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Author SHA1 Message Date
Joseph Doherty 0868613890 mbproxy: add keepalive / connection monitoring 
The DL205/DL260 ECOM emits no TCP keepalives, so an idle backend socket
can be silently dropped by a middlebox (switch, firewall, NAT) after
2-5 minutes. Enable OS SO_KEEPALIVE on backend and accepted upstream
sockets, and drive a periodic synthetic FC03 heartbeat on each idle
backend socket so a dead path is detected before a real client request
hits it. Controlled by Connection.Keepalive (ON by default).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-15 09:40:54 -04:00
Joseph Doherty 1a2856526a mbproxy: strip historical phase/wave/plan references from source comments 
Comments described the *history* of how the code arrived (phase numbers,
wave IDs, review IDs, dated TODOs) instead of what it does today. That
scaffolding rotted as the codebase evolved. Cleaned 60 source files +
.gitignore; behaviour unchanged (387/387 tests still pass).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-14 13:04:30 -04:00
Joseph Doherty 9251c564c1 mbproxy: resolve remaining items from ReReviewAfterRemediation.md 
Closes the latent + minor + test-discipline items left after Wave 4. Updates
the re-review doc with a final resolution table — every actionable finding
now marked Resolved or Accepted with rationale.

NM3 — _supervisorCts leaks on re-Start
  StartAsync now disposes the previous CTS before reassigning. Idempotent:
  a try/catch (ObjectDisposedException) covers the very-first-Start case
  where the field-init CTS is still fresh.

NM4 — W2.15 TCS is single-shot
  _firstAttemptCompleted is no longer readonly; StartAsync re-creates it
  after the W2.16 guard so a re-Started supervisor's
  WaitForInitialBindAttemptAsync doesn't observe the previous run's signal.

Nm6 — _admin GetService<> returns null silently
  ProxyWorker.ExecuteAsync now logs a Warning when admin isn't registered.
  Preserves the loud-failure intent from the original IHostedService
  registration without forcing test hosts to wire admin.

Nm7 — AdminEndpointHost.DisposeAsync no double-dispose guard
  Added a volatile bool _disposed flag with an early-return at the top of
  DisposeAsync. Symmetry with PlcMultiplexer; protects against
  ProxyWorker.StopAsync explicitly disposing then DI disposing the singleton
  again on host shutdown.

T3 — RemoveInheritedAppsettings only fires on Build
  AfterTargets="Build;Publish" + a second Delete against $(PublishDir)
  so a `dotnet publish` against the test csproj doesn't ship the example
  PLCs from the linked install template.

T4 — Stale TryAttachOrCreate_*_ReturnsTrue_* test method names
  Renamed to AttachOrCreate_*_WasNew{True,False} after W3 dropped the bool
  return.

Accepted (with rationale documented in ReReviewAfterRemediation.md):
  Nm2 — CoalescedHit semantic is per-design
  Nm4 — _lastBindError preservation on clean exit is intentional forensics
  Nm5 — EventLogBridge has no injectable logger
  Nm8 — Cosmetic log noise
  T1  — Reflection on private fields documented as maintenance trap

Tests: 387 pass / 0 fail.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-14 07:02:21 -04:00
Joseph Doherty e66b17fe5f mbproxy: Wave 2 fixes from 2026-05-14 code review 
Resolves the 21 Major findings catalogued in
codereviews/2026-05-14/RemediationPlan.md (Wave 2). Tests: 370 pass / 0 fail
(baseline 363 + 7 new W2 regression tests).

Multiplexer / concurrency:
  W2.1  ConfigReconciler.Attach now threads the live coalescingAccessor through
        to add/restart-built supervisors so a hot-reload of
        ReadCoalescing.{Enabled,MaxParties} propagates to PLCs added or
        restarted via reload.
  W2.2  PlcMultiplexer._disposed and UpstreamPipe._disposed are now volatile
        for ARM/portability defense.
  W2.3  ProxyWorker._supervisors / ConfigReconciler._supervisors switched from
        Dictionary to ConcurrentDictionary; reconciler uses TryRemove. The
        outer Apply is serialised by a semaphore but the inner Add/Remove/
        Restart Task.WhenAll continuations run in parallel.
  W2.4  Counter parity for cache miss + coalescing-saturation miss documented
        inline (per-design contract; behavior unchanged).
  W2.5  _disposeCts.Dispose() and _connectGate.Dispose() guarded against late
        watchdog ticks.
  W2.6  _connectGate disposed in DisposeAsync.
  W2.7  Inline doc clarifying the post-rewriter FC byte read.

