Azure Web Role "warm up" strategies

Question

I found that making requests to our web role after periods on inactivity would result in a very slow request (up to 30 seconds). After that initial request, the role would perform as it should.

After much Googling, I came across four different strategies (listed below):

(a) Disabling IIS idle timeout in RoleEntryPoint.OnStart()

public override bool OnStart()
{
    using (var server = new ServerManager())
    {
        server.ApplicationPoolDefaults.ProcessModel.IdleTimeout = TimeSpan.Zero;
        server.CommitChanges();
    }

    return base.OnStart();
}

This also requires that the role runs at an elevated level.

(b) Perform regular requests in the RoleEntryPoint.Run()

public override void Run()
{
    var localuri = new Uri(string.Format("https://{0}/Help", RoleEnvironment.CurrentRoleInstance.InstanceEndpoints["HttpsIn"].IPEndpoint));

    while (true)
    {
        try
        {
            var request = (HttpWebRequest)WebRequest.Create(localuri);
            request.Method = "GET";
            var response = request.GetResponse();
        }
        catch { }
        System.Threading.Thread.Sleep(3000);
    }
}

(c) Set preloadEnabled and startMode in the RoleEntryPoint.OnStart()

public override void OnStart()
{
    using (var serverManager = new ServerManager())
    {
        foreach (var application in serverManager.Sites.SelectMany(x => x.Applications))
        {
            application["preloadEnabled"] = true;
        }

        foreach (var applicationPool in serverManager.ApplicationPools)
        {
            applicationPool["startMode"] = "AlwaysRunning";
        }

        serverManager.CommitChanges();
    }

    return base.OnStart();
}

(d) And lastly, using Azure's "Always On" (EDIT: This is only for Azure websites unfortunately!)

Which of these strategies should I perform?

Answer 1

We use a combination of a couple of those answers and it works perfectly well for us, they're very quick to change and test however, it seems to cover all bases.

public override bool OnStart()
{
    ServicePointManager.DefaultConnectionLimit = 12;
    if(!RoleEnvironment.IsEmulated)
    {
        using(ServerManager serverManager = new ServerManager())
        {
            foreach (var app in serverManager.Sites.SelectMany(x => x.Applications))
            {
                app["preloadEnabled"] = true;
            }
            foreach (var appPool in serverManager.ApplicationPools)
            {
                    appPool.AutoStart = true;
                    appPool["startMode"] = "AlwaysRunning";
                    appPool.ProcessModel.IdleTimeout = TimeSpan.Zero;
                    appPool.Recycling.PeriodicRestart.Time = TimeSpan.Zero;
            }
            serverManager.CommitChanges();
        }
    }
    return base.OnStart();
}