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>
This commit is contained in:
Joseph Doherty
@@ -5,6 +5,7 @@ using System.Net.Sockets;
|
||||
using Mbproxy.Bcd;
|
||||
using Mbproxy.Options;
|
||||
using Mbproxy.Proxy;
|
||||
using Mbproxy.Proxy.Cache;
|
||||
using Mbproxy.Proxy.Multiplexing;
|
||||
using Microsoft.Extensions.Logging.Abstractions;
|
||||
using Shouldly;
|
||||
@@ -623,4 +624,136 @@ public sealed class PlcMultiplexerTests
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// ── Phase 12 Wave-1 regression tests ──────────────────────────────────────
|
||||
|
||||
/// <summary>
|
||||
/// W1.1 — verifies that <see cref="PlcMultiplexer.ReplaceContext"/> swaps the live
|
||||
/// per-PLC context on the running multiplexer, so the very next PDU's BCD rewriter
|
||||
/// uses the new tag map (not the captured-at-construction map). Before W1.1 this
|
||||
/// scenario would silently keep using the old map until the listener faulted and the
|
||||
/// supervisor's Polly loop reconstructed everything.
|
||||
/// </summary>
|
||||
[Fact]
|
||||
public async Task ReplaceContext_NewTagMap_VisibleOnNextPdu()
|
||||
{
|
||||
int backendPort = PickFreePort();
|
||||
await using var backend = new StubBackend(backendPort);
|
||||
backend.FcResponseFactory = (fc, _, _, txId) =>
|
||||
fc == 0x03 ? BuildFc03Response(txId, 1, 0x1234) : Array.Empty<byte>();
|
||||
|
||||
// Context 1 — tag at addr 100, BCD16. Wire 0x1234 decodes to decimal 1234.
|
||||
var ctx1 = MakeContext("PLC1", BcdTag.Create(100, 16));
|
||||
var plc = new PlcOptions { Name = "PLC1", ListenPort = 0, Host = "127.0.0.1", Port = backendPort };
|
||||
await using var mux = await BuildMuxAsync(plc, new ConnectionOptions(), ctx1);
|
||||
|
||||
var (client, pipe, listener, _) = await ConnectClientAsync(mux, plc.Name);
|
||||
try
|
||||
{
|
||||
// Read 1 with original ctx — wire 0x1234 should be decoded to 1234 (= 0x04D2).
|
||||
await client.SendAsync(BuildFc03ReadFrame(1, 100, 1), SocketFlags.None);
|
||||
var rsp1 = await ReadOneFrameAsync(client, TestContext.Current.CancellationToken);
|
||||
ushort decoded1 = (ushort)((rsp1[9] << 8) | rsp1[10]);
|
||||
decoded1.ShouldBe((ushort)1234, "with tag at 100, BCD wire 0x1234 must decode to decimal 1234");
|
||||
|
||||
// Swap to an empty tag map (counters preserved per the design's reseat contract).
|
||||
var ctx2 = new PerPlcContext
|
||||
{
|
||||
PlcName = "PLC1",
|
||||
TagMap = BcdTagMap.Empty,
|
||||
Counters = ctx1.Counters,
|
||||
Logger = NullLogger.Instance,
|
||||
};
|
||||
mux.ReplaceContext(ctx2);
|
||||
|
||||
// Read 2 with swapped ctx — no tag, raw 0x1234 must pass through unchanged.
|
||||
await client.SendAsync(BuildFc03ReadFrame(2, 100, 1), SocketFlags.None);
|
||||
var rsp2 = await ReadOneFrameAsync(client, TestContext.Current.CancellationToken);
|
||||
ushort raw2 = (ushort)((rsp2[9] << 8) | rsp2[10]);
|
||||
raw2.ShouldBe((ushort)0x1234,
|
||||
"after ReplaceContext to empty tag map, the next PDU must use the new map and pass 0x1234 through unchanged");
|
||||
}
|
||||
finally
|
||||
{
|
||||
client.Dispose();
|
||||
await pipe.DisposeAsync();
|
||||
listener.Stop();
|
||||
}
|
||||
}
|
||||
|
||||
/// <summary>
|
||||
/// W1.1 — verifies that swapping in a fresh response cache via <see cref="PlcMultiplexer.ReplaceContext"/>
|
||||
/// makes the running multiplexer consult the NEW cache for subsequent reads, not the
|
||||
/// old cache that was disposed by the supervisor. Without W1.1 the running mux would
|
||||
/// keep its constructor-captured cache reference and either return stale entries or
|
||||
/// hit a disposed cache.