Cache / hot-reload:
  W2.8  PlcListenerSupervisor.ReplaceContextAsync now calls Clear() to capture
        the entry count, emits mbproxy.cache.flushed, then disposes the old
        cache. Previously the event was defined but never emitted.
  W2.9  Inline doc explaining the implicit "skip cache invalidation while
        recovering" gating (no backend reader during recovery → no FC06/FC16
        response → no invalidation).
  W2.10 ReloadValidator now re-checks resolved per-tag CacheTtlMs against
        Cache.AllowLongTtl after BcdTagMapBuilder folds the per-PLC default.

BCD rewriter:
  W2.11 Duplicate addresses detected within Global itself and within the per-PLC
        Add list itself, BEFORE the working dictionary collapses keys. Cross-list
        collisions (Global vs Add) remain the documented width-override pattern.
        Previously the DuplicateAddress error was unreachable dead code.
  W2.12 OverlappingHighRegister reports each colliding pair exactly once
        (canonicalised low/high pair tracked in a HashSet).
  W2.13 FC16 32-bit write rejects clientLow > 9999 or clientHigh > 9999 BEFORE
        the high*10000+low reconstruction. Without this guard, (high=9999,
        low=9999) silently re-encoded as (high=9998, low=9999), losing 1 from
        the high word.
  W2.14 FC16 validates pdu.Length >= 6 + qty*2 upfront — no half-rewritten
        requests when a malformed client claims more registers than it ships.

Supervisor:
  W2.15 WaitForInitialBindAttemptAsync now backed by TaskCompletionSource
        instead of 10ms busy-poll. Resolves race against fast Stopped→Bound→
        Stopped transitions and hangs when the supervisor task throws.
  W2.16 StartAsync refuses re-entry on a non-Stopped supervisor (was leaking
        the previous _supervisorCts).
  W2.17 New TransitionTo helper writes _state, _lastBindError, and (optionally)
        _recoveryAttempts under one lock. Snapshot() reads under the same lock
        so the status page never reports an inconsistent triple. Truncate
        helper extracted (was copy-pasted across three sites).
  W2.18 MbproxyOptionsValidator + ReloadValidator reject Connection.{Backend
        ConnectTimeoutMs, BackendRequestTimeoutMs, GracefulShutdownTimeoutMs}
        <= 0. Misconfigured 0 produces immediate CancelAfter(0) failures.

Hosting / diagnostics:
  W2.20 ProxyWorker.StopAsync supervisor-stop deadline now reads from
        IOptionsMonitor.CurrentValue.Connection.GracefulShutdownTimeoutMs
        (was hard-coded 5s).
  W2.21 src/Mbproxy/appsettings.json deleted; the published file is now a Link
        to install/mbproxy.config.template.json so the binary ships with a
        usable, fully-commented example config instead of an empty stub. Tests
        strip the inherited file from their bin via an AfterTargets="Build"
        Target so they don't pick up the template's example PLCs.
  W2.22 invalidBcdWarnings (PlcPdusStatus) and codeOther (ExceptionCounts)
        added to StatusDto, plumbed through StatusSnapshotBuilder, surfaced
        in StatusHtmlRenderer table cells.
  W2.23 EventLogBridge caches EventLog.SourceExists at construction so Emit
        doesn't hit the registry on every Error+ log line.

New regression tests:
  ReloadValidatorTests:
    Validate_PerTagCacheTtl_Above60s_Without_AllowLongTtl_Fails
    Validate_PerTagCacheTtl_Above60s_With_AllowLongTtl_Passes
    Validate_ResolvedTtl_FromPerPlcDefault_AboveCap_Fails
    Validate_ZeroBackendConnectTimeoutMs_Fails
    Validate_NegativeGracefulShutdownTimeoutMs_Fails
  BcdPduPipelineTests:
    FC16_32Bit_ClientHighOrLowAbove9999_PassesThroughRaw_WithInvalidBcdWarning
    FC16_TruncatedRegisterData_PassesThroughRaw_NoPartialRewrite

Reworked tests in BcdTagMapBuilderTests for the W2.11 contract (Global dup,
Add dup, Add-overrides-Global accepted as width override).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-14 05:48:44 -04:00
Joseph Doherty ce32c5cee8 mbproxy: Wave 1 fixes from 2026-05-14 code review 
Resolves the four critical correctness defects + the ShutdownCoordinator
double-stop ordering bug called out in codereviews/2026-05-14/Overview.md.
Tests: 362 pass / 0 fail (baseline 358 + 4 new W1 regression tests).

