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268 lines (234 loc) · 10 KB
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using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
namespace Microsoft.AspNetCore.NodeServices.HostingModels
{
/// <summary>
/// Class responsible for launching a Node child process on the local machine, determining when it is ready to
/// accept invocations, detecting if it dies on its own, and finally terminating it on disposal.
///
/// This abstract base class uses the input/output streams of the child process to perform a simple handshake
/// to determine when the child process is ready to accept invocations. This is agnostic to the mechanism that
/// derived classes use to actually perform the invocations (e.g., they could use HTTP-RPC, or a binary TCP
/// protocol, or any other RPC-type mechanism).
/// </summary>
/// <seealso cref="Microsoft.AspNetCore.NodeServices.HostingModels.INodeInstance" />
public abstract class OutOfProcessNodeInstance : INodeInstance
{
private const string ConnectionEstablishedMessage = "[Microsoft.AspNetCore.NodeServices:Listening]";
private readonly TaskCompletionSource<object> _connectionIsReadySource = new TaskCompletionSource<object>();
private bool _disposed;
private readonly StringAsTempFile _entryPointScript;
private FileSystemWatcher _fileSystemWatcher;
private readonly Process _nodeProcess;
private bool _nodeProcessNeedsRestart;
private readonly string[] _watchFileExtensions;
public OutOfProcessNodeInstance(
string entryPointScript,
string projectPath,
string[] watchFileExtensions,
string commandLineArguments)
{
_entryPointScript = new StringAsTempFile(entryPointScript);
var startInfo = PrepareNodeProcessStartInfo(_entryPointScript.FileName, projectPath, commandLineArguments);
_nodeProcess = LaunchNodeProcess(startInfo);
_watchFileExtensions = watchFileExtensions;
_fileSystemWatcher = BeginFileWatcher(projectPath);
ConnectToInputOutputStreams();
}
public async Task<T> InvokeExportAsync<T>(string moduleName, string exportNameOrNull, params object[] args)
{
if (_nodeProcess.HasExited || _nodeProcessNeedsRestart)
{
// This special kind of exception triggers a transparent retry - NodeServicesImpl will launch
// a new Node instance and pass the invocation to that one instead.
var message = _nodeProcess.HasExited
? "The Node process has exited"
: "The Node process needs to restart";
throw new NodeInvocationException(message, null, nodeInstanceUnavailable: true);
}
// Wait until the connection is established. This will throw if the connection fails to initialize.
await _connectionIsReadySource.Task;
return await InvokeExportAsync<T>(new NodeInvocationInfo
{
ModuleName = moduleName,
ExportedFunctionName = exportNameOrNull,
Args = args
});
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected abstract Task<T> InvokeExportAsync<T>(NodeInvocationInfo invocationInfo);
// This method is virtual, as it provides a way to override the NODE_PATH or the path to node.exe
protected virtual ProcessStartInfo PrepareNodeProcessStartInfo(
string entryPointFilename, string projectPath, string commandLineArguments)
{
var startInfo = new ProcessStartInfo("node")
{
Arguments = "\"" + entryPointFilename + "\" " + (commandLineArguments ?? string.Empty),
UseShellExecute = false,
RedirectStandardInput = true,
RedirectStandardOutput = true,
RedirectStandardError = true,
WorkingDirectory = projectPath
};
// Append projectPath to NODE_PATH so it can locate node_modules
var existingNodePath = Environment.GetEnvironmentVariable("NODE_PATH") ?? string.Empty;
if (existingNodePath != string.Empty)
{
existingNodePath += ":";
}
var nodePathValue = existingNodePath + Path.Combine(projectPath, "node_modules");
#if NET451
startInfo.EnvironmentVariables["NODE_PATH"] = nodePathValue;
#else
startInfo.Environment["NODE_PATH"] = nodePathValue;
#endif
return startInfo;
}
protected virtual void OnOutputDataReceived(string outputData)
{
Console.WriteLine("[Node] " + outputData);
}
protected virtual void OnErrorDataReceived(string errorData)
{
Console.WriteLine("[Node] " + errorData);
}
protected virtual void Dispose(bool disposing)
{
if (!_disposed)
{
if (disposing)
{
_entryPointScript.Dispose();
EnsureFileSystemWatcherIsDisposed();
}
// Make sure the Node process is finished
// TODO: Is there a more graceful way to end it? Or does this still let it perform any cleanup?
