event-loop | 易学教程

Should I use two asyncio event loops in one program?

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问题 I want use the Python 3 asyncio module to create a server application. I use a main event loop to listen to the network, and when new data is received it will do some compute and send the result to the client. Does 'do some compute' need a new event loop? or can it use the main event loop? 回答1: You can do the compute work in the main event loop, but the whole event loop will be blocked while that happens - no other requests can be served, and anything else you have running in the event loop

What is a browser event loop?

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问题 I have been doing some web application programming using GWT and have been confused by the term "browser event loop". I have encountered situations where I need to execute deferred commands and "do something" after the browser event loop completes. I would like to know as to what exactly it is and what happens during the event loop process and in which order? 回答1: A browser event loop is a thread started by the browser that is constantly scanning for and running different events, just like it

Qt event loop and unit testing?

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I'we started experimenting with unit testing in Qt and would like to hear comments on a scenario that involves unit testing signals and slots. Here is an example: The code i would like to test is (m_socket is a pointer to QTcpSocket ): void CommunicationProtocol::connectToCamera() { m_socket->connectToHost(m_cameraIp,m_port); } Since that is an asynchronous call i can't test a returned value. I would however like to test if the response signal that the socket emits on a successful connection ( void connected () ) is in fact emitted. I've written the test below: void CommunicationProtocolTest:

How to detect and measure event loop blocking in node.js?

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问题 I'd like to monitor how long each run of the event loop in node.js takes. However I'm uncertain about the best way to measure this. The best way I could come up with looks like this: var interval = 500; var interval = setInterval(function() { var last = Date.now(); setImmediate(function() { var delta = Date.now() - last; if (delta > blockDelta) { report("node.eventloop_blocked", delta); } }); }, interval); I basically infer the event loop run time by looking at the delay of a setInterval . I

Single threaded and Event Loop in Node.js

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问题 First of all, I am starter trying to understand what is Node.Js. I have two questions. First Question From the article of Felix, it said "there can only be one callback firing at the same time. Until that callback has finished executing, all other callbacks have to wait in line". Then, consider about the following code (copied from nodejs official website) var http = require('http'); http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello

How are the Event Loop, Callback Queue, and Javascript’s single thread connected?

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问题 GENERAL GOAL I’d like to know how the following pieces of a javascript environment interconnect as a system . Javascript Engine Event Loop Event Queue We can limit this to a browser environment since node has been covered in another article (here) THINGS I (believe to) UNDERSTAND: Javascript is single threaded and therefore only has one callstack. Javascript environments provide only a few functions that are truly asynchronous. These may include setTimeout(), setInterval(), and I/O function(s

node.js Event Loop Diagnostics

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问题 Is it possible to peek at the event loop for diagnostics? I would like to know how many events are currently waiting for execution (excluding setTimeout/interval). Update: I'd like to do this from inside the running node process. 回答1: Updated for nodejs 0.10 with setImmediate() While I wasn't able to find the number of waiting events in the queue I found another health metric that might be useful: var ts=Date.now(); setImmediate(function() { var delay=Date.now()-ts; }); delay will contain the

Python3 Asyncio call from Flask route

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问题 I want to execute an async function everytime the flask route is executed. Currently my abar function is never executed. Can you tell me why? Thank you very much: import asyncio from flask import Flask async def abar(a): print(a) loop = asyncio.get_event_loop() app = Flask(__name__) @app.route("/") def notify(): asyncio.ensure_future(abar("abar"), loop=loop) return "OK" if __name__ == "__main__": app.run(debug=False, use_reloader=False) loop.run_forever() I tried it also to put the one

what is mean by event loop in node.js ? javascript event loop or libuv event loop?

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In Node.js we a lot talk about the event loop, so I want to know which event loop we are talking about, the Javascript event loop or the libuv event loop ? I guess libuv event loop that provides abstraction for multiple operating system of multiplexing i/o ? Am I right? If not so please explain how this stuff works? I need some internal knowledge, I know what an event loop is, I just want to know how it is connected? Currently Node uses the the event loop provided by libuv - namely its default event loop: uv_default_loop() . See: An Introduction to libuv by Nikhil Marathe: A default loop is

Python Windows `msvcrt.getch()` only detects every 3rd keypress?

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My code is below: import msvcrt while True: if msvcrt.getch() == 'q': print "Q was pressed" elif msvcrt.getch() == 'x': sys.exit() else: print "Key Pressed:" + str(msvcrt.getch() This code is based on this question ; I was using it to acquaint myself with getch . I've noticed that it takes 3 pressing the key 3 times to output the text once. Why is this? I'm trying to use it as an event loop, and that's too much of a lag... Even if I type 3 different keys, it only outputs the 3rd keypress. How can I force it to go faster? Is there a better way to achieve what I'm trying to achieve? Thanks!