Implement worker heartbeat watchdog

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

@@ -1,4 +1,5 @@
 using System.IO.Pipes;
+using Google.Protobuf.WellKnownTypes;
 using MxGateway.Contracts;
 using MxGateway.Contracts.Proto;
 using MxGateway.Server.Workers;
@@ -151,6 +152,24 @@ public sealed class WorkerClientTests
         Assert.Equal(WorkerClientState.Faulted, client.State);
     }
 
+    [Fact]
+    public async Task ReadLoop_WhenHeartbeatArrives_UpdatesLastHeartbeatAndWorkerProcess()
+    {
+        await using PipePair pipePair = await PipePair.CreateAsync();
+        await using WorkerClient client = CreateClient(pipePair);
+        await CompleteHandshakeAsync(client, pipePair);
+        DateTimeOffset previousHeartbeat = client.LastHeartbeatAt;
+
+        await Task.Delay(TimeSpan.FromMilliseconds(20));
+        await pipePair.WorkerWriter.WriteAsync(CreateHeartbeatEnvelope(workerProcessId: 9876));
+
+        await WaitUntilAsync(
+            () => client.ProcessId == 9876 && client.LastHeartbeatAt > previousHeartbeat,
+            TestTimeout);
+
+        Assert.Equal(WorkerClientState.Ready, client.State);
+    }
+
     [Fact]
     public async Task HeartbeatMonitor_WhenHeartbeatExpires_FaultsClient()
     {
@@ -276,6 +295,21 @@ public sealed class WorkerClientTests
             });
     }
 
+    private static WorkerEnvelope CreateHeartbeatEnvelope(int workerProcessId)
+    {
+        return CreateWorkerEnvelope(
+            correlationId: string.Empty,
+            sequence: 20,
+            envelope => envelope.WorkerHeartbeat = new WorkerHeartbeat
+            {
+                WorkerProcessId = workerProcessId,
+                State = WorkerState.Ready,
+                LastStaActivityTimestamp = Timestamp.FromDateTimeOffset(DateTimeOffset.UtcNow),
+                PendingCommandCount = 0,
+                OutboundEventQueueDepth = 0,
+            });
+    }
+
     private static WorkerEnvelope CreateWorkerEnvelope(
         string correlationId,
         ulong sequence,