854c3bcfec
Closes Stream D per docs/v2/implementation/phase-6-1-resilience-and-observability.md. New Configuration.LocalCache types (alongside the existing single-file LiteDbConfigCache): - GenerationSealedCache — file-per-generation sealed snapshots per decision #148. Each SealAsync writes <cache-root>/<clusterId>/<generationId>.db as a read-only LiteDB file, then atomically publishes the CURRENT pointer via temp-file + File.Replace. Prior-generation files stay on disk for audit. Mixed-generation reads are structurally impossible: ReadCurrentAsync opens the single file named by CURRENT. Corruption of the pointer or the sealed file raises GenerationCacheUnavailableException — fails closed, never falls back silently to an older generation. TryGetCurrentGenerationId returns the pointer value or null for diagnostics. - StaleConfigFlag — thread-safe (Volatile.Read/Write) bool. MarkStale when a read fell back to the cache; MarkFresh when a central-DB read succeeded. Surfaced on /healthz body and Admin /hosts (Stream C wiring already in place). - ResilientConfigReader — wraps a central-DB fetch function with the Stream D.2 pipeline: timeout 2 s → retry N× jittered (skipped when retryCount=0) → fallback to the sealed cache. Toggles StaleConfigFlag per outcome. Read path only — the write path is expected to bypass this wrapper and fail hard on DB outage so inconsistent writes never land. Cancellation passes through and is NOT retried. Configuration.csproj: - Polly.Core 8.6.6 + Microsoft.Extensions.Logging.Abstractions added. Tests (17 new, all pass): - GenerationSealedCacheTests (10): first-boot-no-snapshot throws GenerationCacheUnavailableException (D.4 scenario C), seal-then-read round trip, sealed file is ReadOnly on disk, pointer advances to latest, prior generation file preserved, corrupt sealed file fails closed, missing sealed file fails closed, corrupt pointer fails closed (D.4 scenario B), same generation sealed twice is idempotent, independent clusters don't interfere. - ResilientConfigReaderTests (4): central-DB success returns value + marks fresh; central-DB failure exhausts retries + falls back to cache + marks stale (D.4 scenario A); central-DB + cache both unavailable throws; cancellation not retried. - StaleConfigFlagTests (3): default is fresh; toggles; concurrent writes converge. Full solution dotnet test: 1033 passing (baseline 906, +127 net across Phase 6.1 Streams A/B/C/D). Pre-existing Client.CLI Subscribe flake unchanged. Integration into Configuration read paths (DriverInstance enumeration, LdapGroupRoleMapping fetches, etc.) + the sp_PublishGeneration hook that writes sealed files lands in the Phase 6.1 Stream E / Admin-refresh PR where the DB integration surfaces are already touched. Existing LiteDbConfigCache continues serving its single-file role for the NodeBootstrap path. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
21 lines
917 B
C#
21 lines
917 B
C#
namespace ZB.MOM.WW.OtOpcUa.Configuration.LocalCache;
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/// <summary>
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/// Thread-safe <c>UsingStaleConfig</c> signal per Phase 6.1 Stream D.3. Flips true whenever
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/// a read falls back to a sealed cache snapshot; flips false on the next successful central-DB
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/// round-trip. Surfaced on <c>/healthz</c> body and on the Admin <c>/hosts</c> page.
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/// </summary>
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public sealed class StaleConfigFlag
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{
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private int _stale;
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/// <summary>True when the last config read was served from the sealed cache, not the central DB.</summary>
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public bool IsStale => Volatile.Read(ref _stale) != 0;
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/// <summary>Mark the current config as stale (a read fell back to the cache).</summary>
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public void MarkStale() => Volatile.Write(ref _stale, 1);
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/// <summary>Mark the current config as fresh (a central-DB read succeeded).</summary>
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public void MarkFresh() => Volatile.Write(ref _stale, 0);
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}
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