W1.1 — Context swap on running multiplexer.
  PlcMultiplexer._ctx becomes volatile with a new ReplaceContext() method
  that re-registers the cache stats provider on the (preserved) counters.
  PlcListener exposes its multiplexer; PlcListenerSupervisor.ReplaceContextAsync
  swaps the running mux first, then disposes the old cache. Hot-reload
  tag-list changes and the cache-flush-on-reload contract now actually take
  effect on the next PDU instead of waiting for the next listener fault.

W1.2 — Coalescing factory leak.
  When the InFlightByKey factory soft-fails (allocator saturation or duplicate
  TxId), the cleanup path now TryRemoves the stub and walks every party on it
  (including late attachers) to deliver Modbus exception 0x04. Previously
  only the leader got the exception; late attachers waited forever for a
  response that no backend round-trip would ever fire.

W1.3 — Backend-reader head-of-line block.
  UpstreamPipe gains TrySendResponse for non-blocking enqueue. The per-PLC
  backend reader's fan-out loop uses it instead of awaiting SendResponseAsync,
  so a wedged upstream's full bounded response channel can no longer stall
  the single backend reader and starve every other client on that PLC. New
  responseDropForFullUpstream counter on ProxyCounters / CounterSnapshot
  records the drops.

W1.4 — Stranded outbound frames after cascade.
  TearDownBackendAsync acquires _connectGate and drains any frames left in
  _outboundChannel after the writer task faulted/cancelled, releasing their
  proxy TxIds back to the allocator. Without this, a fresh
  EnsureBackendConnectedAsync racing the cascade would send stranded frames
  with old TxIds onto the new backend socket; the responses would arrive
  with no correlation entry and the upstream peers would hang on the
  watchdog until BackendRequestTimeoutMs.

W1.5 — Delete ShutdownCoordinator (Option B).
  Drain logic moved into ProxyWorker.StopAsync. AdminEndpointHost is no
  longer registered as IHostedService; ProxyWorker drives its lifecycle
  directly so admin starts after listeners are bound and stops AFTER the
  in-flight drain (the design's documented contract). Admin is resolved
  lazily in ExecuteAsync to break the circular DI graph
  (Admin -> StatusSnapshotBuilder -> ProxyWorker). GracefulShutdownTimeoutMs
  is now read fresh from IOptionsMonitor.CurrentValue at stop time, so a
  hot-reloaded value is honoured. Removes ShutdownCoordinator + tests.

New tests:
  PlcMultiplexerTests.ReplaceContext_NewTagMap_VisibleOnNextPdu
  PlcMultiplexerTests.ReplaceContext_NewCache_NextReadGoesToBackend_NotOldCache
  UpstreamPipeTests.TrySendResponse_WhenChannelFull_ReturnsFalse_WithoutBlocking
  UpstreamPipeTests.TrySendResponse_AfterDispose_ReturnsFalse

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-14 05:16:13 -04:00
Joseph Doherty 1db900edef mbproxy: add opt-in response cache (Phase 11) 
Layers a per-PLC, per-tag response cache on top of Phase 10's coalescing.
Cache is OFF by default per tag (CacheTtlMs = 0); a fresh deployment with no
TTL config behaves identically to Phase 10. Operators opt tags in by setting
CacheTtlMs > 0 on a BcdTagOptions entry (or DefaultCacheTtlMs > 0 on a
PlcOptions entry), explicitly acknowledging the staleness window.

Cache lookup order: cache -> coalesce -> backend. A cache hit short-circuits
both Phase 10's coalescing path and Phase 9's backend send. Cache stores
POST-rewriter PDU bytes so hits never re-invoke the BCD rewriter. FC06/FC16
write responses invalidate every cached entry whose address range overlaps
the write (half-open interval math).

