Support cancellation of NodeServices invocations

src/Microsoft.AspNetCore.NodeServices/HostingModels/HttpNodeInstance.cs

@@ -4,6 +4,7 @@ using System.IO;
 using System.Net.Http;
 using System.Text;
 using System.Text.RegularExpressions;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using Newtonsoft.Json;
@@ -57,15 +58,17 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
             return $"--port {port}";
         }
 
-        protected override async Task<T> InvokeExportAsync<T>(NodeInvocationInfo invocationInfo)
+        protected override async Task<T> InvokeExportAsync<T>(
+            NodeInvocationInfo invocationInfo, CancellationToken cancellationToken)
         {
             var payloadJson = JsonConvert.SerializeObject(invocationInfo, jsonSerializerSettings);
             var payload = new StringContent(payloadJson, Encoding.UTF8, "application/json");
-            var response = await _client.PostAsync("http://localhost:" + _portNumber, payload);
+            var response = await _client.PostAsync("http://localhost:" + _portNumber, payload, cancellationToken);
 
             if (!response.IsSuccessStatusCode)
             {
-                var responseErrorString = await response.Content.ReadAsStringAsync();
+                // Unfortunately there's no true way to cancel ReadAsStringAsync calls, hence AbandonIfCancelled
+                var responseErrorString = await response.Content.ReadAsStringAsync().OrThrowOnCancellation(cancellationToken);
                 throw new Exception("Call to Node module failed with error: " + responseErrorString);
             }
 
@@ -81,11 +84,11 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
                             typeof(T).FullName);
                     }
 
-                    var responseString = await response.Content.ReadAsStringAsync();
+                    var responseString = await response.Content.ReadAsStringAsync().OrThrowOnCancellation(cancellationToken);
                     return (T)(object)responseString;
 
                 case "application/json":
-                    var responseJson = await response.Content.ReadAsStringAsync();
+                    var responseJson = await response.Content.ReadAsStringAsync().OrThrowOnCancellation(cancellationToken);
                     return JsonConvert.DeserializeObject<T>(responseJson, jsonSerializerSettings);
 
                 case "application/octet-stream":
@@ -97,7 +100,7 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
                             typeof(T).FullName + ". Instead you must use the generic type System.IO.Stream.");
                     }
 
-                    return (T)(object)(await response.Content.ReadAsStreamAsync());
+                    return (T)(object)(await response.Content.ReadAsStreamAsync().OrThrowOnCancellation(cancellationToken));
 
                 default:
                     throw new InvalidOperationException("Unexpected response content type: " + responseContentType.MediaType);

src/Microsoft.AspNetCore.NodeServices/HostingModels/INodeInstance.cs

@@ -1,10 +1,11 @@
 using System;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Microsoft.AspNetCore.NodeServices.HostingModels
 {
     public interface INodeInstance : IDisposable
     {
-        Task<T> InvokeExportAsync<T>(string moduleName, string exportNameOrNull, params object[] args);
+        Task<T> InvokeExportAsync<T>(CancellationToken cancellationToken, string moduleName, string exportNameOrNull, params object[] args);
     }
 }

src/Microsoft.AspNetCore.NodeServices/HostingModels/OutOfProcessNodeInstance.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 
@@ -67,7 +68,8 @@ If you haven't yet installed node-inspector, you can do so as follows:
             ConnectToInputOutputStreams();
         }
 
-        public async Task<T> InvokeExportAsync<T>(string moduleName, string exportNameOrNull, params object[] args)
+        public async Task<T> InvokeExportAsync<T>(
+            CancellationToken cancellationToken, string moduleName, string exportNameOrNull, params object[] args)
         {
             if (_nodeProcess.HasExited || _nodeProcessNeedsRestart)
             {
@@ -79,15 +81,17 @@ If you haven't yet installed node-inspector, you can do so as follows:
                 throw new NodeInvocationException(message, null, nodeInstanceUnavailable: true);
             }
 
-            // Wait until the connection is established. This will throw if the connection fails to initialize.
+            // Wait until the connection is established. This will throw if the connection fails to initialize,
-            await _connectionIsReadySource.Task;
+            // or if cancellation is requested first. Note that we can't really cancel the "establishing connection"
+            // task because that's shared with all callers, but we can stop waiting for it if this call is cancelled.
+            await _connectionIsReadySource.Task.OrThrowOnCancellation(cancellationToken);
 
             return await InvokeExportAsync<T>(new NodeInvocationInfo
             {
                 ModuleName = moduleName,
                 ExportedFunctionName = exportNameOrNull,
                 Args = args
-            });
+            }, cancellationToken);
         }
 
         public void Dispose()
@@ -96,7 +100,9 @@ If you haven't yet installed node-inspector, you can do so as follows:
             GC.SuppressFinalize(this);
         }
 
