synchronization

问题 I'm trying to delay specific threads inside a loop and I am not getting the behavior I want. I would like 1B to run only once 1A has been completed, while 2A runs in parallel on a separate thread. My implementation runs 1A then 1B then 2A instead. Any idea how I can fix this? Implementation override func viewDidLoad() { super.viewDidLoad() // 1 DispatchQueue.main.async { self.loopManager(printable: "1A") // 1A self.loopManager(printable: "1B") // 1B } // 2 DispatchQueue.main.async { self

问题 I am trying to create some tables using mysqldb. The issue is that when executing the python script db.py mysql throws the error: _mysql_exceptions.ProgrammingError: (2014, "Commands out of sync; you can't run this command now") db.py: import MySQLdb import MySQLdb.cursors def init_db(): db_conn = get_db_conn() cursor = db_conn.cursor() with open("tables.sql", 'r') as f: cursor.execute(f.read()) def get_db_conn(): return MySQLdb.connect( host="localhost", user="root", passwd="secretcat", db=

问题 I have a Java application in which I maintain set of IPs of my other servers in a hash map in memory. The hash map contains mapping between servers instance ids to servers ip address. I also maintain these servers information in a database for persistence. I am trying to solve a simple problem where I just need to cache the servers information in memory for faster access. So I have used hashmap for that. And I need to make sure that the server information in memory are NOT stale and all the

问题 If we have 2 classes that operate on the same object under different threads and we want to avoid race conditions, we'll have to use synchronized blocks with the same monitor like in the example below: class A { private DataObject mData; // will be used as monitor // thread 3 public setObject(DataObject object) { mData = object; } // thread 1 void operateOnData() { synchronized(mData) { mData.doSomething(); ..... mData.doSomethingElse(); } } } class B { private DataObject mData; // will be

问题 I need to build an application that does these things (in order): on load: 01- connect to MongoDB 'db' 02- creates a collection 'cas' 03- check if a web page has updates, if yes go to step 04, if not go to step 07 04- do web scraping (using Cheerio) of the web site and get a $ variable like that $ = cheerio.load(body); 05- elaborate this object to get only informations I'm interested in and organize them in a jsons object like this one: var jsons = [ {year: 2015, country: Germany, value: 51},

问题 I am creating a multiple threads and calling yield() inside it. The java.lang.Thread.yield() method causes the currently executing thread object to temporarily pause and allow other threads to execute. Will It be possible for other threads to execute which also want to go inside synchronized block? synchronized(this.lock) { //calling yield here. } thanks. 回答1: As far as I know, Yield() only gives up the remaining time slice on the CPU and steps back in the queue. It doesn't release any

问题 One could simply encapsulate number of synchronous requests as an asynchronous request. The "func" parameter within the below code could for example contain multiple synchronous requests in order. This should give you more power over data contrasting the use of the DOM as a medium to act on the data. (Is there another way?, it has been a while since I used javaScript) function asyncModule(func) { "use strict"; var t, args; t = func.timeout === undefined ? 1 : func.timeout; args = Array

问题 One could simply encapsulate number of synchronous requests as an asynchronous request. The "func" parameter within the below code could for example contain multiple synchronous requests in order. This should give you more power over data contrasting the use of the DOM as a medium to act on the data. (Is there another way?, it has been a while since I used javaScript) function asyncModule(func) { "use strict"; var t, args; t = func.timeout === undefined ? 1 : func.timeout; args = Array

问题 I have a HashMap that we use in our application. The data is populated from database during application initial load and then it's always just read and never updated. There will be multiple threads constantly reading the data. Since the data is never updated, we currently don't use any synchronization and is using just the HashMap. The way we define this now is: private volatile Map<Integer, MyData> myMap = new HashMap<>(); Now we want to update this data in map once a day by re-populating

问题 I have multiple projects with directory structure like this: /application/ /images/ /js/ /css/ /system/ index.php .htaccess Project specific files are in application folder, and "engine" stuff is in others (system/, css/, index.php, ..) . Now i'd like to sync my system files, which are the same to all projects, but still will be edited. So how to sync images, js, css, system, index.php, .htaccess between multiple projects with GIT? I'm new to git, but my first thought is to make master(empty)