#43 Log swallowed TryGetAsync exceptions

[matthewdevenny]

Closes #43.

Problem

NatsCache.TryGetAsync(string, IBufferWriter<byte>, …) caught all exceptions and returned false with no logging. A NATS connectivity error was indistinguishable from a normal cache miss and left no diagnostic trail.

What changed

TryGetAsync now logs a swallowed read failure, and the read path is reworked so each failure is logged exactly once.

• Log at Warning. A swallowed read failure means the cache genuinely failed (e.g. NATS down), not just missed — Debug would be invisible in production. Reuses the existing Exception event id (101). Still returns false, preserving the IBufferDistributedCache contract.
• Cancellation propagates. OperationCanceledException from a cancelled caller token is no longer swallowed into a false miss (and is not logged) — cooperative cancellation isn't a cache failure.
• No redundant logging. Exception logging moved out of the shared helpers (the lazy KV-store factory and GetAndRefreshAsync) up to the operation boundaries, so each failure is logged once:
  • Propagating ops (Get/Set/Refresh/Remove) → Error, then rethrow.
  • TryGetAsync swallow → Warning.
• Supporting mechanical changes: SetAsync resolves the store inside its logged try; the private remove helper is renamed RemoveCoreAsync to resolve an overload ambiguity when routing sync Remove through the logging public RemoveAsync.

Behavior notes

• Remove failures are now consistently logged at Error (a DeleteAsync failure was previously logged inconsistently or not at all).
• TryGetAsync now throws on caller cancellation instead of returning false — the idiomatic .NET behavior, and a deliberate change from the original "swallow everything" semantics.

Tests

New test/IntegrationTests/Cache/TryGetAsyncTests.cs, using an in-memory RecordingLogger<NatsCache> added to TestUtils (no new package dependency, so lock files are untouched):

1. TryGetAsync on a nonexistent bucket → returns false, writes nothing, logs exactly one Warning.
2. GetAsync on a nonexistent bucket → throws, logs exactly one Error (guards against the helpers double-logging).
3. TryGetAsync with a cancelled token → throws OperationCanceledException, no exception logged.

Verification

• Build clean with TreatWarningsAsErrors=true.
• Unit tests 62/62 (net8.0 + net10.0); integration tests 61/61.
• dotnet format --verify-no-changes passes.

Acceptance criteria

• ✅ A thrown error in the buffer read path produces a log entry.
• ✅ Return behavior is otherwise unchanged (still returns false on failure; cancellation now propagates by design).

[Copilot]

Pull request overview

This PR adds explicit logging for exceptions that are swallowed by NatsCache.TryGetAsync (to honor the IBufferDistributedCache “return false on failure” behavior) and introduces test utilities + an integration test to assert the behavior.

Changes:

• Add a dedicated debug log method (LogSwallowedException) and call it from TryGetAsync’s exception handler.
• Introduce an in-memory RecordingLogger<T> for capturing log entries in tests.
• Add an integration test that forces a read-path failure and asserts TryGetAsync returns false and logs the swallowed exception.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
test/TestUtils/Services/Logging/RecordingLogger.cs	Adds an in-memory test logger to capture ILogger calls for assertions.
test/IntegrationTests/Cache/TryGetAsyncTests.cs	Adds an integration test asserting swallowed exceptions are logged and TryGetAsync returns false.
src/NatsDistributedCache/NatsCache.Log.cs	Adds a new debug logging helper for swallowed exceptions.
src/NatsDistributedCache/NatsCache.cs	Updates TryGetAsync to log swallowed exceptions.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

[mtmk]

LGTM