Hot answers tagged async
14
It's certainly not new, it's just where the industry (not just MS) has been making a lot of progress lately in terms of making it more accessible to sub-geniuses.
Historically doing async programming was more cumbersome and difficult, consider the async socket api in windows for example.
With the new tools & abstractions coming out, it gets easier ...
11
So, something's been bugging me about the new async support in C# 5: The user presses a button which starts an async operation. The call returns immediately and the message pump starts running again - that's the whole point. So the user can press the button again - causing re-entrancy. What if this is a problem?
Let's start by noting that this is ...
10
Unfortunately, the answer is, "it depends." It would be easy for you to write a small program to empirically determine the times of both async and sync reads.
It will depend on lots of factors. Are they stored on spinning disks, SSD, or a network drive? What kind of CPU are you using? How many sockets/cores? Are you running in an VM or bare metal? Are ...
8
I think you're getting a few things confused, here. What you're asking for is already possible using System.Threading.Tasks, the async and await in C# 5 are just going to provide a little nicer syntactic sugar for the same feature.
Let's use a Winforms example - drop a button and a textbox on the form and use this code:
private void button1_Click(object ...
7
The only difference between the two is the synchronization used in StringBuffer. The overhead of synchronization is not huge in the grand scheme of things, but it is significant relative to the StringBuilder methods that don't have them. The JVM is doing work that it wouldn't otherwise have to do--especially with only one thread, etc.
If your code works ...
7
You will be able to accomplish your task using BackgroundWorker. It is a well known class, and many people have used it.
The new C# 5 async and await keywords basically just make it easier to write readable asynchronous code. There may be fewer tutorials and examples of how to accomplish various tasks with these keywords rather than BackgroundWorker.
...
6
is it OK to use blocking libs in non-blocking environment
No. A non-blocking server works because everything is non blocking. The moment you use any blocking code you create a huge bottle neck.
Non blocking servers use a single process/thread and an event loop. The moment you block inside the process your blocking the entire HTTP server.
This will ...
6
All of your logic is sound, except that I think your understanding of functional programming is a bit too extreme. In the real world functional programming, just like object-oriented, or imperative programming is about mindset and how you approach the problem. You can still write programs in the spirit of functional programming while modifying application ...
6
Async has 3 main advantages:
It lowers CPU utilization. This could be useful if you are also doing CPU-heavy operations with data you just read.
Using some kind of async infrastructure makes the code easy to paralelise. Especially if you are reading lots of files.
By sending multiple read-write requests to OS, OS and HW can re-order those operations to be ...
5
Why do you think disabling the button before the await and then re-enabling it when the call completes is fragile? Is it because you are worried that the button will never get re-enabled?
Well, if the call doesn't return then you can't make the call again, so it seems that this is the behaviour you want. This indicates an error state that you should be ...
5
I've used RequireJS on serious projects, and I love it, but it's not really meant to be an asynchronous loader. It's really meant to be a module system. Asynchronous loading is provided in service to that goal. It can be pushed to fill any of your requirements, but its loading services are designed to load modules, not arbitrary files.
Load JavaScript and ...
4
I don't know about "best practice". I do know the most common mistakes.
First Mistake: DOS Yourself
You use the webhandler to process the long running job. This can be bad or extremely bad depending on your percentage of hits that become long running jobs, how long they run and how much sustained traffic you get.
You want to make sure that you aren't ...
4
I'm not sure if this applies to you since I usually use WPF, but I see you referencing a ViewModel so it might.
Instead of disabling the button, set an IsLoading flag to true. Then any UI element you want to disable can be bound to the flag. The end result is that it becomes the UI's job to sort out it's own enabled state, not your Business Logic.
In ...
4
Yes, for the UI thread, the callback of a await operation will happen on the original thread of the caller.