if (!_nodeProcess.HasExited)
{
_nodeProcess.Kill();
}
_disposed = true;
}
}
private void EnsureFileSystemWatcherIsDisposed()
{
if (_fileSystemWatcher != null)
{
_fileSystemWatcher.Dispose();
_fileSystemWatcher = null;
}
}
private static Process LaunchNodeProcess(ProcessStartInfo startInfo)
{
var process = Process.Start(startInfo);
// On Mac at least, a killed child process is left open as a zombie until the parent
// captures its exit code. We don't need the exit code for this process, and don't want
// to use process.WaitForExit() explicitly (we'd have to block the thread until it really
// has exited), but we don't want to leave zombies lying around either. It's sufficient
// to use process.EnableRaisingEvents so that .NET will grab the exit code and let the
// zombie be cleaned away without having to block our thread.
process.EnableRaisingEvents = true;
return process;
}
private void ConnectToInputOutputStreams()
{
var initializationIsCompleted = false;
_nodeProcess.OutputDataReceived += (sender, evt) =>
{
if (evt.Data == ConnectionEstablishedMessage && !initializationIsCompleted)
{
_connectionIsReadySource.SetResult(null);
initializationIsCompleted = true;
}
else if (evt.Data != null)
{
OnOutputDataReceived(evt.Data);
}
};
_nodeProcess.ErrorDataReceived += (sender, evt) =>
{
if (evt.Data != null)
{
if (!initializationIsCompleted)
{
_connectionIsReadySource.SetException(
new InvalidOperationException("The Node.js process failed to initialize: " + evt.Data));
initializationIsCompleted = true;
}
else
{
OnErrorDataReceived(evt.Data);
}
}
};
_nodeProcess.BeginOutputReadLine();
_nodeProcess.BeginErrorReadLine();
}
private FileSystemWatcher BeginFileWatcher(string rootDir)
{
if (_watchFileExtensions == null || _watchFileExtensions.Length == 0)
{
// Nothing to watch
return null;
}
var watcher = new FileSystemWatcher(rootDir)
{
IncludeSubdirectories = true,
NotifyFilter = NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName
};
watcher.Changed += OnFileChanged;
watcher.Created += OnFileChanged;
watcher.Deleted += OnFileChanged;
watcher.Renamed += OnFileRenamed;
watcher.EnableRaisingEvents = true;
return watcher;
}
private void OnFileChanged(object source, FileSystemEventArgs e)
{
if (IsFilenameBeingWatched(e.FullPath))
{
RestartDueToFileChange(e.FullPath);
}
}
private void OnFileRenamed(object source, RenamedEventArgs e)
{
if (IsFilenameBeingWatched(e.OldFullPath) || IsFilenameBeingWatched(e.FullPath))
{
RestartDueToFileChange(e.OldFullPath);
}
}
private bool IsFilenameBeingWatched(string fullPath)
{
if (string.IsNullOrEmpty(fullPath))
{
return false;
}
else
{
var actualExtension = Path.GetExtension(fullPath) ?? string.Empty;
return _watchFileExtensions.Any(actualExtension.Equals);
}
}
private void RestartDueToFileChange(string fullPath)
{
// TODO: Use proper logger
Console.WriteLine($"Node will restart because file changed: {fullPath}");
_nodeProcessNeedsRestart = true;
// There's no need to watch for any more changes, since we're already restarting, and if the
// restart takes some time (e.g., due to connection draining), we could end up getting duplicate
// notifications.
EnsureFileSystemWatcherIsDisposed();
}
~OutOfProcessNodeInstance()
{
Dispose(false);
}
}
}