Cpu 100% when generating pdf again after a restart about wkhtmltopdf-dotnet

[evenlee]

sorry, my fault, I researched my code, seems there is memory leaking.

I changed code from

        var converter = new SynchronizedConverter(new PdfTools());
        var bytes = converter.Convert(doc);
        var provider = new FileExtensionContentTypeProvider();
        var fileName = $"Report_{DateTime.Now.ToString("yyyy-MM-dd_hh-mm-ss")}.pdf";
        var contentType = string.Empty;
        if (!provider.TryGetContentType(fileName, out contentType))
        {
            contentType = "application/octet-stream";
        }
        var stream = new MemoryStream(bytes);
        return new FileStreamResult(stream, contentType)
        {
            FileDownloadName = fileName
        };

to

        using (var converter = new SynchronizedConverter(new PdfTools()))
        {
            var bytes = converter.Convert(doc);
            var provider = new FileExtensionContentTypeProvider();
            var fileName = $"Report_{DateTime.Now.ToString("yyyy-MM-dd_hh-mm-ss")}.pdf";
            var contentType = string.Empty;
            if (!provider.TryGetContentType(fileName, out contentType))
            {
                contentType = "application/octet-stream";
            }
            var stream = new MemoryStream(bytes);
            return new FileStreamResult(stream, contentType)
            {
                FileDownloadName = fileName
            };
        }

the issue has been fixed.

[evenlee]

Thanks for your advice @HakanL, I changed it to global, and the cpu load is improved a bit, and works more smoothly.

[HakanL]

It will be a lot slower if you instantiate the converter in each call. So the recommendation is to have it globally like you posted above. It should be a singleton as you should only have one single instance, the native library is not multi-threaded.

[HakanL]

You should have the converter global in your project, you shouldn't instantiate it for each request.

[wapenshaw]

@HakanL @evenlee Even I am having a similar issue as evenlee, how ever this happens on an azure linux webapp and randonly the CPU usage hits 100 and stays there. Restarting the web app is the only issue .

var converter = new SynchronizedConverter(new PdfTools());
				var doc = new HtmlToPdfDocument
				{
					GlobalSettings =
					{
						ColorMode = ColorMode.Color,
						Orientation = Orientation.Portrait,
						PaperSize = PaperKind.A4,
					},
					Objects =
					{
						new ObjectSettings
						{
							PagesCount = true,
							HtmlContent = outputAsString,
							WebSettings = {DefaultEncoding = "utf-8"},
							HeaderSettings = {FontSize = 9, Right = "Page [page] of [toPage]", Line = true, Spacing = 2.812}
						}
					}
				};
				
					var pdfBytes = converter.Convert(doc);
					var pdfStream = new MemoryStream(pdfBytes);
					var pdfFileResult = new FileStreamResult(pdfStream, "application/pdf");
					var pdfName = $"HMRC_MTD_VAT_RETURN_{periodKey}.pdf";
					pdfFileResult.FileDownloadName = pdfName;

					return pdfFileResult;

This is my code, I will try using the using keyword to properly use the IDisposable instance and update the situation. Meanwhile can you explain what You should have the converter global in your project meant?

[HakanL]

Having the converter global means you don't instantiate it on each call, but have one shared instance throughout your application.

[wapenshaw]

@HakanL Thank you, in my case thats the only place I use the PDF converter, adding the using statement fixed my issue. So thank you for that too! but I understand having global instance, I have implemented something like this in my project.

https://github.com/JakeSiewJK64/SWE20001/blob/e4bd84f7de659340fc7ee85aa1a0034687613868/src/Infrastructure/DependencyInjection.cs#L69

https://github.com/JakeSiewJK64/SWE20001/blob/e4bd84f7de659340fc7ee85aa1a0034687613868/src/Infrastructure/PDF/PDFConverterHelper.cs#L7

services.AddSingleton(typeof(IConverter), new SynchronizedConverter(new PdfTools()));
services.AddTransient<IPdfGenerator, PdfGenerator>();

and I am using the PdfGenerator across my application now. Do you suggest Injecting the PDF Service as a Transient one or Scoped one?