.NET DriverService improvment to check response on startup

With this commit, a driver using a driver service will now throw a
WebDriverException if it cannot start the driver service, or if the
service executable returns an invalid response. Note that the checks
for the validation of the repsonses is minimal, checking for the
Content-Type header and that the repsonse code is a 200.

Signed-off-by: Jim Evans <[email protected]>

Author: livioc

Diff for: dotnet/src/webdriver/DriverService.cs

@@ -17,14 +17,11 @@
 // </copyright>
 
 using System;
-using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
 using System.Net;
-using System.Net.Sockets;
 using System.Security.Permissions;
-using System.Text;
 using OpenQA.Selenium.Internal;
 using OpenQA.Selenium.Remote;
 
@@ -181,23 +178,40 @@ public void Start()
             this.driverServiceProcess.StartInfo.UseShellExecute = false;
             this.driverServiceProcess.StartInfo.CreateNoWindow = this.hideCommandPromptWindow;
             this.driverServiceProcess.Start();
-            Uri serviceHealthUri = new Uri(this.ServiceUrl, new Uri("status", UriKind.Relative));
+            Uri serviceHealthUri = new Uri(this.ServiceUrl, new Uri(DriverCommand.Status, UriKind.Relative));
             bool processStarted = false;
             DateTime timeout = DateTime.Now.Add(TimeSpan.FromSeconds(20));
             while (!processStarted && DateTime.Now < timeout)
             {
                 try
                 {
+                    // If the driver service process has exited, we can exit early.
+                    if (this.driverServiceProcess.HasExited)
+                    {
+                        break;
+                    }
+
                     HttpWebRequest request = HttpWebRequest.Create(serviceHealthUri) as HttpWebRequest;
                     request.KeepAlive = false;
                     HttpWebResponse response = request.GetResponse() as HttpWebResponse;
+
+                    // Checking the response from the 'status' end point. Note that we are simply checking
+                    // that the HTTP status returned is a 200 status, and that the resposne has the correct
+                    // Content-Type header. A more sophisticated check would parse the JSON response and
+                    // validate its values. At the moment we do not do this more sophisticated check.
+                    processStarted = response.StatusCode == HttpStatusCode.OK && response.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase);
                     response.Close();
-                    processStarted = true;
                 }
                 catch (WebException)
                 {
                 }
             }
+
+            if (!processStarted)
+            {
+                string msg = "Cannot start the driver service on " + this.ServiceUrl;
+                throw new WebDriverException(msg);
+            }
         }
 
         /// <summary>