Realm.LFS

Realm LFS (large file storage) is an extension of the Realm.NET SDK that exposes an abstraction for interacting with binary files that are transparently uploaded to a 3rd party service (e.g. S3/Azure Blob Storage) and their URL is subsequently updated in the Realm object for other clients to consume.

Installation

The Realm.LFS package is available on NuGet. To install it, run the following command in the Package Manager Console:

dotnet add package Realm.LFS

It provides the basic building blocks for working with binary data. In addition to it, there are 3 packages that provide an implementation for the RemoteStorageManager:

1. Realm.LFS.Functions provides a file manager that calls an Atlas Function to obtain a pre-signed url. Then it uploads data to the retried url.
2. Realm.LFS.S3 uses the S3 SDK to upload files to an S3 bucket.
3. Realm.LFS.Azure uses the Azure SDK to upload files to Azure Blob Storage.

If you use another service or have your own web server that can process the file uploads, you need to supply your own implementation of RemoteStorageManager.

Usage

For the most part, just replace byte[] properties with FileData ones:

public class Recipe : RealmObject
{
    public string Name { get; set; }

    public string Summary { get; set; }

    public IList<Ingredient> Ingredients { get; set; }

    // Replace this
    public byte[] Photo { get; set; }

    // with this
    public FileData Photo { get; set; }
}

To initialize the SDK, the minimum configuration you need to do is to configure the remote manager factory:

LFSManager.Initialize(new LFSOptions
{
    RemoteManagerFactory = (config) => new AtlasFunctionsStorageManager(config, "MyDataFunction")
});

The FileData class can be constructed from a Stream - if you already have a byte[], that can be used to create a MemoryStream.

When displaying an image from a FileData, the code should look something like:

public void PopulateImage(Recipe recipe)
{
    switch (recipe.Photo.Status)
    {
        case DataStatus.Local:
            var imagePath = recipe.Photo.LocalUrl;
            if (File.Exists(imagePath))
            {
                // we are the device that created the image - display it from disk
                MyImage.ImageSource = new FileImageSource(imagePath);
            }
            else
            {
                // this image was created on another device, but it hasn't uploaded it yet
                // to S3. Display a placeholder until the status changes to Remote
                MyImage.ImageSource = placeHolderImage;
            }
            break;
        case DataStatus.Remote:
            MyImage.ImageSource = new ImageSource(recipe.Photo.Url);
            break;
    }
}

FAQ

• Is this library stable?
  • The functionality is stable, but the API is still very much in flux. We will be adding more features and improving the API as we go. In it's current state it is likely to cover some straightforward use cases, but you should expect to run into limitations and missing functionality.
• Will you be actively maintaining this library?
  • This is a proof of concept project and we will not be actively developing it. We will be happy to add features and fix bugs as they are reported, but we won't be adding new functionality on a regular cadence.
• I need a feature, can I contribute?
  • Absolutely! The library is open source and as long as the feature is well thought out and fits with the overall design of the library we will be happy to accept contributions.