Replace cache lockers with production-ready sp_getapplock and SETNX implementations#4
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… lockers SQL Server now uses sp_getapplock/sp_releaseapplock for true atomic session-level locking, eliminating the non-atomic check-then-set race condition in the old DistributedCacheLocker. Redis now uses SET NX PX + compare-and-delete Lua scripts for atomic distributed locking. Memory cache drops the unnecessary SemaphoreSlimLocker since IMemoryCache reference semantics and ConcurrentDictionary already guarantee thread safety. Also fixes a bug in IMemoryCacheExtensions.SetKey where the namespace tracking entry was written to the wrong cache key (individual key instead of namespace).
…ic via Lua scripts
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Summary
DistributedCacheLocker(check-then-set race condition) with backend-specific lockers:SqlServerCacheLocker(sp_getapplock) andRedisCacheLocker(SET NX PX + compare-and-delete Lua scripts)SemaphoreSlimLockerfrom the memory cache —IMemoryCachereference semantics andConcurrentDictionaryalready guarantee thread safetyIMemoryCacheExtensions.SetKeywhere the namespace tracking entry was written under the wrong cache key (individual key instead of the namespace key), preventing expiration options from ever being applied to the tracking dictChanges
SqlServerCacheLocker: singlesp_getapplockcall with native SQL Server blocking up toLockTimeout; released viasp_releaseapplockon a heldSqlConnectionRedisCacheLocker: atomicSET NX PXacquire + compare-and-delete release, both single Lua scripts; polls every 100 ms up toLockTimeoutNullCacheLock.IsAcquirednow initializes totrue(wasfalse, silently skipping everyWaitForLockThenAsynccallback when used withNullCacheLocker)MemoryActionCache→NullCacheLock/NullCacheLocker;SqlServerActionCacheFactorynow injectsIOptions<SqlServerCacheOptions>to extract the connection stringDistributedCacheLocker,DistributedCacheLock,SemaphoreSlimLocker,SemaphoreSlimLockTest plan
SqlServerCacheLockerrequires a live SQL Server instance to test locking behaviour end-to-end (covered by integration tests against a real DB)