nonblocking | 易学教程

python: nonblocking subprocess, check stdout

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问题 Ok so the problem I'm trying to solve is this: I need to run a program with some flags set, check on its progress and report back to a server. So I need my script to avoid blocking while the program executes, but I also need to be able to read the output. Unfortunately, I don't think any of the methods available from Popen will read the output without blocking. I tried the following, which is a bit hack-y (are we allowed to read and write to the same file from two different objects?) import

non-blocking IO vs async IO and implementation in Java

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Trying to summarize for myself the difference between these 2 concepts (because I'm really confused when I see people are using both of them in one sentence, like "non-blocking async IO" which I'm trying to figure out what does it mean). So, in my understanding non-blocking IO is primary the OS mechanism to process the IO if there is any data ready, otherwise just return error/do nothing. In async IO you just provide a callback, and your application will be notified when the data is available. So what is actually "non-blocking async IO"? And how all them can be implemented in Java (standard

What's the difference between: Asynchronous, Non-Blocking, Event-Base architectures?

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What's the difference between: Asynchronous , Non-Blocking , and Event-base architectures? Can something be both asynchronous and non-blocking (and event-based )? What's most important in programming, to have something: asynchronous, non-blocking and/or event-base (or all 3)? If you could provide examples, that would be great. This question is being asked because I was reading this great StackOverflow article on a similar topic but it doesn't answer my questions above. Asynchronous Asynchronous literally means not synchronous. Email is asynchronous. You send a mail, you don't expect to get a

What is the preferred way of performing non blocking I/O in Ruby?

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问题 If say I want to retrieve a web page for parsing, but not block the CPU while the I/O is taking place. Is there something equivalent to Python's Eventlet library? 回答1: The best HTTP client library for Ruby is Typhoeus, it can be used to perform multiple HTTP requests in parallel in a non-blocking fashion. There is a blocking and non-blocking interface: # blocking response = Typhoeus::Request.get("http://stackoverflow.com/") puts response.body # non-blocking request1 = Typhoeus::Request.new(

How to reset a socket back to blocking mode (after I set it to nonblocking mode)?

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I have read this regarding setting a socket to non-blocking mode. http://www.gnu.org/software/libc/manual/html_mono/libc.html#File-Status-Flags Here is what I did: static void setnonblocking(int sock) { int opts; opts = fcntl(sock,F_GETFL); if (opts < 0) { perror("fcntl(F_GETFL)"); exit(EXIT_FAILURE); } opts = (opts | O_NONBLOCK); if (fcntl(sock,F_SETFL,opts) < 0) { perror("fcntl(F_SETFL)"); exit(EXIT_FAILURE); } return; } How can I set the socket back to Blocking mode? I don't see a O_BLOCK flag? Thank you. Did you try clearing the O_NONBLOCK flag? opts = opts & (~O_NONBLOCK) Here is a more

Java serialization, ObjectInputStream.readObject(), check if will block

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I'm using an ObjectInputStream to call readObject for reading in serialized Objects . I would like to avoid having this method block, so I'm looking to use something like Inputstream.available() . InputStream.available() will tell you there are bytes available and that read() will not block. Is there an equivalent method for seriailzation that will tell you if there are Object s available and readObject will not block? No. Although you could use the ObjectInputStream in another thread and check to see whether that has an object available. Generally polling isn't a great idea, particularly with

How can I execute a node.js module as a child process of a node.js program?

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Here's my problem. I implemented a small script that does some heavy calculation, as a node.js module. So, if I type "node myModule.js", it calculates for a second, then returns a value. Now, I want to use that module from my main Node.JS program. I could just put all the calculation in a "doSomeCalculation" function then do: var myModule = require("./myModule"); myModule.doSomeCalculation(); But that would be blocking, thus it'd be bad. I'd like to use it in a non-blocking way, like DB calls natively are, for instance. So I tried to use child_process.spawn and exec, like this: var spawn =

using Flask and Tornado together?

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I am a big fan of Flask - in part because it is simple and in part because has a lot of extensions . However, Flask is meant to be used in a WSGI environment, and WSGI is not a non-blocking, so (I believe) it doesn't scale as well as Tornado for certain kinds of applications. Since each one has an URL dispatcher which will call a function, and both will use Python files (in Django you dont launch the python file but in flask or tornado you do) do does it make sense to have two seperate parts to your website - one part running the non-blocking jobs with Tornado, and the other part written with

Java thread per connection model vs NIO

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问题 Is the non-blocking Java NIO still slower than your standard thread per connection asynchronous socket? In addition, if you were to use threads per connection, would you just create new threads or would you use a very large thread pool? I'm writing an MMORPG server in Java that should be able to scale 10000 clients easily given powerful enough hardware, although the maximum amount of clients is 24000 (which I believe is impossible to reach for the thread per connection model because of a

How to use QThread correctly in pyqt with moveToThread()?

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i read this article How To Really, Truly Use QThreads; The Full Explanation , it says instead of subclass qthread, and reimplement run(), one should use moveToThread to push a QObject onto QThread instance using moveToThread(QThread*) here is the c++ example, but i don't know how to convert it to python code. class Worker : public QObject { Q_OBJECT QThread workerThread; public slots: void doWork(const QString &parameter) { // ... emit resultReady(result); } signals: void resultReady(const QString &result); }; class Controller : public QObject { Q_OBJECT QThread workerThread; public: