First Call from .Net core 2.1, subsequent request hangs

[Raghav-Gowda]

Hello,

I am working on ASP.NET Core v2.1.
I am able to generate PDF for the first time, but subsequent request hangs.
Please note, I've declare SynchronizedConverter as singleton in Startup.cs

        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

        services.AddDbContext<OCDBContext>(options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

        services.AddSingleton(typeof(IConverter), new SynchronizedConverter(new PdfTools()));

        services.AddMvc().AddSessionStateTempDataProvider();
        services.AddSession();

Please suggest how to solve this issue.

[MagnusJohansson]

I am having the same problem.
Have you found any solution?

It can easily be reproduced in a console app as well, the second iteration in the loop below, the conversion will hang:

    static void Main(string[] args)
        {
            var doc = new HtmlToPdfDocument()
            {
                GlobalSettings =
                {
                    ColorMode = ColorMode.Color,
                    Orientation = Orientation.Portrait,
                    PaperSize = PaperKind.A4,
                },
                Objects =
                {
                    new ObjectSettings()
                    {
                        PagesCount = true,
                        HtmlContent = @"Lorem ipsum dolor sit amet",
                        WebSettings =
                        {
                            DefaultEncoding = "utf-8"
                        },
                        HeaderSettings =
                        {
                            FontSize = 9, Right = "Page [page] of [toPage]", Line = true, Spacing = 2.812
                        }
                    }
                }
            };

            for (int i = 0; i < 2; i++)
            {
                var converter = new SynchronizedConverter(new PdfTools());
                byte[] pdfData = converter.Convert(doc);
            }

        }

[MagnusJohansson]

One possible workaround can be to instantiate a new BasicConverter for each request and force the PdfTools object to dispose and unload the libraries after each request in a ASP.NET controller, like this:

[Produces(MediaTypeNames.Application.Pdf)]
public async Task<IActionResult> Index()
{
    var doc = new HtmlToPdfDocument()
    {
        GlobalSettings =
        {
            ColorMode = ColorMode.Color,
            Orientation = Orientation.Portrait,
            PaperSize = PaperKind.A4,
        },
        Objects =
        {
            new ObjectSettings()
            {
                PagesCount = true,
                HtmlContent = @"Lorem ipsum dolor sit amet, consectetur adipiscing elit. In consectetur mauris eget ultrices  iaculis.",
                WebSettings = { DefaultEncoding = "utf-8" },
                HeaderSettings = { FontSize = 9, Right = "Page [page] of [toPage]", Line = true, Spacing = 2.812 }
            }
        }
    };
            
    using (var tools = new PdfTools())
    {
        var converter = new BasicConverter(tools);
        byte[] pdfData = converter.Convert(doc);
        return File(pdfData, MediaTypeNames.Application.Pdf);
    }
}

[MagnusJohansson]

I spoke too soon.
This is not a valid work around because;

• If using singleton instances of PdfTools and a Converter, DinkToPdf hangs on subsequent calls
• If instantiating a new PdfTools for every request, the first creation is ok, but any subsequent conversions looses the HTML generation Subsequent PdfTools instances yield wrong PDF output #44 , only plain text is rendered .

What a mess this is.

[mze9412]

It seems to work for me after switching to the newest version of wkhtmltopdf (see also this PR)
#59

[HakanL]

I upgraded to 0.12.5 of the 64-bit Windows library and it still hangs on the second request, so PR #59 didn't help me. However, I realized I was creating multiple instances of SynchronizedConverter, once I changed to a singleton then it actually works fine.

[caldus85]

I upgraded to 0.12.5 of the 64-bit Windows library and it still hangs on the second request, so PR #59 didn't help me. However, I realized I was creating multiple instances of SynchronizedConverter, once I changed to a singleton then it actually works fine.

This fixed the issue for me. Thanks!

[Alexander-Lazarov88]

If someone still has this issue, can try to remove this 'var converter = new SynchronizedConverter(new PdfTools());' and just inject 'IConverter' in your service. I try and this approach is working, after all, we already register the converter, we don`t need to create an instance with 'new' keyword.

[asimon91]

I confirm too that changing to singleton instead of multiple instances works flawlessly. Thank you!

[renatolopes]

When i call in the integration tests, in second test that calls convert i'm with same issue even follow the instructions and using singleton injection. Any tips?

[caldus85]

When i call in the integration tests, in second test that calls convert i'm with same issue even follow the instructions and using singleton injection. Any tips?

I would try version 0.12.5 above if you are not already. Then double check that you're calling services.AddSingleton(typeof(IConverter), new SynchronizedConverter(new PdfTools()));. Also note Alexander-Lazarov88's comment above about possibly using IConverter instead. Beyond that I don't have any other ideas, sorry.

[zbex]

When i call in the integration tests, in second test that calls convert i'm with same issue even follow the instructions and using singleton injection. Any tips?

Any luck with this? I experience the same issue.