do the refresh of the cache.

This works fine, but the problem is that on production we will have few nodes, so when method for creating of record is called for instance, cache will be refreshed only on that node, not on other nodes, and they will have stale data.

My question is, can I somehow fix this using MemoryCache, or I need to do something else, and if I do, what are the possible solutions?

Answer 1

I think you are looking for is Distributed Caching

Using the IDistributedCache interface you can use either Redis or Sql Server and it supplies basic Get/Set/Remove methods. Changes made on one node will be available to other nodes.

Using Redis is a great way of sharing Session type data between servers in a load balanced environment, Sql Server does not seem to be a great fit given that you seem to be caching to avoid db calls.

It might also be worth considering if you are actually complicating things by caching in the first place. When you have a single application you see the benefit, as keeping them in application memory saves a request over the network, but when you have a load balanced scenario, you have to compare retrieving those records from a distributed cached vs retrieving them from the database.

If the data is just an in memory copy of a relatively small database table, then there is probably not a lot to choose performance wise between the two. If the data is based on a complicated expensive query then the cache is the way to go.

If you are making hundreds of requests a minute for the data, then any network request may be too much, but you can consider what are the consequences of the data being a little stale? For example, if you update a record, and the new record is not available immediately on every server, does your application break? Or does the change just occur in a more phased way? In that case you could keep your in process memory cache, just use a shorter Time To Live.

If you really need every change to propagate to every node straight away then you could consider using a library like Cache Manager in conjunction with Redis which can combine an in memory cache and synchronisation with a remote cache.

Answer 2

Somewhat dated question, but maybe still useful: I agree with what ste-fu said, well explained.

I'll only add that, on top of CacheManager, you may want to take a look at FusionCache ⚡ , which I recently released.

On top of supporting an optional distributed 2nd layer transparently managed for you, it also has some other nice features like an optimization that prevents multiple concurrent factory for the same cache key from being executed (less load on the source database), a fail-safe mechanism and advanced timeouts with background factory completion

If you will give it a chance please let me know what you think.

/shameless-plug