Photo Hosting Options

The default hosting implementation (EdFi.Dashboards.Resources.Images.ContentProvider.StudentFileSystemBasedImageContentProvider and related classes) serves up the images from the file system, and is supported by the FilePhotoStorage implementation. To enable this implementation, the configuration-specific installer needs to be modified to use these implementations in a chain instead of the static providers (see below):

protected override void RegisterIImageContentProvider(IWindsorContainer container)
{
    var assemblyTypes = typeof(Marker_EdFi_Dashboards_Resources).Assembly.GetTypes();

    var chainTypes = (from t in assemblyTypes
                        let serviceType = t.GetInterface(typeof(IImageContentProvider).Name)
                        where serviceType != null && !t.IsAbstract && t.Name.EndsWith("FileSystemBasedImageContentProvider")
                        select t);

    var chainRegistrar = new ChainOfResponsibilityRegistrar(container);
    chainRegistrar.RegisterChainOf<IImageContentProvider, NullImageProvider>(chainTypes.ToArray(), "ImageContentProviderChain");
}

For ease of developer use and initial setup, the default implementation serves up photo images from file system of the Dashboard UI web server. While this is suitable for small implementations, performance analysis shows that having a separate web server for hosting images provides the best performance. This separate web server should be routed to by a separate subdomain with its own SSL certificate.

The web server should be configured to serve default images for people and education organizations if the requested image is not found. This can be accomplished in IIS with the URL Rewrite Module 2.0 Alternately nginx can be used for a lightweight web server with retry rules.

The web server should request the browser cache the image for an extended period of time to reduce the number of requests handled by the server. The cache expiration should take into account student photos only being refreshed once a school year. It is further recommend to add a load balancer in front of the image hosting web server and installing the certificate there. This will facilitate adding additional web servers if needed. The production Ed-Fi Dashboard instance should be configured to use the RemoteImageLinkProvider for the IImageLinkProvider. This provider requires a ‘RemoteImagePath’ entry in the appSettings section of the web.config for the Ed-Fi Dashboard. The value of the setting should be the base url for image hosting. For example: ‘https://images.edfidashboard.org’.

General Architecture

The sections below outline some of the major code elements that support the import and saving of the photos. Each interface provides a simple extension point.

PhotoManagementController

Controller that receives the bytes of the uploaded file chunk by chunk and assembles them to create a single file for processing. This controller calls into the PhotoManagementService.

PhotoManagementService

Assembles a request object with the current district Id and selected school Id with the file bytes that represent the school. This service calls into the PhotoProcessor.

PhotoProcessor

The conductor that calls into all of the underlying implementations for specified processing. This calls into the IPackageReader, IIdentifierProvider, IPhotoResizer, and IPhotoStorage.

IPackageReader

Through a chain of responsibility, this represents multiple parsers that attempt to parse the uploaded file. If parsed successfully, a collection of OriginalPhoto instances are returned.

public abstract class OriginalPhoto
{
    public byte[] Photo { get; set; }

    /// <summary>
    /// Gets the uniquely identifying information about the photo.
    /// </summary>
    public abstract string FriendlyName { get; }
}

public class UniqueOriginalPhoto : OriginalPhoto
{
    public long Id { get; set; }
    public IdentifierType IdentifierType { get; set; }

    public override string FriendlyName
    {
        get { return string.Format("{0} - {1}", Id, IdentifierType); }
    }
}

IIdentifierProvider

Through another chain of responsibility, this represents multiple lookup providers that attempt to find the unique Ids for each entity that has a photo. If parsed successfully, an Identifier instance is returned.

public class Identifier
{
    public int Id { get; set; }
    public IdentifierType Type { get; set; }
}

public enum IdentifierType
{
    Student,
    Staff,
    School,
    District
}

IPhotoResizer

Resizes the original photo into 3 separate sizes - list, thumbnail, and profile (for the header).

IPhotoStorage

Stores each version of the photo.