Executing a process on IIS makes RAM goes up really quick

Question

I built an ASP.NET MVC API hosted on IIS on Windows 10 Pro (VM on Azure - 4GB RAM, 2CPU). Within I call an .exe (wkhtmltopdf) that I want to convert an HTML page to image and save it locally. Everything works fine, except I noticed that after some calls to the API, the RAM goes crazy and while investigating the process with Task Manager I saw a process, called IIS Worker Process, that adds more RAM every time the API is called. Of course I wrapped my System.Diagnostics.Process instance usage inside a using statement to be disposed, because IDisposable is implemented, but it still consumes more and more RAM and after a while the server becomes laggy and unresponsive (it has only 4GB of RAM after all). I noticed that after some number of minutes (10-15-20 maybe) this IIS Worker Process calms down in terms of RAM usage... Here is my code, pretty straight forward:

1. Gets base64 encoded url
2. Decodes it
3. Uses wkhtmltoimage.exe to convert it to image
4. Saves it locally
5. Reads the byte array
6. Creates a blob in Azure with the image

7. Returns json with the url

   public async Task<ActionResult> Index(string url)
   {
       object oJSON = new { url = string.Empty };
   
       if (!string.IsNullOrEmpty(value: url))
       {
           try
           {
               byte[] EncodedData = Convert.FromBase64String(s: url);
               string DecodedURL = Encoding.UTF8.GetString(bytes: EncodedData);
   
               using (Process proc = new Process())
               {
                   proc.StartInfo.FileName = wkhtmltopdfExecutablePath;
                   proc.StartInfo.Arguments = $"--encoding utf-8 \"{DecodedURL}\" {LocalImageFilePath}";
                   proc.Start();
                   proc.WaitForExit();
   
                   oJSON = new { procStatusCode = proc.ExitCode };
               }
   
               if (System.IO.File.Exists(path: LocalImageFilePath))
               {
                   byte[] pngBytes = System.IO.File.ReadAllBytes(path: LocalImageFilePath);
   
                   System.IO.File.Delete(path: LocalImageFilePath);
   
                   string ImageURL = await CreateBlob(blobName: $"{BlobName}.png", data: pngBytes);
   
                   oJSON = new { url = ImageURL };
               }
           }
           catch (Exception ex)
           {
               Debug.WriteLine(value: ex);
           }
       }
   
       return Json(data: oJSON, behavior: JsonRequestBehavior.AllowGet);
   }
   
   private async Task<string> CreateBlob(string blobName, byte[] data)
   {
       string ConnectionString = "DefaultEndpointsProtocol=https;AccountName=" + AzureStorrageAccountName + ";AccountKey=" + AzureStorageAccessKey + ";EndpointSuffix=core.windows.net";
       CloudStorageAccount cloudStorageAccount = CloudStorageAccount.Parse(connectionString: ConnectionString);
       CloudBlobClient cloudBlobClient = cloudStorageAccount.CreateCloudBlobClient();
       CloudBlobContainer cloudBlobContainer = cloudBlobClient.GetContainerReference(containerName: AzureBlobContainer);
   
       await cloudBlobContainer.CreateIfNotExistsAsync();
   
       BlobContainerPermissions blobContainerPermissions = await cloudBlobContainer.GetPermissionsAsync();
       blobContainerPermissions.PublicAccess = BlobContainerPublicAccessType.Container;
   
       await cloudBlobContainer.SetPermissionsAsync(permissions: blobContainerPermissions);
   
       CloudBlockBlob cloudBlockBlob = cloudBlobContainer.GetBlockBlobReference(blobName: blobName);
       cloudBlockBlob.Properties.ContentType = "image/png";
   
       using (Stream stream = new MemoryStream(buffer: data))
       {
           await cloudBlockBlob.UploadFromStreamAsync(source: stream);
       }
   
       return cloudBlockBlob.Uri.AbsoluteUri;
   }
   

Here are the resources I'm reading somehow related to this issue IMO, but are not helping much:

Investigating ASP.Net Memory Dumps for Idiots (like Me)

ASP.NET app eating memory. Application / Session objects the reason?

IIS Worker Process using a LOT of memory?

Run dispose method upon asp.net IIS app restart

IIS: Idle Timeout vs Recycle

UPDATE:

if (System.IO.File.Exists(path: LocalImageFilePath))
{
    string BlobName = Guid.NewGuid().ToString(format: "n");
    string ImageURL = string.Empty;

    using(FileStream fileStream = new FileStream(LocalImageFilePath, FileMode.Open)
    {
        ImageURL = await CreateBlob(blobName: $"{BlobName}.png", dataStream: fileStream);
    }

    System.IO.File.Delete(path: LocalImageFilePath);

    oJSON = new { url = ImageURL };
}

Answer 1

The most likely cause of your pain is the allocation of large byte arrays:

byte[] pngBytes = System.IO.File.ReadAllBytes(path: LocalImageFilePath);

The easiest change to make, to try and encourage the GC to collect the Large Object Heap more often, is to set GCSettings.LargeObjectHeapCompactionMode to CompactOnce at the end of the method. That might help.

But, a better idea would be to remove the need for the large array altogether. To do this, change:

private async Task<string> CreateBlob(string blobName, byte[] data)

to instead be:

private async Task<string> CreateBlob(string blobName, FileStream data)

And then later use:

await cloudBlockBlob.UploadFromStreamAsync(source: data);

In the caller, you'll need to stop using ReadAllBytes, and instead use a FileStream to read the file instead.