New types (Mbproxy.Proxy.Cache, all internal):
- CacheKey (record-struct, same shape as CoalescingKey but kept SEPARATE so
  the two phases evolve independently).
- CacheEntry, ResponseCache (IDisposable; LRU + PeriodicTimer eviction
  loop), CacheInvalidator (pure overlap matcher), CacheLogEvents (stable
  mbproxy.cache.* names).

Multi-tag range TTL = min(TTLs); any tag with TTL = 0 in the range disables
caching for the whole read (conservative-by-design).

Options surface:
- BcdTagOptions.CacheTtlMs (nullable int; null = fall through to PLC default)
- PlcOptions.DefaultCacheTtlMs
- MbproxyOptions.Cache.{AllowLongTtl, MaxEntriesPerPlc, EvictionIntervalMs}
- TTL > 60_000 ms requires Cache.AllowLongTtl = true (reload validation).

Admin counters (Tier 1.8 + Tier 2 cache-memory KPIs from docs/kpi.md):
- CacheHitCount, CacheMissCount, CacheInvalidations on ProxyCounters.
- CacheEntryCount, CacheBytes via a new ICacheStatsProvider snapshot path.
- /status.json and the HTML page surface a new Cache cell per PLC row.

Hot-reload: any tag-list change to a PLC reseats the per-PLC context with a
fresh cache; the old cache is disposed inside ReplaceContextAsync. Per-tag
flush granularity is intentionally not implemented in v1.

PLCs with no cache-eligible tags (every resolved tag has CacheTtlMs = 0)
get Cache = null on the context and skip the eviction timer entirely, so
the no-cache path is byte-identical to Phase 10.

Tests (32 new unit + 5 new E2E = 37 new; suite now 314 unit + 48 E2E):
- CacheKeyTests, CacheEntryTests (records + boundary semantics).
- CacheInvalidatorTests: full overlap, both partials, adjacent-not-
  overlapping, disjoint, different unit ID + auxiliary FC-filter / zero-qty.
- ResponseCacheTests: round-trip, lazy expiry, range invalidation,
  unit-id filter, LRU bound, LRU access tracking, concurrent get/set,
  dispose, clear, approximate-bytes accounting.
- ResponseCacheMultiplexerTests (stub-backend): hit short-circuits
  coalescing, BCD-decoded bytes are cached not raw, FC06 invalidates
  overlapping, non-overlapping write does not invalidate, multi-tag
  TTL=min rule, regression-cache-disabled-by-default-is-Phase-10, hit
  works even when backend unreachable.
- ResponseCacheE2ETests (pymodbus DL205 sim, sequential reads):
  * Headline: 10 reads with TTL=1000 ms -> 9 hits, 1 miss, 1 backend trip.
  * TTL expiry path with sleep > TTL.
  * Write invalidation through the proxy on a scratch register.
  * BCD-decoded bytes are cached, not raw BCD nibbles.
  * Regression: Cache disabled by default -> behaviour byte-identical to
    Phase 10.

Pre-existing flake hardened: BackendDisconnect_CascadesToAllUpstreams now
polls briefly for the cascade counter to absorb the inherent scheduling
gap between "upstream EOF observed" and "counter incremented inside
TearDownBackendAsync." Counter semantics unchanged.

Phase doc updated with implementation clarifications discovered during
this work (CacheKey kept separate from CoalescingKey, LastUsedTick is
long, FC06/FC16 startAddr/qty parsing extension, cache-pre-connect
short-circuit, write-invalidation only on successful responses).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-14 03:08:51 -04:00
Joseph Doherty a2dba4bd07 mbproxy: add in-flight read coalescing (Phase 10) 
When two or more upstream clients send the same FC03/FC04 read while a
matching request is already in flight on the same PLC's multiplexed
backend socket, attach the late arrivals to the existing InFlightRequest
.InterestedParties list instead of opening a second backend round-trip.
The single backend response fans out to every attached party with each
party's original MBAP TxId restored individually. Zero post-response
staleness — coalescing operates entirely within the in-flight window
(microseconds to ~10 ms typical); the proxy is NOT a cache layer.

