Microsoft.Extensions.Caching.StackExchangeRedis 9.0.3 - when using HybridCache RedisCacheImpl.IsHybridCacheDefined causes infinite recursion

[xeonix]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Hello guys.
Today I updated all my NuGets and my .NET 9 Back-End hanged.
I'm using the following NuGets to do the caching stuff in my project:
Microsoft.Extensions.Caching.Hybrid 9.3.0
Microsoft.Extensions.Caching.StackExchangeRedis 9.0.3
After investigating the issue and inspecting this GitHub repository I've find out what's happening:
I registered HybridCache like this:

services.AddHybridCache(options =>
        {
            options.DefaultEntryOptions = new HybridCacheEntryOptions
            {
                Expiration = TimeSpan.FromMinutes(5),
                LocalCacheExpiration = TimeSpan.FromMinutes(2.5)
            };
        });

and then added some RedisCache like this:

services.AddStackExchangeRedisCache(options =>
{
    options.Configuration = redisCacheConnectionString;
    options.InstanceName = redisCacheKeyPrefix;
});

The problem here is with IsHybridCacheDefined method:

internal sealed class RedisCacheImpl : RedisCache
{
    public RedisCacheImpl(IOptions<RedisCacheOptions> optionsAccessor, ILogger<RedisCache> logger, IServiceProvider services)
        : base(optionsAccessor, logger)
    {
        HybridCacheActive = IsHybridCacheDefined(services);
    }

    public RedisCacheImpl(IOptions<RedisCacheOptions> optionsAccessor, IServiceProvider services)
        : base(optionsAccessor)
    {
        HybridCacheActive = IsHybridCacheDefined(services);
    }

    // HybridCache optionally uses IDistributedCache; if we're here, then *we are* the DC
    private static bool IsHybridCacheDefined(IServiceProvider services)
        => services.GetService<HybridCache>() is not null;
}

When it resolves HybridCache which then resolves IDistributedCache.
According to StackExchangeRedisCacheServiceCollectionExtensions, RedisCacheImpl is registered as:

services.Add(ServiceDescriptor.Singleton<IDistributedCache, RedisCacheImpl>());

So when resolving IDistributedCache and instantiating RedisCacheImpl, it's ctor calls IsHybridCacheDefined method, which resolves HybridCache, which resolves IDistributedCache resulting into an infinite resolution loop.
With Microsoft.Extensions.Caching.StackExchangeRedis 9.0.2 - RedisCacheImpl has no IsHybridCacheDefined method, so everything works fine.

Expected Behavior

No response

Steps To Reproduce

1. When configuring DI - call services.AddHybridCache, then services.AddStackExchangeRedisCache
2. Try to resolve HybridCache anywhere (i.e. Controller/Minimal API)

Exceptions (if any)

No response

.NET Version

9.0.201

Anything else?

No response

[milkyjoe90]

I have also experienced exactly the same issue with HybridCache and Redis

[EsgAtWorkleap]

FYI this also happens with the 9.2.0 preview of Microsoft.Extensions.Caching.Hybrid. As soon as we update Microsoft.Extensions.Caching.StackExchangeRedis to 9.0.3, we get the issue

[xeonix]

@EsgAtWorkleap Yes, because the problem is with Microsoft.Extensions.Caching.StackExchangeRedis 9.0.3 only.
After updating all NuGets I rolled back everything and started updating them one by one to find the problematic one.

[mgravell]

Investigating as a priority; some weird DI interplay - will get to the bottom of it. I have checked, and I'm certain that the only change in 9.0.3 is this metadata discovery, so it should be entirely safe and reasonable to use 9.0.2 as a workaround for now, and: any fix is going to be to Microsoft.Extensions.Caching.StackExchangeRedis:

- <PackageReference Include="Microsoft.Extensions.Caching.StackExchangeRedis" Version="9.0.3" />
+ <PackageReference Include="Microsoft.Extensions.Caching.StackExchangeRedis" Version="9.0.2" />

[mgravell]

Huge apologies. Fix PR is #60915 (main) and #60916 (backport to 9.x). I'm going to see if I can get 9.0.3 unlisted.

Can I still use HybridCache

Yes: just avoid 9.0.3 of Microsoft.Extensions.Caching.StackExchangeRedis - 9.0.2 is fine, or if you're reading in the future: something >= 9.0.4

Not trying to make excuses here - this was just a stupid and (with hindsight) avoidable error. Both pieces unit tested absolutely fine in isolation, *sigh*. The following is purely for education to stop anyone else making the same mistake, and isn't me trying to dodge accountability:

• three related components in three different repos - abstractions (runtime), aspnet-cache (aspnetcore) and the cache implementation (extensions)
• the two non-trivial bits can't directly reference each-other, so a fake was used to prove the handshake
• the fake did not have the real DI signature, but was left very ... well, fake (trivial .ctor etc)
• the "real" versions, however, were such that the concrete HybridCache was asking about IDistributedCache and the concrete IDistributedCache was asking questions about HybridCache; this made the CI spin indefinitely

The fix is simple: at least one of the two should defer asking questions until after it has been constructed

The moral / learning point: if you're going to fake your DI: don't make it too fake

Side note: I wonder if the DI could do a better job of detecting stack dives. In an ideal world, the DI would also have a "do you have a service registration for X?" API that doesn't actually force X to be manifested!

[mgravell]

Microsoft.Extensions.Caching.StackExchangeRedis 9.0.3 has been delisted - the underlying fixes will be applied presumably for 9.0.4, but until then: HybridCache works fine with 9.0.2 (indeed, the entire point of IDistributedCache is that HybridCache doesn't know what the backend is).

[milkyjoe90]

Thanks so much for jumping on this so quickly @mgravell!