-        protected abstract Task<T> InvokeExportAsync<T>(NodeInvocationInfo invocationInfo);
+        protected abstract Task<T> InvokeExportAsync<T>(
+            NodeInvocationInfo invocationInfo,
+            CancellationToken cancellationToken);
 
         // This method is virtual, as it provides a way to override the NODE_PATH or the path to node.exe
         protected virtual ProcessStartInfo PrepareNodeProcessStartInfo(

src/Microsoft.AspNetCore.NodeServices/HostingModels/SocketNodeInstance.cs

@@ -57,7 +57,7 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
             _socketAddress = socketAddress;
         }
 
-        protected override async Task<T> InvokeExportAsync<T>(NodeInvocationInfo invocationInfo)
+        protected override async Task<T> InvokeExportAsync<T>(NodeInvocationInfo invocationInfo, CancellationToken cancellationToken)
         {
             if (_connectionHasFailed)
             {
@@ -70,7 +70,12 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
 
             if (_virtualConnectionClient == null)
             {
-                await EnsureVirtualConnectionClientCreated();
+                // Although we could pass the cancellationToken into EnsureVirtualConnectionClientCreated and
+                // have it signal cancellations upstream, that would be a bad thing to do, because all callers
+                // wait for the same connection task. There's no reason why the first caller should have the
+                // special ability to cancel the connection process in a way that would affect subsequent
+                // callers. So, each caller just independently stops awaiting connection if that call is cancelled.
+                await EnsureVirtualConnectionClientCreated().OrThrowOnCancellation(cancellationToken);
             }
 
             // For each invocation, we open a new virtual connection. This gives an API equivalent to opening a new
@@ -83,7 +88,7 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
                 virtualConnection = _virtualConnectionClient.OpenVirtualConnection();
 
                 // Send request
-                await WriteJsonLineAsync(virtualConnection, invocationInfo);
+                await WriteJsonLineAsync(virtualConnection, invocationInfo, cancellationToken);
 
                 // Determine what kind of response format is expected
                 if (typeof(T) == typeof(Stream))
@@ -96,7 +101,7 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
                 else
                 {
                     // Parse and return non-streamed JSON response
-                    var response = await ReadJsonAsync<RpcJsonResponse<T>>(virtualConnection);
+                    var response = await ReadJsonAsync<RpcJsonResponse<T>>(virtualConnection, cancellationToken);
                     if (response.ErrorMessage != null)
                     {
                         throw new NodeInvocationException(response.ErrorMessage, response.ErrorDetails);
@@ -163,27 +168,27 @@ namespace Microsoft.AspNetCore.NodeServices.HostingModels
             base.Dispose(disposing);
         }
 
-        private static async Task WriteJsonLineAsync(Stream stream, object serializableObject)
+        private static async Task WriteJsonLineAsync(Stream stream, object serializableObject, CancellationToken cancellationToken)
         {
             var json = JsonConvert.SerializeObject(serializableObject, jsonSerializerSettings);
             var bytes = Encoding.UTF8.GetBytes(json + '\n');
-            await stream.WriteAsync(bytes, 0, bytes.Length);
+            await stream.WriteAsync(bytes, 0, bytes.Length, cancellationToken);
         }
 
-        private static async Task<T> ReadJsonAsync<T>(Stream stream)
+        private static async Task<T> ReadJsonAsync<T>(Stream stream, CancellationToken cancellationToken)
         {
-            var json = Encoding.UTF8.GetString(await ReadAllBytesAsync(stream));
+            var json = Encoding.UTF8.GetString(await ReadAllBytesAsync(stream, cancellationToken));
             return JsonConvert.DeserializeObject<T>(json, jsonSerializerSettings);
         }
 
-        private static async Task<byte[]> ReadAllBytesAsync(Stream input)
+        private static async Task<byte[]> ReadAllBytesAsync(Stream input, CancellationToken cancellationToken)
         {
             byte[] buffer = new byte[16 * 1024];
 
             using (var ms = new MemoryStream())
             {
                 int read;
-                while ((read = await input.ReadAsync(buffer, 0, buffer.Length)) > 0)
+                while ((read = await input.ReadAsync(buffer, 0, buffer.Length, cancellationToken)) > 0)
                 {
                     ms.Write(buffer, 0, read);
                 }

src/Microsoft.AspNetCore.NodeServices/INodeServices.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Microsoft.AspNetCore.NodeServices
@@ -6,8 +7,11 @@ namespace Microsoft.AspNetCore.NodeServices
     public interface INodeServices : IDisposable
     {
         Task<T> InvokeAsync<T>(string moduleName, params object[] args);
+        Task<T> InvokeAsync<T>(CancellationToken cancellationToken, string moduleName, params object[] args);
 
