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fix(lmxproxy): await COM subscription creation to fix Subscribe flakiness

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SubscriptionManager.Subscribe was fire-and-forgetting the MxAccess COM
subscription creation. The initial OnDataChange callback could fire
before the subscription was established, losing the first (and possibly
only) value update. Changed to async SubscribeAsync that awaits
CreateMxAccessSubscriptionsAsync before returning the channel reader.

Subscribe_ReceivesUpdates now passes 5/5 consecutive runs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
2026-03-22 23:48:01 -04:00
parent 84b7b6a7a9
commit b218773ab0
4 changed files with 31 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Grpc/Services/ScadaGrpcService.cs
View File

@@ -360,7 +360,7 @@ namespace ZB.MOM.WW.LmxProxy.Host.Grpc.Services
throw new RpcException(new GrpcStatus(StatusCode.Unauthenticated, "Invalid session"));
}
var reader = _subscriptionManager.Subscribe(
var reader = await _subscriptionManager.SubscribeAsync(
request.SessionId, request.Tags, context.CancellationToken);
try

11
lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Subscriptions/SubscriptionManager.cs
View File

@@ -42,8 +42,10 @@ namespace ZB.MOM.WW.LmxProxy.Host.Subscriptions
/// <summary>
/// Creates a subscription for a client. Returns a ChannelReader to stream from.
/// Awaits COM subscription creation so the initial OnDataChange callback
/// is not missed.
/// </summary>
public ChannelReader<(string address, Vtq vtq)> Subscribe(
public async Task<ChannelReader<(string address, Vtq vtq)>> SubscribeAsync(
string clientId, IEnumerable<string> addresses, CancellationToken ct)
{
var channel = Channel.CreateBounded<(string address, Vtq vtq)>(
@@ -83,10 +85,13 @@ namespace ZB.MOM.WW.LmxProxy.Host.Subscriptions
_rwLock.ExitWriteLock();
}
// Create MxAccess COM subscriptions for newly subscribed tags
// Create MxAccess COM subscriptions — awaited so the initial
// OnDataChange (first value delivery after AdviseSupervisory)
// is not lost. The channel and routing are already set up above,
// so any callback that fires during this call will be delivered.
if (newTags.Count > 0)
{
_ = CreateMxAccessSubscriptionsAsync(newTags);
await CreateMxAccessSubscriptionsAsync(newTags);
}
// Register cancellation cleanup

2
lmxproxy/tests/ZB.MOM.WW.LmxProxy.Host.Tests/Health/HealthCheckServiceTests.cs
View File

@@ -104,7 +104,7 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Health
for (int i = 0; i < 101; i++)
{
using var cts = new CancellationTokenSource();
sm.Subscribe("client-" + i, new[] { "tag1" }, cts.Token);
await sm.SubscribeAsync("client-" + i, new[] { "tag1" }, cts.Token);
}
var svc = new HealthCheckService(client, sm, pm);

42
lmxproxy/tests/ZB.MOM.WW.LmxProxy.Host.Tests/Subscriptions/SubscriptionManagerTests.cs
View File

