Azure function to copy files from FTP to blob storage using FluentFTP

Question

I have an FTP source that adds daily file and I need to copy the files on daily basis from FTP to blob storage using FluentFTP library in azure function

I am using C# in Azure function, and I did all the coding part but missing to download the file from FTP to copy it directly to the blob destination.

//#r "FluentFTP"
#r "Newtonsoft.Json"
#r "System.Data"
#r "Microsoft.WindowsAzure.Storage"

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System.Collections.Generic;
using System.Globalization;
using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using Microsoft.WindowsAzure.Storage;
using Microsoft.WindowsAzure.Storage.Auth;
using Microsoft.WindowsAzure.Storage.Blob;

using System.Net;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Primitives;
using Newtonsoft.Json;
using FluentFTP;

public static async Task<IActionResult> Run(HttpRequest req, ILogger log)
{
    string blobConnectionString = "ConnectionString";

    // Gestione BLOB Storage
    CloudStorageAccount storageAccount = CloudStorageAccount.Parse(blobConnectionString);
    CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
    CloudBlobContainer container = blobClient.GetContainerReference("out");

    using (FtpClient conn = new FtpClient()) 
    {
        conn.Host = "ftp server";
        conn.Credentials = new NetworkCredential("username", "pass");

        // get a list of files and directories in the "/OUT" folder
        foreach (FtpListItem item in conn.GetListing("/OUT")) 
        {
            // if this is a file and ends with CSV
            if (
            item.Type == FtpFileSystemObjectType.File
            &&
            item.FullName.ToLower().EndsWith(".csv")
            )
            {

                string yyyy = item.FullName.Substring(10,4);
                string mm   = item.FullName.Substring(14,2);
                string dd   = item.FullName.Substring(16,2);
                var fileName = "out/brt/" + yyyy + "/"+ mm + "/"+ dd + "/" + item.Name;

                CloudBlockBlob blockBlob = container.GetBlockBlobReference(fileName);
                // download the file
                conn.DownloadFile( blockBlob , item.FullName);
            }
        }

        return new OkObjectResult($"Hello");
    }
}

If I can use a blob container as a destination for the FluentFTP function then it would be the best, but this way I am getting the error that this blob block that I am using is not an a destination

This is the error that I am getting

cannot convert from 'Microsoft.WindowsAzure.Storage.Blob.CloudBlockBlob' to 'string'

I don't know if there is another way to download the file locally so I can upload it to the blob instead of using this client.DownloadFile function.

Answer 1

If you want to use FluentFTP, you can get a blob upload stream using one of these two methods:

1. CloudBlockBlob.OpenWrite()
2. CloudBlockBlob.OpenWriteAsync()

Then you can use the FTPClient.Download method which takes a Stream

public bool Download(Stream outStream, string remotePath, IProgress<double> progress = null)

Something like this:

[FunctionName("HttpTriggerCSharp")]
    public static async Task<IActionResult> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req, ILogger log)
    {
        log.LogInformation("C# HTTP trigger function processed a request.");

        var ftpHost = "xxxxx";
        var ftpUserName = "xxxx";
        var ftpPassword = "xxxx";
        var filename = "xxxxx";            
        string blobConnectionString = "xxxxxxxxxxx";

        CloudStorageAccount storageAccount = CloudStorageAccount.Parse(blobConnectionString);
        CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
        CloudBlobContainer container = blobClient.GetContainerReference("xxxxx");


        FtpClient client = new FtpClient(ftpHost, ftpUserName, ftpPassword); // or set Host & Credentials
        client.EncryptionMode = FtpEncryptionMode.Implicit;
        client.SslProtocols = SslProtocols.None;
        client.ValidateCertificate += new FtpSslValidation(OnValidateCertificate);
        client.Connect();

        void OnValidateCertificate(FtpClient control, FtpSslValidationEventArgs e) {
            // add logic to test if certificate is valid here
            e.Accept = true;
        }

        CloudBlockBlob blockBlob = container.GetBlockBlobReference(filename);
        var outStream = blockBlob.OpenWrite();
        client.Download(outStream,filename);
        outStream.Commit(); // I'm not sure if this is needed?

        log.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}");


        return  (ActionResult)new OkObjectResult($"Action succeeded.");
    }

Answer 2

It's probably not possible with Fluent FTP.

There's FtpClient.Download method which takes Stream .

public bool Download(Stream outStream, string remotePath, IProgress<double> progress = null)

But it does not look like there's API to get "blob upload Stream" .

Conversely, you cannot get "FTP download Stream" from FluentFTP (which you would be able to use with blob API).

---

But you can use native .NET FtpWebRequest FTP client, which has API to get "FTP download Stream" :

public static async System.Threading.Tasks.Task RunAsync([TimerTrigger("0 */1 * * * *")]TimerInfo myTimer, ILogger log)
{
    var ftpUserName = "xxxxxx";
    var ftpPassword = "xxxxxxxxx";
    var filename = "test.png";
    string blobConnectionString = "xxxxxxx";
    CloudStorageAccount storageAccount = CloudStorageAccount.Parse(blobConnectionString);
    CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
    CloudBlobContainer container = blobClient.GetContainerReference("myblobcontainer");
    FtpWebRequest fileRequest = (FtpWebRequest)WebRequest.Create("ftp://xxxxxx/" + filename);
    fileRequest.Method = WebRequestMethods.Ftp.DownloadFile;
    fileRequest.Credentials = new NetworkCredential(ftpUserName, ftpPassword);
    FtpWebResponse fileResponse = (FtpWebResponse)fileRequest.GetResponse();
    Stream fileStream = fileResponse.GetResponseStream();
    CloudBlockBlob blockBlob = container.GetBlockBlobReference(filename);

    await blockBlob.UploadFromStreamAsync(fileStream);
    log.LogInformation($"C# Timer trigger function executed at: {DateTime.Now}");
}

Answer 3

You cannot directly move the files from the FTP to Blob using the SDK. You have to download the files temporarily first - either into a stream (depending how large they become) or to a temp file.

However, if all you want to do is to move files from FTP to Blob on a schedule, I would actually look into using Azure Data Factory which is built exactly for tasks like that: https://docs.microsoft.com/en-us/azure/data-factory/connector-ftp