Asynchronous File Validation Method Not Responding in Docker Environment

Question

I'm working on an ASP.NET Core application running inside a Docker container. I have an API endpoint that processes a file asynchronously. The method picks a pending file, triggers an async validation process in a separate thread, and then immediately returns a response. However, when running inside Docker, I don't see any response after setting result.Data. The request just hangs.

below is the Sample code,

[Route("ProcessFile"), HttpPost]
public async Task<ApiResponse> ProcessFile(long id)
{
    ApiResponse response = new ApiResponse();
    List<FileLog> pendingFiles = _fileLogService.GetWhere(x => x.Status == 0).OrderBy(x => x.CreatedDate).ToList();
    FileLog selectedFile = new FileLog();
    
    try
    {
        if (pendingFiles != null && pendingFiles.Count > 0)
        {
            // Select the file matching the given ID
            selectedFile = pendingFiles.FirstOrDefault(f => f.FileId.ToString().EndsWith(id.ToString()));

            if (selectedFile != null)
            {
                List<FileLog> filesToProcess = new List<FileLog> { selectedFile };
                
                Console.WriteLine("Starting async validation process...");
                
                Task.Run(async () => await ValidateFileAsync(filesToProcess));

                response.Message = $"File {selectedFile.FileName} (ID: {selectedFile.FileId}) picked for validation.";
                response.Success = true;
            }
            else
            {
                response.Message = $"No pending file found with ID ending in {id}.";
                response.Success = false;
            }
        }
        else
        {
            response.Message = "No pending files available for validation.";
            response.Success = false;
        }
    }
    catch (Exception ex)
    {
        _logger.LogError(ex, "Error while processing file validation");
        response.Message = $"Failed to process file with ID: {selectedFile.FileId}";
        response.Success = false;
    }

    return response;
}

The method works perfectly in UAT Docker but hangs in Production Docker after setting response.Message.
No error logs are seen in the production pod logs.
No exception is thrown in the API, and nothing is logged after response.Message.
The ValidateFileAsync() method is supposed to run in the background, and the API should return immediately, but that doesn’t happen in Production.

Additional Context:

In Production, we trigger this API via a Task Scheduler running on an app server.
The Task Scheduler logs confirm that it receives this response:

result.Data = "The file - {selectedFile.FileName} having File ID: {selectedFile.FileId} is picked for processing validations."

But after this point, the method doesn't continue execution in Production.

Question:

Why does this behavior occur only in Docker and not in my local environment?
Could this be related to how Task.Run behaves in a containerized environment?
Is there a better way to handle background processing in ASP.NET Core hosted in Docker?

The most likely cause is that ValidateFileAsync throws an exception. But since you run it asynchronously in a 'fire and forget' manner, any exceptions it throws are lost and not logged. Try doing just await ValidateFileAsync(filesToProcess) with no Task.Run. — Hans Kilian
– Hans Kilian, Commented Mar 21 at 8:11
Wouldn't await limit parallelism since Task.Run allows multiple files to process concurrently? — nishant bhadke
– nishant bhadke, Commented Mar 21 at 9:56
Right now your issue is that it fails without logging why. You can add the Task.Run back again when you've found out why. — Hans Kilian
– Hans Kilian, Commented Mar 21 at 10:09
Appreciate the input, Also your suggestion helped with debugging. Thanks! — nishant bhadke
– nishant bhadke, Commented Mar 23 at 8:30

nishant bhadke · Accepted Answer · 2025-03-23 08:29:34Z

0

I debugged by scaling down the pods to 1 and replacing Task.Run with await, but the issue persisted. After an hour of troubleshooting, we found the real culprit—an active trigger on the table.

With .NET 8.0, triggers need explicit handling, or they cause silent exceptions logged only at the console, not in DB or files. This also highlighted gaps in our error logging.

So, Task.Run wasn’t the issue.

answered Mar 23 at 8:29

nishant bhadke

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