fix(focas): per-device connect-attempt backoff across the three loops (05/STAB-8)

2026-07-13 12:16:31 -04:00
parent 962afed241
commit e54af9b948
3 changed files with 118 additions and 3 deletions
@@ -0,0 +1,86 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.FOCAS;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests;
+
+/// <summary>
+///     05/STAB-8 — a dead FOCAS CNC must not pay a full two-socket reconnect on every tick of each
+///     read / probe / fixed-tree / recycle loop. The per-device <see cref="ConnectionBackoff"/>
+///     gates the connect path; the probe bypasses it and a successful connect resets it. No FOCAS
+///     fixture exists — the fake-client suite is authoritative.
+/// </summary>
+[Trait("Category", "Unit")]
+public sealed class FocasConnectBackoffTests
+{
+    private static FocasDriverOptions Options(bool probeEnabled) => new()
+    {
+        Devices = [new FocasDeviceOptions("focas://10.0.0.5:8193")],
+        Tags = [new FocasTagDefinition("R", "focas://10.0.0.5:8193", "R100", FocasDataType.Byte)],
+        Probe = new FocasProbeOptions
+        {
+            Enabled = probeEnabled,
+            Interval = TimeSpan.FromMilliseconds(50),
+            Timeout = TimeSpan.FromMilliseconds(250),
+        },
+        // FixedTree / HandleRecycle / AlarmProjection default off — keep only the data path (+ probe).
+    };
+
+    /// <summary>Rapid data calls against a dead CNC attempt a single connect, then fail fast inside the backoff window.</summary>
+    [Fact]
+    public async Task DeadDevice_ConnectAttemptsFollowBackoffSchedule()
+    {
+        var factory = new FakeFocasClientFactory
+        {
+            Customise = () => new FakeFocasClient
+            {
+                ThrowOnConnect = true,
+                Exception = new InvalidOperationException("cnc down"),
+            },
+        };
+        var drv = new FocasDriver(Options(probeEnabled: false), "focas-1", factory);
+        await drv.InitializeAsync("{}", CancellationToken.None);
+
+        for (var i = 0; i < 6; i++)
+            await drv.ReadAsync(["R"], CancellationToken.None);
+
+        // One real connect attempt; the remaining five fail fast inside the window — no new socket
+        // is created (the fake factory records one client per attempted connect).
+        factory.Clients.Count.ShouldBe(1);
+    }
+
+    /// <summary>The probe bypasses the backoff window and a successful connect resets it so the next data call succeeds immediately.</summary>
+    [Fact]
+    public async Task ProbeBypassesBackoff_AndSuccessResets()
+    {
+        var fail = true;
+        var factory = new FakeFocasClientFactory
+        {
+            Customise = () => new FakeFocasClient
+            {
+                ThrowOnConnect = fail,
+                Exception = new InvalidOperationException("cnc down"),
+            },
+        };
+        var drv = new FocasDriver(Options(probeEnabled: true), "focas-1", factory);
+        await drv.InitializeAsync("{}", CancellationToken.None);
+
+        var down = await drv.ReadAsync(["R"], CancellationToken.None);
+        down[0].StatusCode.ShouldBe(FocasStatusMapper.BadCommunicationError);
+
+        // Device recovers. The probe bypasses the still-open window, reconnects, and resets it so
+        // the following data read succeeds with no residual delay.
+        fail = false;
+        var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(3);
+        DataValueSnapshot? good = null;
+        while (DateTime.UtcNow < deadline)
+        {
+            var r = await drv.ReadAsync(["R"], CancellationToken.None);
+            if (r[0].StatusCode == FocasStatusMapper.Good) { good = r[0]; break; }
+            await Task.Delay(25, CancellationToken.None);
+        }
+
+        good.ShouldNotBeNull("probe-driven reconnect must reset the backoff so data reads recover");
+    }
+}