future

What's the difference between Future(blocking(blockingCall())) and blocking(Future(blockingCall())) ? Both of these are defined in scala.concurrent._ I've looked at the scala docs and some other stack overflow answers but remain unclear on what the difference is. Michael Zajac blocking acts as a hint to the ExecutionContext that it contains blocking code, so that it may spawn a new thread to prevent deadlocks. This presumes the ExecutionContext can do that, but not all are made to. Let's look at each one-by-one. Future(blocking(blockingCall())) This requires an implicit ExecutionContext to

Let's assume we have the following code: List<Future<?>> runningTasks; ExecutorService executor; ... void executeTask(Runnable task){ runningTasks.add(executor.submit(task)); } My questions are: Does runningTasks hold a reference to the task object? How long does it hold it for? Does it still hold it after the task is complete? In order to avoid memory leaks do I have to take care to remove the future that was added to the list? Until when the executor or the Future object holds a reference to it is an implementation detail . Therefore, if your tasks use a lot of memory such that you have to

What are futures? It's something to do with lazy evaluation. Motti There is a Wikipedia article about futures. In short, it's a way to use a value that is not yet known. The value can then be calculated on demand (lazy evaluation) and, optionally, concurrently with the main calculation. C++ example follows. Say you want to calculate the sum of two numbers. You can either have the typical eager implementation: int add(int i, int j) { return i + j; } // first calculate both Nth_prime results then pass them to add int sum = add(Nth_prime(4), Nth_prime(2)); or you can use the futures way using C+

I sometimes find myself in a situation where I have some Stream[X] , and a function X => Future Y , that I'd like to combine to a Future[Stream[Y]] , and I can't seem to find a way to do it. For example, I have val x = (1 until 10).toStream def toFutureString(value : Integer) = Future(value toString) val result : Future[Stream[String]] = ??? I tried val result = Future.Traverse(x, toFutureString) which gives the correct result, but seems to consume the entire stream before returning the Future, which more or less defeats the purpse I tried val result = x.flatMap(toFutureString) but that doesn

The new Future in Scala 2.10 uses an execution context for every operation where an action is called asynchronously (including map , filter , etc). Does this mean that every action will always be called individually through the execution context, or is it possible that this step is optimized away when chaining multiple transformations/filters each using the same execution context? I.e. if doing f.map(...).filter(...).map(...) , all with the same execution context, will this call execute() once (because it's clever enough to compose a synchronous function from the above), or three times? If the

Python web框架 Tornado异步非阻塞 异步非阻塞 阻塞式：(适用于所有框架，Django,Flask,Tornado,Bottle) 　　一个请求到来未处理完成，后续一直等待 　　解决方案：多线程，多进程 异步非阻塞(存在IO请求)： Tornado(单进程+单线程) 　　使用异步非阻塞，需要遵循Tornado框架内部规则，gen 　　多个连接请求，连接给服务端，如果是有异步非阻塞的话，服务端会接收所有的请求交由后台处理，等待其他链接的同时，原先连接不断开，直至返回后台处理完成的结果！ 　　外部请求，连接服务端 或在select中创建Future对象，然后服务端再把请求交给业务处理平台，此时select监听的列表中又会生成一个socket对象,当业务平台对请求处理完成之后就会把信息返回到服务端的select监听列表中，同时对这个Future对象赋值，用于标记服务端是否要给客户端返回请求信息。 　　执行流程，本质上都是返回一个future对象，如果对这个对象被set_result了就返回值，否则就是夯住，一直保持连接，不终止请求。 1、基本使用 装饰器 + Future 从而实现Tornado的异步非阻塞 class AsyncHandler(tornado.web.RequestHandler): @gen .coroutine def get( self ):

What is the best way to construct a completed future in Java? I have implemented my own CompletedFuture below, but was hoping something like this that already exists. public class CompletedFuture<T> implements Future<T> { private final T result; public CompletedFuture(final T result) { this.result = result; } @Override public boolean cancel(final boolean b) { return false; } @Override public boolean isCancelled() { return false; } @Override public boolean isDone() { return true; } @Override public T get() throws InterruptedException, ExecutionException { return this.result; } @Override public