When Node is launched with a debug listener, disable connection draining on restart. Fixesaspnet#506.

Author: SteveSandersonMS

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

@@ -13,6 +13,13 @@ public class NodeInvocationException : Exception
 /// </summary>
 publicboolNodeInstanceUnavailable{get;privateset;}
 
+/// <summary>
+/// If true, indicates that even though the invocation failed because the Node.js instance could not be reached
+/// or needs to be restarted, that Node.js instance may remain alive for a period in order to complete any
+/// outstanding requests.
+/// </summary>
+publicboolAllowConnectionDraining{get;privateset;}
+
 /// <summary>
 /// Creates a new instance of <see cref="NodeInvocationException"/>.
 /// </summary>
@@ -29,10 +36,20 @@ public NodeInvocationException(string message, string details)
 /// <param name="message">A description of the exception.</param>
 /// <param name="details">Additional information, such as a Node.js stack trace, representing the exception.</param>
 /// <param name="nodeInstanceUnavailable">Specifies a value for the <see cref="NodeInstanceUnavailable"/> flag.</param>
-publicNodeInvocationException(stringmessage,stringdetails,boolnodeInstanceUnavailable)
+/// <param name="allowConnectionDraining">Specifies a value for the <see cref="AllowConnectionDraining"/> flag.</param>
+publicNodeInvocationException(stringmessage,stringdetails,boolnodeInstanceUnavailable,boolallowConnectionDraining)
 :this(message,details)
 {
+// Reject a meaningless combination of flags
+if(allowConnectionDraining&&!nodeInstanceUnavailable)
+{
+thrownewArgumentException(
+$"The '${nameof(allowConnectionDraining) }' parameter cannot be true "+
+$"unless the '${nameof(nodeInstanceUnavailable) }' parameter is also true.");
+}
+
 NodeInstanceUnavailable=nodeInstanceUnavailable;
+AllowConnectionDraining=allowConnectionDraining;
 }
 }
 }

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

@@ -42,6 +42,7 @@ npm install -g node-inspector
 privatereadonlyStringAsTempFile_entryPointScript;
 privateFileSystemWatcher_fileSystemWatcher;
 privateint_invocationTimeoutMilliseconds;
+privatebool_launchWithDebugging;
 privatereadonlyProcess_nodeProcess;
 privateint?_nodeDebuggingPort;
 privatebool_nodeProcessNeedsRestart;
@@ -78,9 +79,10 @@ public OutOfProcessNodeInstance(
 OutputLogger=nodeOutputLogger;
 _entryPointScript=newStringAsTempFile(entryPointScript);
 _invocationTimeoutMilliseconds=invocationTimeoutMilliseconds;
+_launchWithDebugging=launchWithDebugging;
 
 varstartInfo=PrepareNodeProcessStartInfo(_entryPointScript.FileName,projectPath,commandLineArguments,
-environmentVars,launchWithDebugging,debuggingPort);
+environmentVars,_launchWithDebugging,debuggingPort);
 _nodeProcess=LaunchNodeProcess(startInfo);
 _watchFileExtensions=watchFileExtensions;
 _fileSystemWatcher=BeginFileWatcher(projectPath);
@@ -103,10 +105,17 @@ public async Task<T> InvokeExportAsync<T>(
 {
 // This special kind of exception triggers a transparent retry - NodeServicesImpl will launch
 // a new Node instance and pass the invocation to that one instead.
+// Note that if the Node process is listening for debugger connections, then we need it to shut
+// down immediately and not stay open for connection draining (because if it did, the new Node
+// instance wouldn't able to start, because the old one would still hold the debugging port).
 varmessage=_nodeProcess.HasExited
 ?"The Node process has exited"
 :"The Node process needs to restart";
-thrownewNodeInvocationException(message,null,nodeInstanceUnavailable:true);
+thrownewNodeInvocationException(
+message,
+details:null,
+nodeInstanceUnavailable:true,
+allowConnectionDraining:!_launchWithDebugging);
 }
 
 // Construct a new cancellation token that combines the supplied token with the configured invocation

src/Microsoft.AspNetCore.NodeServices/NodeServicesImpl.cs

@@ -72,7 +72,8 @@ private async Task<T> InvokeExportWithPossibleRetryAsync<T>(string moduleName, s
 {
 if(_currentNodeInstance==nodeInstance)
 {
-DisposeNodeInstance(_currentNodeInstance,delay:ConnectionDrainingTimespan);
+vardisposalDelay=ex.AllowConnectionDraining?ConnectionDrainingTimespan:TimeSpan.Zero;
+DisposeNodeInstance(_currentNodeInstance,disposalDelay);
 _currentNodeInstance=null;
 }
 }