Reading output through async events.

Author: diemol

dotnet/src/webdriver/DriverProcessStartedEventArgs.cs

@@ -19,7 +19,6 @@
 
 using System;
 using System.Diagnostics;
-using System.IO;
 
 namespace OpenQA.Selenium;
 
@@ -41,31 +40,10 @@ public DriverProcessStartedEventArgs(Process driverProcess)
         }
 
         this.ProcessId = driverProcess.Id;
-        if (driverProcess.StartInfo.RedirectStandardOutput && !driverProcess.StartInfo.UseShellExecute)
-        {
-            this.StandardOutputStreamReader = driverProcess.StandardOutput;
-        }
-
-        if (driverProcess.StartInfo.RedirectStandardError && !driverProcess.StartInfo.UseShellExecute)
-        {
-            this.StandardErrorStreamReader = driverProcess.StandardError;
-        }
     }
 
     /// <summary>
     /// Gets the unique ID of the driver executable process.
     /// </summary>
     public int ProcessId { get; }
-
-    /// <summary>
-    /// Gets a <see cref="StreamReader"/> object that can be used to read the contents
-    /// printed to <c>stdout</c> by a driver service process.
-    /// </summary>
-    public StreamReader? StandardOutputStreamReader { get; }
-
-    /// <summary>
-    /// Gets a <see cref="StreamReader"/> object that can be used to read the contents
-    /// printed to <c>stderr</c> by a driver service process.
-    /// </summary>
-    public StreamReader? StandardErrorStreamReader { get; }
 }

dotnet/src/webdriver/DriverService.cs

@@ -25,7 +25,6 @@
 using System.IO;
 using System.Net;
 using System.Net.Http;
-using System.Threading;
 using System.Threading.Tasks;
 using OpenQA.Selenium.Internal.Logging;
 
@@ -253,8 +252,11 @@ public void Start()
         this.driverServiceProcess.StartInfo.UseShellExecute = false;
         this.driverServiceProcess.StartInfo.CreateNoWindow = this.HideCommandPromptWindow;
 
-        this.driverServiceProcess.StartInfo.RedirectStandardOutput = this.WriteDriverLogToConsole;
-        this.driverServiceProcess.StartInfo.RedirectStandardError = this.WriteDriverLogToConsole;
+        this.driverServiceProcess.StartInfo.RedirectStandardOutput = true;
+        this.driverServiceProcess.StartInfo.RedirectStandardError = true;
+
+        this.driverServiceProcess.OutputDataReceived += (s, e) => this.OnDriverProcessDataReceived(s, e, isError: false);
+        this.driverServiceProcess.ErrorDataReceived += (s, e) => this.OnDriverProcessDataReceived(s, e, isError: true);
 
         DriverProcessStartingEventArgs eventArgs = new DriverProcessStartingEventArgs(this.driverServiceProcess.StartInfo);
         this.OnDriverProcessStarting(eventArgs);
@@ -264,6 +266,9 @@ public void Start()
         DriverProcessStartedEventArgs processStartedEventArgs = new DriverProcessStartedEventArgs(this.driverServiceProcess);
         this.OnDriverProcessStarted(processStartedEventArgs);
 
+        this.driverServiceProcess.BeginOutputReadLine();
+        this.driverServiceProcess.BeginErrorReadLine();
+
         if (!serviceAvailable)
         {
             throw new WebDriverException($"Cannot start the driver service on {this.ServiceUrl}");
@@ -318,27 +323,28 @@ protected virtual void OnDriverProcessStarted(DriverProcessStartedEventArgs even
             throw new ArgumentNullException(nameof(eventArgs), "eventArgs must not be null");
         }
 
-        if (this.WriteDriverLogToConsole && eventArgs.StandardOutputStreamReader != null)
+        this.DriverProcessStarted?.Invoke(this, eventArgs);
+    }
+
+    /// <summary>
+    /// Handles the output and error data received from the driver process.
+    /// </summary>
+    /// <param name="sender">The sender of the event.</param>
+    /// <param name="args">The data received event arguments.</param>
+    /// <param name="isError">A value indicating whether the data received is from the error stream.</param>
+    protected virtual void OnDriverProcessDataReceived(object sender, DataReceivedEventArgs args, bool isError)
+    {
+        if (string.IsNullOrEmpty(args.Data))
+            return;
+
+        if (this.WriteDriverLogToConsole && !isError && _logger.IsEnabled(LogEventLevel.Info))
         {
-            var stdoutThread = new Thread(() => ReadStreamSync(eventArgs.StandardOutputStreamReader, "stdout"))
-            {
-                IsBackground = true,
-                Name = "DriverService-stdout"
-            };
-            stdoutThread.Start();
+            _logger.Info(args.Data);
         }
-
-        if (this.WriteDriverLogToConsole && eventArgs.StandardErrorStreamReader != null)
+        if (this.WriteDriverLogToConsole && isError && _logger.IsEnabled(LogEventLevel.Error))
         {
-            var stderrThread = new Thread(() => ReadStreamSync(eventArgs.StandardErrorStreamReader, "stderr"))
-            {
-                IsBackground = true,
-                Name = "DriverService-stderr"
-            };
-            stderrThread.Start();
+            _logger.Error(args.Data);
         }
-
-        this.DriverProcessStarted?.Invoke(this, eventArgs);
     }
 
