Jeff and .NET

The .NET musings of Jeff Putz

Sponsors

News

My Sites

Archives

September 2012 - Posts

.NET development on Macs

I posted the “exciting” conclusion of my laptop trade-ins and issues on my personal blog. The links, in chronological order, are posted below. While those posts have all of the details about performance and software used, I wanted to comment on why I like using Macs in the first place.

It started in 2006 when Apple released the first Intel-based Mac. As someone with a professional video past, I had been using Macs on and off since college (1995 graduate), so I was never terribly religious about any particular platform. I’m still not, but until recently, it was staggering how crappy PC’s were. They were all plastic, disposable, commodity crap. I could never justify buying a PowerBook because I was a Microsoft stack guy. When Apple went Intel, they removed that barrier. They also didn’t screw around with selling to the low end (though the plastic MacBooks bordered on that), so even the base machines were pretty well equipped. Every Mac I’ve had, I’ve used for three years. Other than that first one, I’ve also sold each one, for quite a bit of money.

Things have changed quite a bit, mostly within the last year. I’m actually relieved, because Apple needs competition at the high end. Other manufacturers are finally understanding the importance of industrial design. For me, I’ll stick with Macs for now, because I’m invested in OS X apps like Aperture and the Mac versions of Adobe products. As a Microsoft developer, it doesn’t even matter though… with Parallels, I Cmd-Tab and I’m in Windows.

So after three and a half years with a wonderful 17” MBP and upgraded SSD, it was time to get something lighter and smaller (traveling light is critical with a toddler), and I eventually ended up with a 13” MacBook Air, with the i7 and 8 gig upgrades, and I love it. At home I “dock” it to a Thunderbolt Display.

From HttpRuntime.Cache to Windows Azure Caching (Preview)

I don’t know about you, but the announcement of Windows Azure Caching (Preview) (yes, the parentheses are apparently part of the interim name) made me a lot more excited about using Azure. Why? Because one of the great performance tricks of any Web app is to cache frequently used data in memory, so it doesn’t have to hit the database, a service, or whatever.

When you run your Web app on one box, HttpRuntime.Cache is a sweet and stupid-simple solution. Somewhere in the data fetching pieces of your app, you can see if an object is available in cache, and return that instead of hitting the data store. I did this quite a bit in POP Forums, and it dramatically cuts down on the database chatter. The problem is that it falls apart if you run the app on many servers, in a Web farm, where one server may initiate a change to that data, and the others will have no knowledge of the change, making it stale. Of course, if you have the infrastructure to do so, you can use something like memcached or AppFabric to do a distributed cache, and achieve the caching flavor you desire.

You could do the same thing in Azure before, but it would cost more because you’d need to pay for another role or VM or something to host the cache. Now, you can use a portion of the memory from each instance of a Web role to act as that cache, with no additional cost. That’s huge. So if you’re using a percentage of memory that comes out to 100 MB, and you have three instances running, that’s 300 MB available for caching. For the uninitiated, a Web role in Azure is essentially a VM that runs a Web app (worker roles are the same idea, only without the IIS part). You can spin up many instances of the role, and traffic is load balanced to the various instances. It’s like adding or removing servers to a Web farm all willy-nilly and at your discretion, and it’s what the cloud is all about. I’d say it’s my favorite thing about Windows Azure.

The slightly annoying thing about developing for a Web role in Azure is that the local emulator that’s launched by Visual Studio is a little on the slow side. If you’re used to using the built-in Web server, you’re used to building and then alt-tabbing to your browser and refreshing a page. If you’re just changing an MVC view, you’re not even doing the building part. Spinning up the simulated Azure environment is too slow for this, but ideally you want to code your app to use this fantastic distributed cache mechanism.

So first off, here’s the link to the page showing how to code using the caching feature. If you’re used to using HttpRuntime.Cache, this should be pretty familiar to you. Let’s say that you want to use the Azure cache preview when you’re running in Azure, but HttpRuntime.Cache if you’re running local, or in a regular IIS server environment. Through the magic of dependency injection, we can get there pretty quickly.

