Radicade/ServerTests/CdnRangeRequestTests.cs

using System;
using System.IO;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using RadicadeServer.CDN;
using RadicadeServer.DB;
using Xunit;

namespace RadicadeServer.Tests;

/// <summary>
/// The client's Unity asset bundle download is resumable: its string table carries
/// "bytes={0}-", "bytes={0}-{1}", "Accept-Ranges" and "Content-Range", so it asks the CDN for
/// byte ranges rather than a whole file. Every route that serves those bytes must therefore
/// process ranges — a range answer that returns the entire body makes the client re-transfer
/// the whole file once per range, which is how a 73 MB Studio bundle came to spend 228 s in
/// AssetBundle_Download, outlive the room's Photon connection, and fail the load with
/// code 6706-3. Dropping <c>enableRangeProcessing</c> is invisible at runtime (the download
/// still completes, just ~20x slower and past the network timeout), so it is pinned here.
/// </summary>
[Collection(DbFactoryCollection.Name)]
public class CdnRangeRequestTests : IDisposable
{
    private const string BlobName = "recdump-0cfd85d85c7b905dfbb83a6f3d3c887b.room";

    private readonly string root = Directory.CreateTempSubdirectory("radicade-cdn-range-test-").FullName;
    private readonly string? previousStorage;

    public CdnRangeRequestTests()
    {
        previousStorage = DBConfig.CDNStorage;
        DBConfig.CDNStorage = root;
        File.WriteAllText(Path.Join(root, BlobName), "blob");
    }

    public void Dispose()
    {
        DBConfig.CDNStorage = previousStorage!;

        try
        {
            Directory.Delete(root, true);
        }
        catch (IOException)
        {
        }
    }

    private static readonly string ImmutableCache = "public, max-age=31536000, immutable";
    private static readonly string ReplaceableCache = "public, max-age=86400";

    private const string BundleName = "0f0f0f0f-0f0f-0f0f-0f0f-0f0f0f0f0f0f.assetbundle";

    private static T WithHttpContext<T>(T controller) where T : Controller
    {
        controller.ControllerContext = new ControllerContext { HttpContext = new DefaultHttpContext() };
        return controller;
    }

    private static PhysicalFileResult RangeServed(IActionResult result)
    {
        var file = Assert.IsType<PhysicalFileResult>(result);
        Assert.True(file.EnableRangeProcessing, $"{file.FileName} is served without range processing");
        Assert.Equal("application/octet-stream", file.ContentType);
        return file;
    }

    [Fact]
    public void TheDataRouteThatCarriesAssetBundlesProcessesRanges()
    {
        // /data/{blob} is where the bundle bytes land: /rooms/unity_assets/... hands the
        // client a Filename and nothing else, so this is the URL the downloader ranges over.
        var file = RangeServed(new DataCDN().GetDataBlob(BlobName));

        Assert.Equal(Path.Join(root, BlobName), file.FileName);
    }

    [Fact]
    public void TheRoomAndUnityAssetRoutesProcessRanges()
    {
        RangeServed(new RoomsCDN().GetDataBlob(BlobName));
        RangeServed(new RoomsCDN().GetUnityAssetRaw(BlobName, 0, 1));
        RangeServed(new RoomsCDN().GetUnityAssetRaw(BlobName, null, null));
    }

    [Fact]
    public void TheInventionRouteProcessesRanges()
    {
        RangeServed(new InventionCDN().GetDataBlob(BlobName));
    }

    [Fact]
    public void TheBlobRoutesTellClientsTheyMayCacheWhatTheyDownloaded()
    {
        // A Studio room's bundle is the payload that decides whether the room loads at all.
        // With no cache directive the client's HTTP stack is free to fetch all of it again
        // on the next join, at ~100 ms RTT, and the room load is exactly as slow as it was
        // the first time.
        File.WriteAllText(Path.Join(root, BundleName), "bundle");

        var data = WithHttpContext(new DataCDN());
        data.GetDataBlob(BundleName);
        Assert.Equal(ImmutableCache, data.Response.Headers["Cache-Control"].ToString());

        var rooms = WithHttpContext(new RoomsCDN());
        rooms.GetUnityAssetRaw(BundleName, 0, 1);
        Assert.Equal(ImmutableCache, rooms.Response.Headers["Cache-Control"].ToString());

        // Room saves are content-addressed too, but admin repairs replace one under its
        // existing name, so they must expire rather than be pinned forever.
        data = WithHttpContext(new DataCDN());
        data.GetDataBlob(BlobName);
        Assert.Equal(ReplaceableCache, data.Response.Headers["Cache-Control"].ToString());

        rooms = WithHttpContext(new RoomsCDN());
        rooms.GetDataBlob(BlobName);
        Assert.Equal(ReplaceableCache, rooms.Response.Headers["Cache-Control"].ToString());
    }

    [Fact]
    public void AnUnknownBlobStillAnswersNotFound()
    {
        // Range support must not turn a missing file into a body, the way an unhandled
        // unsatisfiable range can.
        Assert.IsType<NotFoundResult>(new DataCDN().GetDataBlob("not-on-disk.room"));
        Assert.IsType<NotFoundResult>(new RoomsCDN().GetDataBlob("not-on-disk.room"));
        Assert.IsType<NotFoundResult>(new RoomsCDN().GetUnityAssetRaw("not-on-disk.room", 0, 1));
        Assert.IsType<NotFoundResult>(new InventionCDN().GetDataBlob("not-on-disk.room"));
    }
}