Duplicating File Uploading Process - Asp.net WebApi - azure

Question

I created a web API which allows users to send files and upload to Azure Storage. The way it works is, the client app will connect to API to send one or more files to the file upload controller and controller will take care of rest such as
Upload file to Azure storage
Update database
Works great but I don't think it is the right way to do this because now I can see there are two different processes
Upload file from the client's file system to my web API (server)
Upload file to the Azure storage from API (server)
It gives me the feeling that I am duplicating the upload process as the same file first travels to API (server) and then Azure (destination) from the client (file system). I feel the need of showing two progress-bars to the client for file upload progress (from client to server and then the server to Azure) - That just doesn't make sense to me and I feel that my approach is incorrect.
My API accepts up to 250MBs so you can imagine the overload.
What do you guys think?
//// API Controller
if (!Request.Content.IsMimeMultipartContent("form-data"))
{
throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
}
var provider = new RestrictiveMultipartMemoryStreamProvider();
var contents = await Request.Content.ReadAsMultipartAsync(provider);
int Total_Files = contents.Contents.Count();
foreach (HttpContent ctnt in contents.Contents)
{
await storageManager.AddBlob(ctnt)
}
////// Stream
#region SteamHelper
public class RestrictiveMultipartMemoryStreamProvider : MultipartMemoryStreamProvider
{
public override Stream GetStream(HttpContent parent, HttpContentHeaders headers)
{
var extensions = new[] { "pdf", "doc", "docx", "cab", "zip" };
var filename = headers.ContentDisposition.FileName.Replace("\"", string.Empty);
if (filename.IndexOf('.') < 0)
return Stream.Null;
var extension = filename.Split('.').Last();
return extensions.Any(i => i.Equals(extension, StringComparison.InvariantCultureIgnoreCase))
? base.GetStream(parent, headers)
: Stream.Null;
}
}
#endregion SteamHelper
///// AddBlob
public async Task<string> AddBlob(HttpContent _Payload)
{
CloudStorageAccount cloudStorageAccount = KeyVault.AzureStorage.GetConnectionString();
CloudBlobClient cloudBlobClient = cloudStorageAccount.CreateCloudBlobClient();
CloudBlobContainer cloudBlobContainer = cloudBlobClient.GetContainerReference("SomeContainer");
cloudBlobContainer.CreateIfNotExists();
try
{
byte[] fileContentBytes = _Payload.ReadAsByteArrayAsync().Result;
CloudBlockBlob blob = cloudBlobContainer.GetBlockBlobReference("SomeBlob");
blob.Properties.ContentType = _Payload.Headers.ContentType.MediaType;
blob.UploadFromByteArray(fileContentBytes, 0, fileContentBytes.Length);
var B = await blob.CreateSnapshotAsync();
B.FetchAttributes();
return "Snapshot ETAG: " + B.Properties.ETag.Replace("\"", "");
}
catch (Exception X)
{
return ($"Error : " + X.Message);
}
}

Answer 1

It gives me the feeling that I am duplicating the upload process as
the same file first travels to API (server) and then Azure
(destination) from the client (file system).
I think you're correct. One possible solution would be have your API generate a Shared Access Signature (SAS) token and return that SAS token/URI to the client whenever a client wishes to upload a file.
Using this SAS URI your client can directly upload the file to Azure Storage without sending it to your API first. Once the file is uploaded successfully by the client, it can send a message to the API to update the database.
You can read more about SAS here: https://learn.microsoft.com/en-us/azure/storage/common/storage-dotnet-shared-access-signature-part-1.
I have also written a blog post long time back on using SAS that you may find useful: https://gauravmantri.com/2013/02/13/revisiting-windows-azure-shared-access-signature/.