First, design an interface to handle the cache insertion, fetching and removal. Mine looks like this:

public interface ICacheProvider
{
    void Add(string key, object item, int duration);
    T Get<T>(string key) where T : class;
    void Remove(string key);
}

Now we’ll create two implementations of this interface… one for Azure cache, one for HttpRuntime:

public class AzureCacheProvider : ICacheProvider
{
    public AzureCacheProvider()
    {
        _cache = new DataCache("default"); // in Microsoft.ApplicationServer.Caching, see how-to 
    }
   
    private readonly DataCache _cache;
    public void Add(string key, object item, int duration)
    {
        _cache.Add(key, item, new TimeSpan(0, 0, 0, 0, duration));
    }
   
public T Get<T>(string key) where T : class
    {
        return _cache.Get(key) as T;
    }
    public void Remove(string key)
    {
        _cache.Remove(key);
    }
}

public class LocalCacheProvider : ICacheProvider
{
    public LocalCacheProvider()
    {
        _cache = HttpRuntime.Cache;
    }
    private readonly System.Web.Caching.Cache _cache;
    public void Add(string key, object item, int duration)
    {
        _cache.Insert(key, item, null, DateTime.UtcNow.AddMilliseconds(duration), System.Web.Caching.Cache.NoSlidingExpiration);
    }
    public T Get<T>(string key) where T : class
    {
        return _cache[key] as T;
    }
    public void Remove(string key)
    {
        _cache.Remove(key);
    }
}

Feel free to expand these to use whatever cache features you want.

I’m not going to go over dependency injection here, but I assume that if you’re using ASP.NET MVC, you’re using it. Somewhere in your app, you set up the DI container that resolves interfaces to concrete implementations (Ninject call is a “kernel” instead of a container). For this example, I’ll show you how StructureMap does it. It uses a convention based scheme, where if you need to get an instance of IFoo, it looks for a class named Foo. You can also do this mapping explicitly. The initialization of the container looks something like this:

ObjectFactory.Initialize(x =>
            {
                x.Scan(scan =>
                        {
                            scan.AssembliesFromApplicationBaseDirectory();
                            scan.WithDefaultConventions();
                        });
                if (Microsoft.WindowsAzure.ServiceRuntime.RoleEnvironment.IsAvailable)
                    x.For<ICacheProvider>().Use<AzureCacheProvider>();
                else
                    x.For<ICacheProvider>().Use<LocalCacheProvider>();
            });

If you use Ninject or Windsor or something else, that’s OK. Conceptually they’re all about the same. The important part is the conditional statement that checks to see if the app is running in Azure. If it is, it maps ICacheProvider to AzureCacheProvider, otherwise it maps to LocalCacheProvider.

Now when a request comes into your MVC app, and the chain of dependency resolution occurs, you can see to it that the right caching code is called. A typical design may have a call stack that goes: Controller –> BusinessLogicClass –> Repository. Let’s say your repository class looks like this:

public class MyRepo : IMyRepo
{
    public MyRepo(ICacheProvider cacheProvider)
    {
        _context = new MyDataContext();
        _cache = cacheProvider;
    }

    private readonly MyDataContext _context;
    private readonly ICacheProvider _cache;

    public SomeType Get(int someTypeID)
    {
        var key = "somename-" + someTypeID;
        var cachedObject = _cache.Get<SomeType>(key);
        if (cachedObject != null)
        {
            _context.SomeTypes.Attach(cachedObject);
            return cachedObject;
        }
        var someType = _context.SomeTypes.SingleOrDefault(p => p.SomeTypeID == someTypeID);
        _cache.Add(key, someType, 60000);
        return someType;
    }
... // more stuff to update, delete or whatever, being sure to remove
// from cache when you do so
 

When the DI container gets an instance of the repo, it passes an instance of ICacheProvider to the constructor, which in this case will be whatever implementation was specified when the container was initialized. The Get method first tries to hit the cache, and of course doesn’t care what the underlying implementation is, Azure, HttpRuntime, or otherwise. If it finds the object, it returns it right then. If not, it hits the database (this example is using Entity Framework), and inserts the object into the cache before returning it.

