[RedisCache] Allow injection of ConnectionMultiplexer

Currently the RedisCache creates the ConnectionMultiplexer and does not allow access to it. This prevents the application from reusing the ConnectionMultiplexer for other operations like PubSub.

Granted, the application could create another ConnectionMultiplexer, but the recommendation is to have only one per application.

I was thinking if it would be possible to have a separate constructor for RedisCache that would receive the ConnectionMultiplexer. I understand that so far Microsoft.Extensions.Caching.Redis did not leak any implementation details about its usage of StackExchange.Redis. However, I noticed that Microsoft.AspNetCore.DataProtection.Redis leaks StackExchange.Redis types here. So, I’m unclear about how you feel about keeping StackExchange.Redis as an implementation detail.

Proposed API

namespace Microsoft.Extensions.Caching.StackExchangeRedis
{
    public class RedisCacheOptions
    {
+       Func<IConnectionMultiplexer> ConnectionMultiplexerFactory { get; set; }     
    }

[davidfowl]

Yes we should allow for this. Not sure about injecting the IConnectionMultiplexer as a dependency though we should have an option that allows setting a Func<IConnectionMultiplexer>

[analogrelay]

I think that’s why there’s ConnectionMultiplexer.

Yep, I understand the purpose. Just trying to understand what issues you’re seeing with using two separate instances to help prioritize. Is there extra load in your system? (memory usage, cpu, etc.)

We’ll definitely be investigating this, but I just want to understand how this issue is negatively impacting applications right now in order to help us prioritize.