         Task<T> InvokeExportAsync<T>(string moduleName, string exportedFunctionName, params object[] args);
+        Task<T> InvokeExportAsync<T>(CancellationToken cancellationToken, string moduleName, string exportedFunctionName, params object[] args);
+
 
         [Obsolete("Use InvokeAsync instead")]
         Task<T> Invoke<T>(string moduleName, params object[] args);

src/Microsoft.AspNetCore.NodeServices/NodeServicesImpl.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.NodeServices.HostingModels;
 
@@ -34,19 +35,29 @@ namespace Microsoft.AspNetCore.NodeServices
             return InvokeExportAsync<T>(moduleName, null, args);
         }
 
-        public Task<T> InvokeExportAsync<T>(string moduleName, string exportedFunctionName, params object[] args)
+        public Task<T> InvokeAsync<T>(CancellationToken cancellationToken, string moduleName, params object[] args)
         {
-            return InvokeExportWithPossibleRetryAsync<T>(moduleName, exportedFunctionName, args, allowRetry: true);
+            return InvokeExportAsync<T>(cancellationToken, moduleName, null, args);
         }
 
-        public async Task<T> InvokeExportWithPossibleRetryAsync<T>(string moduleName, string exportedFunctionName, object[] args, bool allowRetry)
+        public Task<T> InvokeExportAsync<T>(string moduleName, string exportedFunctionName, params object[] args)
+        {
+            return InvokeExportWithPossibleRetryAsync<T>(moduleName, exportedFunctionName, args, /* allowRetry */ true, CancellationToken.None);
+        }
+
+        public Task<T> InvokeExportAsync<T>(CancellationToken cancellationToken, string moduleName, string exportedFunctionName, params object[] args)
+        {
+            return InvokeExportWithPossibleRetryAsync<T>(moduleName, exportedFunctionName, args, /* allowRetry */ true, cancellationToken);
+        }
+
+        public async Task<T> InvokeExportWithPossibleRetryAsync<T>(string moduleName, string exportedFunctionName, object[] args, bool allowRetry, CancellationToken cancellationToken)
         {
             ThrowAnyOutstandingDelayedDisposalException();
             var nodeInstance = GetOrCreateCurrentNodeInstance();
 
             try
             {
-                return await nodeInstance.InvokeExportAsync<T>(moduleName, exportedFunctionName, args);
+                return await nodeInstance.InvokeExportAsync<T>(cancellationToken, moduleName, exportedFunctionName, args);
             }
             catch (NodeInvocationException ex)
             {
@@ -69,7 +80,7 @@ namespace Microsoft.AspNetCore.NodeServices
                     // One the next call, don't allow retries, because we could get into an infinite retry loop, or a long retry
                     // loop that masks an underlying problem. A newly-created Node instance should be able to accept invocations,
                     // or something more serious must be wrong.
-                    return await InvokeExportWithPossibleRetryAsync<T>(moduleName, exportedFunctionName, args, allowRetry: false);
+                    return await InvokeExportWithPossibleRetryAsync<T>(moduleName, exportedFunctionName, args, /* allowRetry */ false, cancellationToken);
                 }
                 else
                 {

src/Microsoft.AspNetCore.NodeServices/Util/TaskExtensions.cs

@@ -0,0 +1,30 @@
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.AspNetCore.NodeServices
+{
+    internal static class TaskExtensions
+    {
+        public static Task OrThrowOnCancellation(this Task task, CancellationToken cancellationToken)
+        {
+            return task.IsCompleted
+                ? task // If the task is already completed, no need to wrap it in a further layer of task
+                : task.ContinueWith(
+                    _ => {}, // If the task completes, allow execution to continue
+                    cancellationToken,
+                    TaskContinuationOptions.ExecuteSynchronously,
+                    TaskScheduler.Default);
+        }
+
+        public static Task<T> OrThrowOnCancellation<T>(this Task<T> task, CancellationToken cancellationToken)
+        {
+            return task.IsCompleted
+                ? task // If the task is already completed, no need to wrap it in a further layer of task
+                : task.ContinueWith(
+                    t => t.Result, // If the task completes, pass through its result
+                    cancellationToken,
+                    TaskContinuationOptions.ExecuteSynchronously,
+                    TaskScheduler.Default);
+        }
+    }
+}