Improve gateway reliability and dashboard docs

src/MxGateway.Tests/Gateway/Workers/WorkerClientTests.cs

@@ -2,6 +2,7 @@ using System.IO.Pipes;
 using Google.Protobuf.WellKnownTypes;
 using MxGateway.Contracts;
 using MxGateway.Contracts.Proto;
+using MxGateway.Server.Metrics;
 using MxGateway.Server.Workers;
 
 namespace MxGateway.Tests.Gateway.Workers;
@@ -152,6 +153,27 @@ public sealed class WorkerClientTests
         Assert.Equal(WorkerClientState.Faulted, client.State);
     }
 
+    [Fact]
+    public async Task ReadLoop_WhenPipeDisconnects_StopsRunningWorkerMetric()
+    {
+        await using PipePair pipePair = await PipePair.CreateAsync();
+        using GatewayMetrics metrics = new();
+        await using WorkerClient client = CreateClient(pipePair, metrics: metrics);
+        await CompleteHandshakeAsync(client, pipePair);
+
+        Assert.Equal(1, metrics.GetSnapshot().WorkersRunning);
+
+        await pipePair.DisposeWorkerSideAsync();
+
+        await WaitUntilAsync(
+            () => client.State == WorkerClientState.Faulted,
+            TestTimeout);
+
+        GatewayMetricsSnapshot snapshot = metrics.GetSnapshot();
+        Assert.Equal(0, snapshot.WorkersRunning);
+        Assert.Equal(1, snapshot.WorkerExits);
+    }
+
     [Fact]
     public async Task ReadLoop_WhenHeartbeatArrives_UpdatesLastHeartbeatAndWorkerProcess()
     {
@@ -193,7 +215,8 @@ public sealed class WorkerClientTests
 
     private static WorkerClient CreateClient(
         PipePair pipePair,
-        WorkerClientOptions? options = null)
+        WorkerClientOptions? options = null,
+        GatewayMetrics? metrics = null)
     {
         WorkerFrameProtocolOptions frameOptions = new(SessionId);
         WorkerClientConnection connection = new(
@@ -202,7 +225,7 @@ public sealed class WorkerClientTests
             pipePair.GatewayStream,
             frameOptions);
 
-        return new WorkerClient(connection, options);
+        return new WorkerClient(connection, options, metrics);
     }
 
     private static async Task CompleteHandshakeAsync(