Asynchronous Programming - Easier Asynchronous Programming with the New Visual Studio Async CTP. Imagine what the world would be like if people worked the same way as computer programs: void ServeBreakfast(Customer diner){ var order = ObtainOrder(diner); var ingredients = ObtainIngredients(order); var recipe = ObtainRecipe(order); var meal = recipe.Prepare(ingredients); diner.Give(meal);} Each subroutine can, of course, be broken down further; preparing the meal might involve heating pans, cooking omelets and toasting bread.
Were humans to perform these sorts of tasks like typical computer programs, we’d carefully write down everything as sequences of hierarchical tasks in a checklist and obsessively ensure that each job was complete before embarking on the next. A subroutine-based approach seems reasonable—you can’t cook the eggs before you get the order—but in fact it both wastes time and makes the application appear unresponsive. Solution One: Hire More Staff by Making More Threads Making someone’s breakfast is a whimsical example, but the reality, of course, is anything but. Asynchronous Programming - Pause and Play with Await.
Asynchronous methods in the upcoming versions of Visual Basic and C# are a great way to get the callbacks out of your asynchronous programming. In this article, I’ll take a closer look at what the new await keyword actually does, starting at the conceptual level and working my way down to the iron. Sequential Composition Visual Basic and C# are imperative programming languages—and proud of it! This means they excel in letting you express your programming logic as a sequence of discrete steps, to be undertaken one after the other. Most statement-level language constructs are control structures that give you a variety of ways to specify the order in which the discrete steps of a given body of code are to be executed: Building up your logic using control structures results in sequential composition, and this is the lifeblood of imperative programming.
Continuous Execution This continuity is sometimes problematic. Here’s an example of a method that is seriously blocking: Asynchronous Methods. Async articles - Fabulous Adventures In Coding. A long time ago on this blog, someone pointed out that there are similarities between async methods and iterator blocks. In both cases the compiler transforms your single method into a class and a state machine, and in principle it appears that the async feature could be used to simulate a iterator method (or vice versa). However, the relationship between the two is fuzzy in my mind and could use some clarification.
However, what interests me most is the question of whether the async methods are in some way equivalent to Cω's stream flattening. Since C# iterators are not flattened, performance suffers when using them to enumerate any tree-like data structure or state space... I wrote about this at loyc-etc.blogspot.com/... /c-stream-flattening.html . So, if async methods provide flattening (and I think they do), in principle someone could use them to write an iterator that walks a tree (using code that is easy-to-write and O(1) per tree node). Eduasync part 5: making Task<T> awaitable - Jon Skeet: Coding Blog. In part 3 we looked at what the C# 5 compiler required for you to "await" something. The sample used a class which actually had an instance method called GetAwaiter, but I mentioned that it could also be an extension method.
In this post, we'll use that ability to make Task<T> awaitable - at which point we have everything we need to actually see some asynchronous behaviour. Just like the last part, the code here is pretty plain - but by the end of the post we'll have a full demonstration of asynchrony. I should make it clear that this isn't absolutely everything we'll want, but it's a good start. TaskAwaiter<T> As it happens, I'm using the same type name as the async CTP does for "something which can await a task" - TaskAwaiter.
All the task awaiter needs is a reference to the task that it's awaiting - it doesn't need to know anything about the async method which is waiting for it, for example. The extension method on Task<T> is trivial: publicstruct TaskAwaiter{ privatereadonly Task. Async Redis await BookSleeve. BookSleeve has now been succeeded by StackExchange.Redis, for lots of reasons. The API and intent is similar, but the changes are significant enough that we had to reboot. All further development will be in StackExchange.Redis, not BookSleeve. At Stack Exchange, performance is a feature we work hard at. Crazy hard. Whether that means sponsoring load-balancer features to reduce system impact, or trying to out-do the ORM folks on their own turf. One of the many tools in our performance toolkit is Redis; a highly performant key-value store that we use in various ways: as our second-level cache for various tracking etc counters, that we really don’t want to bother SQL Server about for our pub/sub channels for various other things that don’t need to go direct to SQL Server It is really fast; we were using the redis-sharp bindings and they served us well.
Enter BookSleeve Seriously, what now? And we’re giving it away (under the Apache License 2.0)! So; what are the goals? Where are we? BookSleeve.