Eric Lippert wrote an 8-part series all about it a year ago: Fabulous Adventures In Coding
EDIT: and here's Anders' //build/ presentation: channel9
BTW, did you notice that if you turn "//build/" upside down, you get "/plinq//" ;-)
4
It's highly unlikely that you can achieve with plain js the same level of conciseness and expressiveness in working with callbacks that C# 5 has. The compiler does the work in writing all that boilerplate for you, and until the js runtimes will do that, you will still have to pass an occasional callback here and there.
However, you may not always want to ...
3
In the demos I've seen, they disable the button before the await call
and enable it again afterwards. This seems to me like a very fragile
solution in a real-world app.
There is nothing fragile about this, and it is what the user would expect. If the user needs to wait before hitting the button again then make them wait.
I can see how certain ...
3
In short, yes.
Synchronous HTTP requests halt execution of subsequent code while they are en route. While browsers may no longer block the UI during this time, we're relying on the user's available bandwidth, network reliability, and the server's current load for the performance of our code. This is generally not good practice.
On the MDN "Using ...
3
You're planning to deal with much concurrent activity, so that means you've got to think in terms of atomic operations. That means using transactions.
Now, you don't want to hold a transaction for a long time as it blocks other transactions, so you have to think about using the transactions to protect minimal state changes and putting guards on the UPDATE ...
3
This is a fascinating question. The most interesting take on it is, in my view, the approach adopted in Clojure and explained in this video:
http://www.infoq.com/presentations/Value-Identity-State-Rich-Hickey
Basically the "solution" proposed is as follows:
You write most of your code as classic "pure" functions with immutable data structures and no side ...
3
The async and await keywords will not make your application more responsive on their own. They simply make the calling and handling of methods that return Task objects more convenient. In order to make async/await actually use background threads, you will need to combine with the usage of things like:
Task.Start() - Starts a given task using the ...
2
AJAX (Asynchronous JavaScript and XML) describes both of your bullet points. So it might have been better for the job description to say that outright. XSLT and XPath are just ways to use/structure/interact with the XML DOM.
When a C#.Net Developer-job is advertised saying, "the following skill is required as mentioned in 1 and 2", then what does it ...
2
Well, I can't speak to the job requirement that you're staring at, but we have a similar situation (at the job I'm leaving at the end of this month) that could probably be described much like your advert (although we use .NET 3.5, and use flash instead of silverlight). Without getting into too much details, many government forms are now electronically filed ...
2
One note: a functional language is pure, but its runtime is not.
For example, the Haskell runtimes involve queues, thread multiplexing, garbage collection, etc... all of which is not pure.
A good example is laziness. Haskell supports lazy evaluation (that is the default, actually). You create a lazy value by preparing an operation, you can then create ...
2
I'm confused as to how this "no side-effects" philsophy works with asynchronous programming. By asynchronous programming I mean ...
That would be the point, then.
A sound, no side-effect style is incompatible with frameworks that depend on state. Find a new framework.
Python's WSGI standard, for example, allows us to build no side-effect ...
2
Disabling the widget is the least complex and error-prone option. You disable it in the handler before starting the async operation and you re-enable it at the end of the operation. So the disable+enable for each control are kept local to handling of that control.
You can even create a wrapper, that will take a delegate and control (or more of them), ...
2
Which one of those libraries has Python 3 support? Most networking and web programming libraries have not yet been ported to Python 3. If you continue to have problems finding a library, I suggest switching down to Python 2.x . It seems from the benchmarks in the article that Tornado has the highest performance. Another option not listed in the article is ...
2
You do realize the first A of AJAX is Asynchronous, right? That is one source of it for the past decade. Multi-core CPUs may be another reason for some of this as more threads can be handled at once the problem of synchronization which has been around for a while, see Two Generals' Problem which had a proof written in 1975.
Asynchrony in C# 5.0 part ...
2
Maybe you could implement some sort of "auto-loading tree".
Start with the first node. This node fetches data from server. For each item found in the response, it creates a child node that will load the appropriate data. And so on...
One thing you need to know is "When is it complete ?"
This can be handled with events. Each node send an event up when all ...
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