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I'm trying to download binary files from my Azure storage account. Initially, I was using CloudBlob.DownloadToFileAsync() which allowed me to supply a IProgress parameter and get progress updates of the transfer.

However, on bigger > 2gb files, DownloadToFileAsync was hanging. According to the documentation I needed to be using DownloadToFileParallelAsync to download larger files. I have implemented this, and confirm it now works, but now I'm unable to get the progress of the download as it does not offer a IProgress parameter.

https://learn.microsoft.com/en-us/dotnet/api/microsoft.azure.storage.blob.cloudblob.downloadtofileparallelasync?view=azure-dotnet-legacy

Can anyone point me to how I can gather any useful progress data, or offer a workaround?

            int parallelIOCount = SystemInfo.processorCount;
            long rangeSizeInBytes = 16 * Constants.MB;
            await cloudModuleBlob.DownloadToFileParallelAsync(targetTempModuleFile, FileMode.Create, parallelIOCount, rangeSizeInBytes, cancellationTokenSource.Token);

            progressSlider.value = 1.0f;


            //When the download is finished...
            //Rename the temp file to the full version.
            if (File.Exists(targetCiqModuleFile))
            {
                File.Delete(targetCiqModuleFile);
            }

            File.Move(targetTempModuleFile, targetCiqModuleFile);



            Debug.Log("Download saved to: " + targetCiqModuleFile);
PhullivanCuriious
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  • 2

1 Answers1

0

Solved it with a workarounnd. Rather than using DownloadToFileAsync I instead used DownloadRangeToStreamAsync to break the blob into smaller pieces and combined them on the client end. Works effectively with 16mb chunks.

            //Create the file.
            using (FileStream fileStream = File.Create(targetTempModuleFile))
            {

                long chunkSize = 16 * Constants.MB;

                Int64 current = 0;

                while (current < cloudModuleBlob.Properties.Length)
                {


                    if ((current + chunkSize) > cloudModuleBlob.Properties.Length)
                    {
                        await cloudModuleBlob.DownloadRangeToStreamAsync(fileStream, current, (cloudModuleBlob.Properties.Length - current), default, default, default, progressHandler, cancellationToken);
                    }
                    else
                    {
                        await cloudModuleBlob.DownloadRangeToStreamAsync(fileStream, current, chunkSize, default, default, default, progressHandler, cancellationToken);
                    }


                    current = current + chunkSize;

                }
                
               
            }
PhullivanCuriious
  • 11
  • 2