The important thing not pictured here is that other methods in the repo class will construct the key for the cached object, in this case “somename-“ plus the ID of the object, and then remove it from cache, in any method that alters or deletes the object. That way, no matter what instance of the role is processing the request, it won’t find the object if it has been made stale, that is, updated or outright deleted, forcing it to attempt to hit the database.

So is this good technique? Well, sort of. It depends on how you use it, and what your testing looks like around it. Because of differences in behavior and execution of the two caching providers, for example, you could see some strange errors. For example, I immediately got an error indicating there was no parameterless constructor for an MVC controller, because the DI resolver failed to create instances for the dependencies it had. In reality, the NuGet packaged DI resolver for StructureMap was eating an exception thrown by the Azure components that said my configuration, outlined in that how-to article, was wrong. That error wouldn’t occur when using the HttpRuntime.

That’s something a lot of people debate about using different components like that, and how you configure them. I kinda hate XML config files, and like the idea of the code-based approach above, but you should be darn sure that your unit and integration testing can account for the differences.

Software development is (mostly) a trade, and what to do about it

(This is another cross-post from my personal blog. I don’t even remember when I first started to write it, but I feel like my opinion is well enough baked to share.)

I've been sitting on this for a long time, particularly as my opinion has changed dramatically over the last few years. That I've encountered more crappy code than maintainable, quality code in my career as a software developer only reinforces what I'm about to say.

Software development is just a trade for most, and not a huge academic endeavor.

For those of you with computer science degrees readying your pitchforks and collecting your algorithm interview questions, let me explain. This is not an assault on your way of life, and if you've been around, you know I'm right about the quality problem. You also know the HR problem is very real, or we wouldn't be paying top dollar for mediocre developers and importing people from all over the world to fill the jobs we can't fill.

I'm going to try and outline what I see as some of the problems, and hopefully offer my views on how to address them.

The recruiting problem

I think a lot of companies are doing it wrong. Over the years, I've had two kinds of interview experiences. The first, and right, kind of experience involves talking about real life achievements, followed by some variation on white boarding in pseudo-code, drafting some basic system architecture, or even sitting down at a comprooder and pecking out some basic code to tackle a real problem. I can honestly say that I've had a job offer for every interview like this, save for one, because the task was to debug something and they didn't like me asking where to look ("everyone else in the company died in a plane crash").

The other interview experience, the wrong one, involves the classic torture test designed to make the candidate feel stupid and do things they never have, and never will do in their job. First they will question you about obscure academic material you've never seen, or don't care to remember. Then they'll ask you to white board some ridiculous algorithm involving prime numbers or some kind of string manipulation no one would ever do. In fact, if you had to do something like this, you'd Google for a solution instead of waste time on a solved problem.

Some will tell you that the academic gauntlet interview is useful to see how people respond to pressure, how they engage in complex logic, etc. That might be true, unless of course you have someone who brushed up on the solutions to the silly puzzles, and they're playing you.

But here's the real reason why the second experience is wrong: You're evaluating for things that aren't the job. These might have been useful tactics when you had to hire people to write machine language or C++, but in a world dominated by managed code in C#, or Java, people aren't managing memory or trying to be smarter than the compilers. They're using well known design patterns and techniques to deliver software.

More to the point, these puzzle gauntlets don't evaluate things that really matter. They don't get into code design, issues of loose coupling and testability, knowledge of the basics around HTTP, or anything else that relates to building supportable and maintainable software. The first situation, involving real life problems, gives you an immediate idea of how the candidate will work out. One of my favorite experiences as an interviewee was with a guy who literally brought his work from that day and asked me how to deal with his problem. I had to demonstrate how I would design a class, make sure the unit testing coverage was solid, etc. I worked at that company for two years.

