concurrency

Executor框架+实例

由 南笙酒味 提交于 2020-03-01 09:30:29
Executor框架 是指java 5中引入的一系列并发库中与executor相关的一些功能类，其中包括线程池，Executor，Executors，ExecutorService，CompletionService，Future，Callable等。 Executor框架简介 Executor框架描述 Executor框架 是指java 5中引入的一系列并发库中与executor相关的一些功能类，其中包括线程池，Executor，Executors，ExecutorService，CompletionService，Future，Callable等。 运用该框架能够很好的 将任务分成一个个的子任务 ，使并发编程变得方便。 Executor相关类图 该框架的类图（方法并没有都表示出来）如下： 创建线程池类别 创建线程池 Executors类，提供了一系列工厂方法用于创先线程池，返回的线程池都实现了ExecutorService接口。 public static ExecutorService newFixedThreadPool(int nThreads) 创建固定数目线程的线程池 public static ExecutorService newCachedThreadPool() 创建一个可缓存的线程池 创建一个可缓存的线程池，调用execute 将重用以前构造的线程

Swift3 concurrency

由 人走茶凉 提交于 2020-03-01 02:33:04
转自我的github: https://github.com/uniquejava/iOSConcurrencyDemo swift3 concurrency This repo is the steps breaking down from this excellent tutorial and an update for swift3 + xcode8. I seperated each step into its own commit, you can check the commit history for details. The major difference is on GCD part, for NSOperation part, the changes are minor. A compact example Example from here qos - new quality of service syntax weak self - to disrupt retain cycles async global background queue - for network query async main queue - for touching the UI. Of course you need to add some error checking to

Celery Beat: Limit to single task instance at a time

由 耗尽温柔 提交于 2020-02-26 18:23:05
问题 I have celery beat and celery (four workers) to do some processing steps in bulk. One of those tasks is roughly along the lines of, "for each X that hasn't had a Y created, create a Y." The task is run periodically at a semi-rapid rate (10sec). The task completes very quickly. There are other tasks going on as well. I've run into the issue multiple times in which the beat tasks apparently become backlogged, and so the same task (from different beat times) are executed simultaneously, causing

Celery Beat: Limit to single task instance at a time

由 有些话、适合烂在心里 提交于 2020-02-26 18:22:19
问题 I have celery beat and celery (four workers) to do some processing steps in bulk. One of those tasks is roughly along the lines of, "for each X that hasn't had a Y created, create a Y." The task is run periodically at a semi-rapid rate (10sec). The task completes very quickly. There are other tasks going on as well. I've run into the issue multiple times in which the beat tasks apparently become backlogged, and so the same task (from different beat times) are executed simultaneously, causing

Does SQL Server acquire locks even without an explicit transaction?

由 拟墨画扇 提交于 2020-02-24 09:22:11
问题 I was reading about MSSQL Locking for the first time, and it many places, the locking mechanism concepts depend on the existence of Transactions. I was wondering whether locking (in general) is possible without having any Transactions involved? 回答1: When no explicit transaction exists, each SQL statement is executed in an automatic (autocommit) transaction. Normal locking behavior will apply in that case and the locks released when the automatic transaction is completed as the statement

CompletableFuture supplyAsync

由 |▌冷眼眸甩不掉的悲伤 提交于 2020-02-17 07:04:39
问题 I've just started exploring some concurrency features of Java 8. One thing confused me a bit is these two static methods: CompletableFuture<Void> runAsync(Runnable runnable) CompletableFuture<U> supplyAsync(Supplier<U> supplier) Do anyone know why they choose to use interface Supplier? Isn't it more natural to use Callable, which is the analogy of Runnable that returns a value? Is that because Supplier doesn't throw an Exception that couldn't be handled? 回答1: Short answer No, it's not more

SQL Server deadlock when using PreparedStatements

由 房东的猫 提交于 2020-02-15 10:12:10
问题 I have a java servlet application and I'm using a prepared query to update a record in a SQL Server Database table. Lets say I want to execute UPDATE MyTable SET name = 'test' WHERE id = '10' . (Yes, id is a varchar) I used the following code to make this happen: PreparedStatement pstmt = con.prepareStatement("UPDATE MyTable SET name = ? WHERE id = ?"); pstmt.setString(1, getName() ); pstmt.setString(2, getID() ); pstmt.executeUpdate(); I found out that while I was running a JMeter script to

Java Socketing: My server class constantly takes in input but my client doesn't?

由 萝らか妹 提交于 2020-02-07 07:16:03
问题 Try to do some concurrent messaging between the server and the client. When they first connect to eachother and the Server sends the test string, the client gets it perfectly fine the first time. And the client can SEND messages just fine to the Server. But my Client class cant constantly check for messages like my Server can and idk what's wrong. Any suggestions? Server class code: import java.lang.*; import java.io.*; import java.net.*; import java.util.Random; import java.util.concurrent.*

Java Socketing: My server class constantly takes in input but my client doesn't?

由 给你一囗甜甜゛ 提交于 2020-02-07 07:14:07
问题 Try to do some concurrent messaging between the server and the client. When they first connect to eachother and the Server sends the test string, the client gets it perfectly fine the first time. And the client can SEND messages just fine to the Server. But my Client class cant constantly check for messages like my Server can and idk what's wrong. Any suggestions? Server class code: import java.lang.*; import java.io.*; import java.net.*; import java.util.Random; import java.util.concurrent.*

Condition instance signalAll() doesn't return

由 ♀尐吖头ヾ 提交于 2020-02-07 02:30:12
问题 I have the following code: @Log4j public class ItemStore { final Lock lock = new ReentrantLock(); final Condition hasItem = lock.newCondition(); private Map<String, String> store = new Hashtable<>(); public void put( String handle, String item) { store.put( handle, item ); log.info("stored " + handle ); hasItem.signalAll(); log.info("signaled all threads"); } public String fetchWithTimeout( String handle, long timeoutInSec ) throws InterruptedException { try { lock.lock(); while ( !store
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