Windows service crashes - Magick.NET Q16 HDRI x64

[edgarbidmail]

Setup

• .NET Framework 4.8
• C#
• Magick.NET Q16 HDRI x64 14.9.0
• Ghostscript
  • 9.54.0 -- works fine
  • 10.03.1 -- not working
  • 10.06.0 -- not working
• OS -- Windows Server 2012 r2

I have an app running as a windows service in a Windows Server 2012 r2 server. The app reads a pdf file from a network and then creates tiles from each page to feed a deep zoom service.

Recently, a set of pdf files are causing the service to crash completely. Every part of the code is properly coded inside try catch blocks and any error gets logged back to a db.

The pdf file opens fine using Acrobat reader and I just don't see anything wrong with it, the only difference I see is that the files contains an unusually large amount of keywords in the meta data. Attached a sample file.
200-24946866.PDF

The error is being thrown in the following block of code:
try {
using (images = new MagickImageCollection())
{
// Read all the pages of the pdf to the collection.
images.Read(_stream, settings);
...
}
}
catch...

When the code eraches the line images.Read(_stream, settings);, the app throws the following error.
Attempted to read or write protected memory. This is often an indication that other memory is corrupt

This error happens when using Ghostcript versions: 10.03.1 and 10.06.0, but it works fine with version 9.54.0.
After testing, every version of Ghostscript starting from 9.55.0 FAILS!!
I read version 9.55.0 introdueces a new pdf interpreter written en C instead of PostScript, but it is disabled by default.

I would very much appreciate any help to find out:

1. Why am I getting that memory error
2. Why is that the error not getting caught by the try catch, killing the entire service

Any help will be awesome!
Edgar Landazuri

[dlemstra]

Which version of this library are you using?

[edgarbidmail]

Woops, sorry, I forgot to add the number in the Setup section of my original post. I am using Magick.NET Q16 HDRI x64 v14.9.0.
Thanks in advance!!

Edgar Landazuri

[dlemstra]

I am unable to reproduce your issue by guessing the rest of the code from your example. Please provide a complete and small example that can be used to reproduce the issue.

[edgarbidmail]

Working on it!!

[edgarbidmail]

After creating a trimmed down version of the app, the dev team was able to find the exact line causing the problem. We declare a MagickReadSettings and set the Density to a value of 200. We just tried using values of 100 and 150 and it worked fine, any greater value will just fail.
int dpi = 200;
var defines = new PdfReadDefines() { Interpolate = true };
var settings = new MagickReadSettings();

settings.Density = new Density(dpi); **// This line is the one causing the issue.**

settings.Compression = CompressionMethod.NoCompression;
settings.Format = MagickFormat.Pdf;
settings.StrokeAntiAlias = true;
settings.TextAntiAlias = true;

Attached you'll find a zip file with a VS 2022 solution
MagickService1.zip https://drive.google.com/file/d/1qvoh5VpmY5qyaS0KmT0T4QrJjXd_O4PP/view?usp=sharing

• MagickLibrary
  • Class1.cs - Here is the main function ProcessFile
• MagickTest
  • UnitTest1.cs - You'll find a test method here, just make sure to pass the correct values for the file path and the ghostcript file path
• WindowsService1
  • Service.cs [not in design view] - You'll find the start point at method OnStart, just make sure to pass the correct values for the file path and the ghostcript file path

Some notes:

• Density settings is causing the issue, we usually set it at 200 dpi, I don't know if there is a recommended way to set this value up, but the 200 has been working fine for a long time, except for the sample file I provided.
• Same settings work fine with ghostcript v 9.54.0

Questions

• @dlemstra do you happen to know why is that dpi value failing for the sample file?
• I still wonder why, when the app is deployed as a service, the error crashes the service completely instead of getting caugth by the try catch block.

Any help will be greatly appreciated.
Edgar Landazuri

[dlemstra]

I am happy to hear that you have figured out how it can be reproduced. But please make this easy for me to investigate. I only need two files. A .csproj file and a Program.cs file that demonstrates the issue in a command line application.

[edgarbidmail]

Happy to!!

During this new attempt we stumbled upon yet another discovery. The error changes depending what type of library we are using, in this case we tested with the Magick.NET Q16 HDRI x64 14.9.0 and the Magick.NET Q16 HDRI AnyCPU 14.9.0 and we saw the following:

• Magick.NET Q16 HDRI x64 14.9.0 -- throws the error and kills the console app, the error is the memory issue one
• Magick.NET Q16 HDRI AnyCPU 14.9.0 -- throws the error but the error gets caught by the try catch block, the error is different and related to the ghostcript command

Attached both zip files
ConsoleApp1-x64.zip
ConsoleApp1-AnyCPU.zip
The zip files contain only what @dlemstra you requested, a .crsproj file and a Program.cs

After this discovery I realized we are using x64 version of the library because our servers are x64 architecture, but maybe we have it wrong, maybe we could use the any cpu version. The error is still happening in both versions, so not a priority topic UNLESS you recommend to use one version over the other.

Quoted the same notes and questions from before

Some notes:
Density settings is causing the issue, we usually set it at 200 dpi, I don't know if there is a recommended way to set this value up, but the 200 has been working fine for a long time, except for the sample file I provided.
Same settings work fine with ghostcript v 9.54.0
Questions

@dlemstra do you happen to know why is that dpi value failing for the sample file?
I still wonder why, when the app is deployed as a service, the error crashes the service completely instead of getting caugth by the try catch block.

As before, any help is greatly appreciated
Edgar Landazuri

[dlemstra]

Thanks for continuing to provide me with the requested information. This really safes me a lot of time on all the support I am providing to you. The good news is that I figured out what is happening. When reading that PDF file with those specific settings you are running into an access violation inside the Ghostscript library. The Ghoscript library can be started in two different ways. It can either be loaded directly into memory or a command is executed on the command line. You seem to be running your application in 64-bit and I would recommend you to do that because it allows you to allocate more memory. When both Ghostscript and your application are 64-bit the Ghoscript library will be loaded in your application. But when an access violation happens this also means that this access violation is happening "inside" your application and that means the whole application will be terminated. When you run your service in 32-bit it will execute the application on the command line and when the access violation happens this will only terminate the Ghostscript application. The bad news is that I cannot help you any further because this is happening inside the Ghostscript library. The only thing that I could do would be to introduce an option that would prevent loading the Ghoscript library into the application and force it it always use the command line instead.