So stop looking for algorithm puzzle crunchers, because a guy who can crush a Fibonacci sequence might also be a guy who writes a class with 5,000 lines of untestable code. Fashion your interview process on ways to reveal a developer who can write supportable and maintainable code. I would even go so far as to let them use the Google. If they want to cut-and-paste code, pass on them, but if they're looking for context or straight class references, hire them, because they're going to be life-long learners.

The contractor problem

I doubt anyone has ever worked in a place where contractors weren't used. The use of contractors seems like an obvious way to control costs. You can hire someone for just as long as you need them and then let them go. You can even give them the work that no one else wants to do.

In practice, most places I've worked have retained and budgeted for the contractor year-round, meaning that the $90+ per hour they're paying (of which half goes to the person) would have been better spent on a full-time person with a $100k salary and benefits.

But it's not even the cost that is an issue. It's the quality of work delivered. The accountability of a contractor is totally transient. They only need to deliver for as long as you keep them around, and chances are they'll never again touch the code. There's no incentive for them to get things right, there's little incentive to understand your system or learn anything. At the risk of making an unfair generalization, craftsmanship doesn't matter to most contractors.

The education problem

I don't know what they teach in college CS courses. I've believed for most of my adult life that a college degree was an essential part of being successful. Of course I would hold that bias, since I did it, and have the paper to show for it in a box somewhere in the basement. My first clue that maybe this wasn't a fully qualified opinion comes from the fact that I double-majored in journalism and radio/TV, not computer science. Eventually I worked with people who skipped college entirely, many of them at Microsoft. Then I worked with people who had a masters degree who sucked at writing code, next to the high school diploma types that rock it every day. I still think there's a lot to be said for the social development of someone who has the on-campus experience, but for software developers, college might not matter.

As I mentioned before, most of us are not writing compilers, and we never will. It's actually surprising to find how many people are self-taught in the art of software development, and that should reveal some interesting truths about how we learn. The first truth is that we learn largely out of necessity. There's something that we want to achieve, so we do what I call just-in-time learning to meet those goals. We acquire knowledge when we need it.

So what about the gaps in our knowledge? That's where the most valuable education occurs, via our mentors. They're the people we work next to and the people who write blogs. They are critical to our professional development. They don't need to be an encyclopedia of jargon, but they understand the craft. Even at this stage of my career, I probably can't tell you what SOLID stands for, but you can bet that I practice the principles behind that acronym every day. That comes from experience, augmented by my peers. I'm hell bent on passing that experience to others.

Process issues

If you're a manager type and don't do much in the way of writing code these days (shame on you for not messing around at least), then your job is to isolate your tradespeople from nonsense, while bringing your business into the realm of modern software development. That doesn't mean you slap up a white board with sticky notes and start calling yourself agile, it means getting all of your stakeholders to understand that frequent delivery of quality software is the best way to deal with change and evolving expectations.

It also means that you have to play technical overlord to make sure the education and quality issues are dealt with. That's why I make the crack about sticky notes, because without the right technique being practiced among your code monkeys, you're just a guy with sticky notes. You're asking your business to accept frequent and iterative delivery, now make sure that the folks writing the code can handle the same thing. This means unit testing, the right instrumentation, integration tests, automated builds and deployments... all of the stuff that makes it easy to see when change breaks stuff.

The prognosis

I strongly believe that education is the most important part of what we do. I'm encouraged by things like The Starter League, and it's the kind of thing I'd love to see more of. I would go as far as to say I'd love to start something like this internally at an existing company.

Most of all though, I can't emphasize enough how important it is that we mentor each other and share our knowledge. If you have people on your staff who don't want to learn, fire them. Seriously, get rid of them. A few months working with someone really good, who understands the craftsmanship required to build supportable and maintainable code, will change that person forever and increase their value immeasurably.

More Posts