Joseph Doherty
91 lines
3.8 KiB
C#
91 lines
3.8 KiB
C#
using Shouldly;
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using Xunit;
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using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
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using ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;
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namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests;
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/// <summary>
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/// 05/STAB-8 — a dead TwinCAT device must not be hammered with a full connect attempt on every
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/// data call. The per-device <see cref="ConnectionBackoff"/> gates the connect/create path;
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/// the probe loop bypasses it (its own interval is the recovery cadence) and a successful
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/// connect resets the window instantly so recovery is never delayed. No TC3 fixture exists —
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/// the fake-client suite is authoritative.
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/// </summary>
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[Trait("Category", "Unit")]
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public sealed class TwinCATConnectBackoffTests
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{
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private const string Host = "ads://5.23.91.23.1.1:851";
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private static TwinCATDriverOptions Options(bool probeEnabled) => new()
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{
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Devices = [new TwinCATDeviceOptions(Host)],
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Tags = [new TwinCATTagDefinition("T", Host, "MAIN.T", TwinCATDataType.DInt)],
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Probe = new TwinCATProbeOptions
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{
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Enabled = probeEnabled,
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Interval = TimeSpan.FromMilliseconds(50),
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Timeout = TimeSpan.FromMilliseconds(250),
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},
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EnableControllerBrowse = false,
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};
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/// <summary>Rapid data calls against a dead device attempt a single connect, then fail fast inside the backoff window.</summary>
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[Fact]
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public async Task DeadDevice_ConnectAttemptsFollowBackoffSchedule()
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{
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var factory = new FakeTwinCATClientFactory
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{
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Customise = () => new FakeTwinCATClient
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{
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ThrowOnConnect = true,
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Exception = new InvalidOperationException("device down"),
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},
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};
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var drv = new TwinCATDriver(Options(probeEnabled: false), "twincat-1", factory);
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await drv.InitializeAsync("{}", CancellationToken.None);
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for (var i = 0; i < 6; i++)
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await drv.ReadAsync(["T"], CancellationToken.None);
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// One real connect attempt; the remaining five fail fast inside the 1 s window — no new
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// client is created (the fake factory records one client per attempted connect).
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factory.Clients.Count.ShouldBe(1);
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}
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/// <summary>The probe bypasses the backoff window and a successful connect resets it so the next data call succeeds immediately.</summary>
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[Fact]
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public async Task ProbeBypassesBackoff_AndSuccessResets()
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{
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var fail = true;
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var factory = new FakeTwinCATClientFactory
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{
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Customise = () => new FakeTwinCATClient
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{
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ThrowOnConnect = fail,
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Exception = new InvalidOperationException("device down"),
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},
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};
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var drv = new TwinCATDriver(Options(probeEnabled: true), "twincat-1", factory);
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await drv.InitializeAsync("{}", CancellationToken.None);
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// First data call opens the backoff window on a dead device.
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var down = await drv.ReadAsync(["T"], CancellationToken.None);
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down[0].StatusCode.ShouldBe(TwinCATStatusMapper.BadCommunicationError);
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// Device recovers. The data path is still inside the window, but the probe bypasses it and
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// reconnects — resetting the window so the following data read succeeds with no residual delay.
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fail = false;
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var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(3);
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DataValueSnapshot? good = null;
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while (DateTime.UtcNow < deadline)
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{
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var r = await drv.ReadAsync(["T"], CancellationToken.None);
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if (r[0].StatusCode == TwinCATStatusMapper.Good) { good = r[0]; break; }
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await Task.Delay(25, CancellationToken.None);
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}
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good.ShouldNotBeNull("probe-driven reconnect must reset the backoff so data reads recover");
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}
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}
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