DockerRunner: include stderr in log on failure. (#1059)

src/Microsoft.Tye.Core/ProcessUtil.cs

@@ -114,9 +114,12 @@ namespace Microsoft.Tye
 
             process.Exited += (_, e) =>
             {
-                // Even though the Exited event has been raised, WaitForExit() must still be called to ensure the output buffers
-                // have been flushed before the process is considered completely done.
-                process.WaitForExit();
+                lock (process)
+                {
+                    // Even though the Exited event has been raised, WaitForExit() must still be called to ensure the output buffers
+                    // have been flushed before the process is considered completely done.
+                    process.WaitForExit();
+                }
 
                 if (throwOnError && process.ExitCode != 0)
                 {
@@ -128,11 +131,15 @@ namespace Microsoft.Tye
                 }
             };
 
-            process.Start();
-            onStart?.Invoke(process.Id);
+            // lock ensures we're reading output when WaitForExit is called in process.Exited event.
+            lock (process)
+            {
+                process.Start();
+                onStart?.Invoke(process.Id);
 
-            process.BeginOutputReadLine();
-            process.BeginErrorReadLine();
+                process.BeginOutputReadLine();
+                process.BeginErrorReadLine();
+            }
 
             var cancelledTcs = new TaskCompletionSource<object?>();
             await using var _ = cancellationToken.Register(() => cancelledTcs.TrySetResult(null));

src/Microsoft.Tye.Hosting/DockerRunner.cs

@@ -311,16 +311,17 @@ namespace Microsoft.Tye.Hosting
                 status.DockerNetwork = dockerNetwork;
 
                 WriteReplicaToStore(replica);
+                var stderr = new StringBuilder();
                 var result = await application.ContainerEngine.RunAsync(
                     command,
                     throwOnError: false,
                     cancellationToken: cancellationToken,
                     outputDataReceived: data => service.Logs.OnNext($"[{replica}]: {data}"),
-                    errorDataReceived: data => service.Logs.OnNext($"[{replica}]: {data}"));
+                    errorDataReceived: data => { service.Logs.OnNext($"[{replica}]: {data}"); stderr.AppendLine(data); });
 
                 if (result.ExitCode != 0)
                 {
-                    _logger.LogError("docker run failed for {ServiceName} with exit code {ExitCode}:" + result.StandardError, service.Description.Name, result.ExitCode);
+                    _logger.LogError("docker run failed for {ServiceName} with exit code {ExitCode}: " + stderr, service.Description.Name, result.ExitCode);
                     service.Replicas.TryRemove(replica, out var _);
                     service.ReplicaEvents.OnNext(new ReplicaEvent(ReplicaState.Removed, status));