[release/6.0] Store ApplicationServiceProvider in a WeakReference

[AndriySvyryd]

Fixes #27169

Description

In 6.0 we made a change to ServiceProviderCache to use instances of IDbContextOptions as keys for the internal ConcurrentDictionary. A key of type IDbContextOptions contains, among other things, the extension CoreOptionsExtension which has an ApplicationServiceProvider reference pointing to the service provider that was used to create the options.

After creation and disposal of the first DbContext the ServiceProviderCache keeps the IDbContextOptions incl. the (disposed) service provider scope, which still references all disposed scoped services, including the DbContext itself.

Customer impact

The first service provider scope per each DbContext type used in the application will never be garbage collected.

How found

Customer reported on 6.0.1

Regression

Yes. Regressed by #25313

Testing

Verified manually.

Risk

Low. This reverts the behavior to 5.0 wrt referencing ApplicationServiceProvider from ServiceProviderCache

[ajcvickers]

@AndriySvyryd Couldn't the IMemoryCache also cause the same issue?

[roji]

Is there a danger of the application service provider being collected too early under memory pressure, though it may still be needed? (I don't know this area too well)

Given that DbContextOptions is already immutable and that OptionsExtensions can be cloned, would it be simpler/safer to just put a cloned copy of DbContextOptions in the ConcurrentDictionary, where the service provider has been nulled out?

[ajcvickers]

Is there a danger of the application service provider being collected too early under memory pressure, though it may still be needed? (I don't this area too well)

No, because if anything else has a reference to it, then it won't be GC'ed. But if this is the only reference, then it can be GC'ed.

Given that DbContextOptions is already immutable and that OptionsExtensions can be cloned, would it be simpler/safer to just put a cloned copy of DbContextOptions in the ConcurrentDictionary, where the service provider has been nulled out?

I think it's worth exploring this.

[AndriySvyryd]

@AndriySvyryd Couldn't the IMemoryCache also cause the same issue?

We don't store services in IMemoryCache and since it's a singleton we don't support it being disposed.