MVC Split AB Test Controller

SplitABController.cs

using System;
using System.Web;
using System.Web.Mvc;

public abstract class SplitABController : Controller
{
    private static readonly Results results = new Results();
    private const string B_TEST_SUFFIX = "_B";
    private const string SPLIT_TEST_VIEW_COOKIE_NAME = "SPLIT_TEST_VIEW_COOKIE";
    private static ViewFilesCache cache;
    
    public static Results GetSplitTestResults() { return results; }
    
    protected over ride void OnActionExecuting(ActionExecutingContext filterContext)
    {
        AddSplitTestResultsToResultsMap(filterContext);
        base.OnActionExecuting(filterContext);
    }
    
    private void AddSplitTestResultsToResultsMap(ActionExecutingContext filterContext)
    {
        // If last request was not for a split test view then just return
        if (Request.Cookies[SPLIT_TEST_VIEW_COOKIE_NAME] == null) return;
        
        // Add this controller/action to the results of the split test
        ResultRow rr = ResultRow.FromString(Request.Cookies[SPLIT_TEST_VIEW_COOKIE_NAME].Value);
        results.RemoveOneFromResults(rr);
        rr.ToControllerName = filterContext.ActionDescriptor.ControllerDescriptor.ControllerName;
        rr.ToAction = filterContext.ActionDescriptor.ActionName;
        results.AddOneToResults(rr);
    }
    
    /// <summary>
    /// If the view has a _B counterpart then we mark this action as a 'Split Test' we
    /// then record the results of this split view in the next request (OnActionExecuting).
    ///
    /// This method also determines if we should supply the A or B view depending on the
    /// 'ShouldRequestUseBView' algorithm.
    /// </summary>
    protected override ViewResult View(string viewName, string masterName, object model)
    {
        if (String.IsNullOrEmpty(viewName)) { viewName = (string) RouteData.Values["action"]; }
        bool isSplitTestingView = IsSplitTestingView(masterName, viewName);
        // If this view does not have a _B counterpart then we mark this request as non split test (by
        // removing the 'SPLIT_TEST_VIEW_COOKIE_NAME' cookie) and just send control to base.View
        if (!isSplitTestingView)
        {
            Response.Cookies.Remove(SPLIT_TEST_VIEW_COOKIE_NAME);
            return base.View(viewName, masterName, model);
        }
        // Wether to use the A or B view depending on the 'ShouldRequestUseBView' algorithm
        bool useb = ShouldRequestUseBView();
        // Lets create a results row and store it in the cookie (SPLIT_TEST_VIEW_COOKIE_NAME). This will let the
        // next request (OnActionExecuting) know that we just hit a split test view.
        ResultRow rr = new ResultRow {FromController = this, FromAction = viewName, UsedBView = useb};
        Response.Cookies.Add(new HttpCookie(SPLIT_TEST_VIEW_COOKIE_NAME, rr.ToString()));
        results.AddOneToResults(rr);
        
        // Display the appropriate view (A or B)
        return useb
        ? base.View(viewName + B_TEST_SUFFIX, masterName, model)
        : base.View(viewName, masterName, model);
    }
    
    /// <summary>
    /// Returns wether the specified view has a _B counterpart.
    /// </summary>
    private bool IsSplitTestingView(string masterName, string viewName)
    {
        if (cache == null) { lock (GetType()) { if (cache == null) { cache = new ViewFilesCache(B_TEST_SUFFIX); } } }
        return cache.HasSplitTestingAlternative(this, masterName, viewName);
    }
    
    /// <summary>
    /// If odd IP then use 'B' view.  This will give a ~50% A / B split.
    /// </summary>
    private bool ShouldRequestUseBView()
    {
        return Int32.Parse(Request.UserHostAddress.Substring(Request.UserHostAddress.LastIndexOf('.') + 1)) % 2 == 1;
    }
}