     /// <summary>
@@ -419,69 +425,4 @@ private bool WaitForServiceInitialization()
 
         return isInitialized;
     }
-
-    private void ReadStreamSync(StreamReader reader, string streamType)
-    {
-        try
-        {
-            string? line;
-            while ((line = reader.ReadLine()) != null)
-            {
-                if (streamType.Equals("stdout", StringComparison.OrdinalIgnoreCase))
-                {
-                    if (_logger.IsEnabled(LogEventLevel.Info))
-                    {
-                        _logger.Info(line);
-                    }
-                }
-                else
-                {
-                    if (_logger.IsEnabled(LogEventLevel.Error))
-                    {
-                        _logger.Error(line);
-                    }
-                }
-            }
-        }
-        catch (Exception ex)
-        {
-            if (_logger.IsEnabled(LogEventLevel.Error))
-            {
-                _logger.Error($"Error reading stream: {ex}");
-            }
-        }
-    }
-
-    private async Task ReadStreamAsync(StreamReader reader, string streamType)
-    {
-        try
-        {
-            string? line;
-            while ((line = await reader.ReadLineAsync()) != null)
-            {
-                if (streamType.Equals("stdout", StringComparison.OrdinalIgnoreCase))
-                {
-                    if (_logger.IsEnabled(LogEventLevel.Info))
-                    {
-                        _logger.Info(line);
-                    }
-                }
-                else
-                {
-                    if (_logger.IsEnabled(LogEventLevel.Error))
-                    {
-                        _logger.Error(line);
-                    }
-                }
-            }
-        }
-        catch (Exception ex)
-        {
-            if (_logger.IsEnabled(LogEventLevel.Error))
-            {
-                _logger.Error($"Error reading stream: {ex}");
-            }
-        }
-    }
-
 }

dotnet/src/webdriver/Firefox/FirefoxDriverService.cs

@@ -19,10 +19,10 @@
 
 using OpenQA.Selenium.Internal;
 using System;
+using System.Diagnostics;
 using System.Globalization;
 using System.IO;
 using System.Text;
-using System.Threading;
 using OpenQA.Selenium.Internal.Logging;
 
 namespace OpenQA.Selenium.Firefox;
@@ -196,11 +196,11 @@ protected override string CommandLineArguments
     }
 
     /// <summary>
-    /// Handles the event when the driver service process is starting.
+    /// Called when the driver process is starting. This method sets up log file writing if a log path is specified.
     /// </summary>
     /// <param name="eventArgs">The event arguments containing information about the driver service process.</param>
     /// <remarks>
-    /// This method initializes a log writer if a log path is specified and redirects output streams to capture logs.
+    /// This method initializes a log writer if a log path is specified.
     /// </remarks>
     protected override void OnDriverProcessStarting(DriverProcessStartingEventArgs eventArgs)
     {
@@ -214,46 +214,37 @@ protected override void OnDriverProcessStarting(DriverProcessStartingEventArgs e
             }
 
             logWriter = new StreamWriter(this.LogPath, append: true) { AutoFlush = true };
-
-            eventArgs.DriverServiceProcessStartInfo.RedirectStandardOutput = true;
-            eventArgs.DriverServiceProcessStartInfo.RedirectStandardError = true;
         }
 
         base.OnDriverProcessStarting(eventArgs);
     }
 
     /// <summary>
-    /// Handles the event when the driver process has started.
+    /// Handles the output and error data received from the driver process and sends it to the log writer if available.
     /// </summary>
-    /// <param name="eventArgs">The event arguments containing information about the started driver process.</param>
-    /// <remarks>
-    /// This method reads the output and error streams asynchronously and writes them to the log file if available.
-    /// </remarks>
-    protected override void OnDriverProcessStarted(DriverProcessStartedEventArgs eventArgs)
+    /// <param name="sender">The sender of the event.</param>
+    /// <param name="args">The data received event arguments.</param>
+    /// <param name="isError">A value indicating whether the data received is from the error stream.</param>
+    protected override void OnDriverProcessDataReceived(object sender, DataReceivedEventArgs args, bool isError)
     {
-        if (!string.IsNullOrEmpty(this.LogPath) && eventArgs.StandardOutputStreamReader != null)
+        if (string.IsNullOrEmpty(args.Data))
+            return;
+
+        if (!string.IsNullOrEmpty(this.LogPath))
         {
-            var stdoutThread = new Thread(() => ReadStream(eventArgs.StandardOutputStreamReader))
+            if (logWriter != null)
             {
-                IsBackground = true,
-                Name = "FirefoxDriverService-stdout"
-            };
-            stdoutThread.Start();
+                logWriter.WriteLine(args.Data);
+                logWriter.Flush();
+            }
         }
-
-        if (!string.IsNullOrEmpty(this.LogPath) && eventArgs.StandardErrorStreamReader != null)
+        else
         {
-            var stderrThread = new Thread(() => ReadStream(eventArgs.StandardErrorStreamReader))
-            {
-                IsBackground = true,
-                Name = "FirefoxDriverService-stderr"
-            };
-            stderrThread.Start();
+            base.OnDriverProcessDataReceived(sender, args, isError);
         }
-
-        base.OnDriverProcessStarted(eventArgs);
     }
 
+
     /// <summary>
     /// Disposes of the resources used by the <see cref="FirefoxDriverService"/> instance.
     /// </summary>
@@ -353,17 +344,4 @@ private static string FirefoxDriverServiceFileName()
 
         return fileName;
     }
-
-    private void ReadStream(StreamReader reader)
-    {
-        string line;
-        while ((line = reader.ReadLine()) != null)
-        {
-            if (logWriter != null)
-            {
-                logWriter.WriteLine(line);
-                logWriter.Flush();
-            }
-        }
-    }
 }