Fix RedisGrainDirectory uninitialize exception

[miguelhasse]

Updated the Uninitialize method to replace CloseAsync and synchronous Dispose calls with await _redis.DisposeAsync(), ensuring proper asynchronous disposal. Cleanup of _redis and _database fields is now handled in a finally block to guarantee resource release even if disposal fails.

This change is a fix to avoid NullReferenceException being thrown during calls to RedisGrainDirectory .Uninitialize

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Updates the Redis grain directory shutdown path to dispose the Redis connection asynchronously and ensure _redis/_database fields are cleared even if disposal throws, addressing a NullReferenceException during RedisGrainDirectory.Uninitialize.

Changes:

• Replace CloseAsync() + synchronous Dispose() with await _redis.DisposeAsync().
• Move cleanup of _redis and _database into a finally block to guarantee field cleanup.

[Copilot]

This change targets a shutdown-time exception path, but there’s no coverage ensuring Uninitialize is safe to call when initialization is partial/failed or when it’s invoked multiple times. Consider adding a Redis grain directory test which exercises the shutdown path (e.g., invoke Uninitialize via reflection or lifecycle and assert it doesn’t throw).

[ReubenBond]

What is the source of the NullReferenceException in this case, as in: what is null here? From your exception, it looks like it's null on line 199 (_redis.Dispose();). If that's the case, are there overlapping calls to Uninitialize that are setting _redis to null? If that's an issue (it might be, I'm not sure yet), then it would likely be good to guard against that in code (eg, capture _redis and set it to null atomically, possibly via an interlocked operation or using a lock statement)

[miguelhasse]

What is the source of the NullReferenceException in this case, as in: what is null here? From your exception, it looks like it's null on line 199 (_redis.Dispose();). If that's the case, are there overlapping calls to Uninitialize that are setting _redis to null? If that's an issue (it might be, I'm not sure yet), then it would likely be good to guard against that in code (eg, capture _redis and set it to null atomically, possibly via an interlocked operation or using a lock statement)

From the logged exception it look like it it thrown from inside StackExchange's implementation, but you may be right about the possible race condition. Using an interlocked operation might be a good idea.