@@ -47,11 +47,11 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
}
[Fact]
public void Subscribe_ReturnsChannelReader()
public async Task Subscribe_ReturnsChannelReader()
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
var reader = sm.Subscribe("client1", new[] { "Tag1", "Tag2" }, cts.Token);
var reader = await sm.SubscribeAsync("client1", new[] { "Tag1", "Tag2" }, cts.Token);
reader.Should().NotBeNull();
}
@@ -60,7 +60,7 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
var reader = sm.Subscribe("client1", new[] { "Motor.Speed" }, cts.Token);
var reader = await sm.SubscribeAsync("client1", new[] { "Motor.Speed" }, cts.Token);
var vtq = Vtq.Good(42.0);
sm.OnTagValueChanged("Motor.Speed", vtq);
@@ -76,8 +76,8 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
var reader1 = sm.Subscribe("client1", new[] { "Motor.Speed" }, cts.Token);
var reader2 = sm.Subscribe("client2", new[] { "Motor.Speed" }, cts.Token);
var reader1 = await sm.SubscribeAsync("client1", new[] { "Motor.Speed" }, cts.Token);
var reader2 = await sm.SubscribeAsync("client2", new[] { "Motor.Speed" }, cts.Token);
sm.OnTagValueChanged("Motor.Speed", Vtq.Good(99.0));
@@ -88,11 +88,11 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
}
[Fact]
public void OnTagValueChanged_NonSubscribedTag_NoDelivery()
public async Task OnTagValueChanged_NonSubscribedTag_NoDelivery()
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
var reader = sm.Subscribe("client1", new[] { "Motor.Speed" }, cts.Token);
var reader = await sm.SubscribeAsync("client1", new[] { "Motor.Speed" }, cts.Token);
sm.OnTagValueChanged("Motor.Torque", Vtq.Good(10.0));
@@ -101,11 +101,11 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
}
[Fact]
public void UnsubscribeClient_CompletesChannel()
public async Task UnsubscribeClient_CompletesChannel()
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
var reader = sm.Subscribe("client1", new[] { "Motor.Speed" }, cts.Token);
var reader = await sm.SubscribeAsync("client1", new[] { "Motor.Speed" }, cts.Token);
sm.UnsubscribeClient("client1");
@@ -114,11 +114,11 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
}
[Fact]
public void UnsubscribeClient_RemovesFromTagSubscriptions()
public async Task UnsubscribeClient_RemovesFromTagSubscriptions()
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
sm.Subscribe("client1", new[] { "Motor.Speed" }, cts.Token);
await sm.SubscribeAsync("client1", new[] { "Motor.Speed" }, cts.Token);
sm.UnsubscribeClient("client1");
@@ -128,12 +128,12 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
}
[Fact]
public void RefCounting_LastClientUnsubscribeRemovesTag()
public async Task RefCounting_LastClientUnsubscribeRemovesTag()
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
sm.Subscribe("client1", new[] { "Motor.Speed" }, cts.Token);
sm.Subscribe("client2", new[] { "Motor.Speed" }, cts.Token);
await sm.SubscribeAsync("client1", new[] { "Motor.Speed" }, cts.Token);
await sm.SubscribeAsync("client2", new[] { "Motor.Speed" }, cts.Token);
sm.GetStats().TotalTags.Should().Be(1);
@@ -145,11 +145,11 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
}
[Fact]
public void NotifyDisconnection_SendsBadQualityToAll()
public async Task NotifyDisconnection_SendsBadQualityToAll()
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
var reader = sm.Subscribe("client1", new[] { "Motor.Speed", "Motor.Torque" }, cts.Token);
var reader = await sm.SubscribeAsync("client1", new[] { "Motor.Speed", "Motor.Torque" }, cts.Token);
sm.NotifyDisconnection();
@@ -161,11 +161,11 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
}
[Fact]
public void Backpressure_DropOldest_DropsWhenFull()
public async Task Backpressure_DropOldest_DropsWhenFull()
{
using var sm = new SubscriptionManager(new FakeScadaClient(), channelCapacity: 3);
using var cts = new CancellationTokenSource();
var reader = sm.Subscribe("client1", new[] { "Motor.Speed" }, cts.Token);
var reader = await sm.SubscribeAsync("client1", new[] { "Motor.Speed" }, cts.Token);
// Fill the channel beyond capacity
for (int i = 0; i < 10; i++)
@@ -180,12 +180,12 @@ namespace ZB.MOM.WW.LmxProxy.Host.Tests.Subscriptions
}
[Fact]
public void GetStats_ReturnsCorrectCounts()
public async Task GetStats_ReturnsCorrectCounts()
{
using var sm = new SubscriptionManager(new FakeScadaClient());
using var cts = new CancellationTokenSource();
sm.Subscribe("c1", new[] { "Tag1", "Tag2" }, cts.Token);
sm.Subscribe("c2", new[] { "Tag2", "Tag3" }, cts.Token);
await sm.SubscribeAsync("c1", new[] { "Tag1", "Tag2" }, cts.Token);
await sm.SubscribeAsync("c2", new[] { "Tag2", "Tag3" }, cts.Token);
var stats = sm.GetStats();
stats.TotalClients.Should().Be(2);