Async/await, Task Parallel 对于在调试时运行 FINE 但没有运行失败的复杂进程

Question

I am trying to execute a very complex operation parallely with TPL For. It has API calling with async/await and with selenium webdriver.

When I debug the application, it runs smoothly, but when I run it without debugger, it crashes shortly and following message shows.

{System.OutOfMemoryException: Out of memory.
   at System.Drawing.Bitmap.Clone(Rectangle rect, PixelFormat format)
   at Browser_Automation.Parser.CropImage(Bitmap source, Rectangle section) in E:\Work\XXXXX\XXXXX\XXXXX Automation\JSON\SuiteParser.cs:line 598
   at XXXXX.Parser.GetCaptchaById(IWebDriver driver, String id) in E:\Work\XXXXX\XXXXX\XXXXXAutomation\JSON\SuiteParser.cs:line 577
   at Browser_Automation.Parser.<GetFirstCaptchaUrl>d__23.MoveNext() in E:\Work\XXXXX\XXXXX\XXXXXAutomation\JSON\SuiteParser.cs:line 526
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Browser_Automation.Parser.<_Execute>d__27.MoveNext() in E:\Work\SupportKing\VisaBot\Browser Automation\JSON\SuiteParser.cs:line 646}

Here is the code, where it indicates the bitmap memory out ....

private string GetCaptchaById(IWebDriver driver, string id)
    {
        //Getting the image, which is in this case has a url as source.
        var captcha_image = driver.FindElement(By.Id(id));
        string resultBase64 = "";
        if (captcha_image != null)
        {

            try
            {
                //Deleting previous screenshot images from the folder
                System.IO.DirectoryInfo di = new DirectoryInfo(App.Directory.FullName + "\\ScreenshotImages");
                foreach (FileInfo file in di.GetFiles())
                {
                    file.Delete();
                }
            }
            catch (Exception ex)
            {
            }


            var path1 = App.Directory.FullName + "\\ScreenshotImages\\" + Guid.NewGuid().ToString() + ".png";

            //Creating screenshot of the full web page and saving it to the path
            ITakesScreenshot ssdriver = driver as ITakesScreenshot;
            Screenshot screenshot = ssdriver.GetScreenshot();
            Screenshot tempImage = screenshot;
            tempImage.SaveAsFile(path1, ScreenshotImageFormat.Png);

            //Creating a rectangle of same size as the captcha
            Point point = captcha_image.Location;
            point.X = point.X;
            point.Y = point.Y;
            int width = captcha_image.Size.Width;
            int height = captcha_image.Size.Height;
            Rectangle section = new Rectangle(point, new System.Drawing.Size(width, height));

            //Loding the full page image from the path
            Bitmap fullImg = new Bitmap(path1);

            //creating a new image as the same width height of the captcha
            Bitmap source = new System.Drawing.Bitmap(width, height);

            //This is the final captcha image. We are croping the captcha image from the full image with location(X,Y) and size(W,H)
            Bitmap final_image = CropImage(fullImg, section);

           resultBase64 = ConvertBitmapToBase64(final_image);
            //final_image.Save(@"E:\\out.jpg");
        }

        return resultBase64;
    }

And it is the line where its catching the error :

Screenshot screenshot = ssdriver.GetScreenshot();

Answer 1

Here are a couple of things:

1. Don't mix Parallel.For with async and await. It's not suited to work with the async and await pattern.
2. Your exception is most definitely caused by running out of GDI memory because you are not disposing all your Bitmaps .

System.OutOfMemoryException: Out of memory. at System.Drawing.Bitmap.Clone(Rectangle rect, PixelFormat format)

Put all your bitmaps into a using statement .

Or call Dispose immediately after you have finished with them.

Answer 2

implement try catch to find out where (possible before the line 598) out of memory, the variable may still occupied memory. You can able to try GC.Collect(), specific generations if you know what you want to release, if solved can removed, effect performance of suspend you app in thread.