|
||||
/// </summary>
|
||||
[Fact]
|
||||
public async Task ReplaceContext_NewCache_NextReadGoesToBackend_NotOldCache()
|
||||
{
|
||||
int backendPort = PickFreePort();
|
||||
await using var backend = new StubBackend(backendPort);
|
||||
backend.FcResponseFactory = (fc, _, _, txId) =>
|
||||
fc == 0x03 ? BuildFc03Response(txId, 1, (ushort)0x1111) : Array.Empty<byte>();
|
||||
|
||||
// Context 1 — cacheable tag at addr 200 with TTL 60_000 ms.
|
||||
var tag = new BcdTag(200, 16, CacheTtlMs: 60_000);
|
||||
var dict = new[] { tag }.ToDictionary(t => t.Address).ToFrozenDictionary();
|
||||
var map = new BcdTagMap(dict);
|
||||
var cache1 = new ResponseCache(maxEntriesPerPlc: 100, evictionIntervalMs: 5000);
|
||||
var ctx1 = new PerPlcContext
|
||||
{
|
||||
PlcName = "PLC1",
|
||||
TagMap = map,
|
||||
Counters = new ProxyCounters(),
|
||||
Logger = NullLogger.Instance,
|
||||
Cache = cache1,
|
||||
};
|
||||
|
||||
var plc = new PlcOptions { Name = "PLC1", ListenPort = 0, Host = "127.0.0.1", Port = backendPort };
|
||||
await using var mux = await BuildMuxAsync(plc, new ConnectionOptions(), ctx1);
|
||||
var (client, pipe, listener, _) = await ConnectClientAsync(mux, plc.Name);
|
||||
try
|
||||
{
|
||||
// Read 1 — populates cache1 from backend.
|
||||
await client.SendAsync(BuildFc03ReadFrame(1, 200, 1), SocketFlags.None);
|
||||
_ = await ReadOneFrameAsync(client, TestContext.Current.CancellationToken);
|
||||
await Task.Delay(50, TestContext.Current.CancellationToken);
|
||||
int afterFirst = backend.SeenProxyTxIds.Count;
|
||||
cache1.Count.ShouldBe(1, "cache1 must contain the first read");
|
||||
|
||||
// Read 2 — must hit cache1 (no backend traffic).
|
||||
await client.SendAsync(BuildFc03ReadFrame(2, 200, 1), SocketFlags.None);
|
||||
_ = await ReadOneFrameAsync(client, TestContext.Current.CancellationToken);
|
||||
backend.SeenProxyTxIds.Count.ShouldBe(afterFirst, "cache hit must not produce backend traffic");
|
||||
|
||||
// Swap in a brand-new (empty) cache via ReplaceContext.
|
||||
var cache2 = new ResponseCache(maxEntriesPerPlc: 100, evictionIntervalMs: 5000);
|
||||
var ctx2 = new PerPlcContext
|
||||
{
|
||||
PlcName = "PLC1",
|
||||
TagMap = map,
|
||||
Counters = ctx1.Counters,
|
||||
Logger = NullLogger.Instance,
|
||||
Cache = cache2,
|
||||
};
|
||||
mux.ReplaceContext(ctx2);
|
||||
|
||||
// Read 3 — old cache had the entry, but mux now uses cache2 which is empty,
|
||||
// so the next read MUST go to the backend.
|
||||
await client.SendAsync(BuildFc03ReadFrame(3, 200, 1), SocketFlags.None);
|
||||
_ = await ReadOneFrameAsync(client, TestContext.Current.CancellationToken);
|
||||
await Task.Delay(50, TestContext.Current.CancellationToken);
|
||||
backend.SeenProxyTxIds.Count.ShouldBe(afterFirst + 1,
|
||||
"after ReplaceContext, the running multiplexer must consult the NEW cache (empty) — not the old one (still warm)");
|
||||
cache2.Count.ShouldBe(1, "the new cache should be populated by the post-swap read");
|
||||
}
|
||||
finally
|
||||
{
|
||||
client.Dispose();
|
||||
await pipe.DisposeAsync();
|
||||
listener.Stop();
|
||||
cache1.Dispose();
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user