Headline mechanism:

- New record struct CoalescingKey(UnitId, Fc, StartAddress, Qty) keys
  the per-PLC InFlightByKeyMap. FC03 and FC04 are separate Modbus
  tables and never share a key; different unit IDs never coalesce;
  writes (FC06/FC16) bypass the coalescing path entirely.
- InFlightByKeyMap uses a simple lock around a Dictionary; atomic
  TryAttachOrCreate either appends a new party to the in-flight
  request's mutable List<InterestedParty> or invokes a factory to
  build a fresh entry. Per-entry MaxParties cap (default 32) bounds
  fan-out cost; past the cap, the next arrival opens a new entry.
- PlcMultiplexer.OnUpstreamFrameAsync takes the coalescing path for
  FC03/FC04 when Mbproxy.Resilience.ReadCoalescing.Enabled. The
  factory closure does the Phase-9 work (allocate TxId, add to
  CorrelationMap); the channel send happens AFTER returning from
  TryAttachOrCreate so the map lock is not held across the async send.
- Response fan-out in RunBackendReaderAsync removes the entry from
  InFlightByKeyMap before iterating InterestedParties, ensuring no
  concurrent attach can mutate the list during iteration.
- Cascade + watchdog paths also drain the key map so a stale entry
  cannot outlive its backend round-trip.

Counter accounting balance (per snapshot): CoalescedHitCount +
CoalescedMissCount equals total FC03 + FC04 requests since startup.
Even with coalescing disabled, every read still bumps Miss so dashboard
math stays balanced.

New surface (additive only):
- src/Mbproxy/Proxy/Multiplexing/CoalescingKey.cs
- src/Mbproxy/Proxy/Multiplexing/InFlightByKeyMap.cs
- src/Mbproxy/Proxy/Multiplexing/CoalescingLogEvents.cs
- ReadCoalescingOptions on ResilienceOptions
- CoalescedHitCount / CoalescedMissCount /
  CoalescedResponseToDeadUpstream counters surfaced on /status.json
  per PLC and as a compact "Coal" cell on the HTML status page.

Phase 9 test patch: TwoUpstreams_ProxyTxIds_AreDistinct_OnTheWire
previously read the same register from both clients (which now
coalesces). Patched to read two different addresses so the test still
proves distinct backend TxIds without violating the coalescing
contract.

Tests added: 24 new (19 unit + 5 E2E):
- CoalescingKeyTests (5)
- InFlightByKeyMapTests (6, includes concurrent stress)
- ReadCoalescingTests (8, stub-backend with deterministic delay)
- ReadCoalescingE2ETests (5, pymodbus simulator; coalescing-active
  during overlap is proven against the stub, not the sim, due to
  pymodbus 3.13's known concurrent-frame bug)

Total: 325 tests passing (282 unit + 43 E2E).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-14 02:26:06 -04:00
Joseph Doherty 56eee3c563 mbproxy: initial commit through Phase 9 (TxId multiplexing) 
Adds the mbproxy service end-to-end. Phases 00-08 implement the
production-ready single-listener / 1:1-backend transparent Modbus TCP
proxy with bidirectional BCD rewriting for the ~54-PLC DL205/DL260
fleet. Phase 9 replaces the connection layer with a single backend
socket per PLC plus MBAP TxId rewriting, lifting the H2-ECOM100's
4-concurrent-client cap as an operational ceiling.

Phase 9 additions of note:
- PlcMultiplexer + UpstreamPipe + TxIdAllocator + CorrelationMap
- InFlightRequest with IReadOnlyList<InterestedParty> (load-bearing
  for Phase 10 read coalescing — do not collapse to a single field)
- Per-request watchdog: surfaces Modbus exception 0x0B to upstream
  on BackendRequestTimeoutMs, defending against lost responses,
  dead-PLC paths, and pymodbus 3.13.0's concurrent-multiplexed-
  request bug (its ServerRequestHandler.last_pdu state race)
- Status DTO + HTML gain inFlight / maxInFlight / txIdWraps /
  disconnectCascades / queueDepth (Tier 1.6 in docs/kpi.md)

Tests: 263 unit + 38 E2E. Multiplexer correctness under truly
concurrent backend traffic is proved against a stub backend in
PlcMultiplexerTests; MultiplexerE2ETests paces requests so pymodbus
3.13's single-PDU framer stays in known-good mode.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
 2026-05-14 01:49:35 -04:00