[英]Issues with Implementing Multiple Consumer Multiple Producer in Java
我用一個阻塞隊列編寫了一個簡單的消費者 - 生產者問題,該隊列有多個生產者,多個消費者接受並將整數放在隊列中。 但是,當我嘗試測試它時,結果並不理想,例如隊列的大小不正確。 我不認為消費者和生產者規模正在同步。 此外,我對生產者和消費者都進行了2秒鍾的睡眠,但在測試時,每兩秒就會打印出2個生產者和2個消費者的結果。 有誰知道我做錯了什么? 也許我開始錯誤的線程? 我評論了另一種方式,但結果仍然是錯誤的。
結果:
run:
Producing 425 Thread-0 size left 0
Consuming 890 Thread-3 size left 0
Consuming 425 Thread-2 size left 0
Producing 890 Thread-1 size left 0
Consuming 192 Thread-2 size left 0
Consuming 155 Thread-3 size left 0
Producing 155 Thread-1 size left 0
Producing 192 Thread-0 size left 0
Consuming 141 Thread-2 size left 1
Producing 141 Thread-0 size left 0
Producing 919 Thread-1 size left 0
Consuming 919 Thread-3 size left 0
Producing 361 Thread-1 size left 0
Producing 518 Thread-0 size left 0
Consuming 518 Thread-3 size left 0
Consuming 361 Thread-2 size left 0
Producing 350 Thread-0 size left 1
Consuming 350 Thread-3 size left 0
Consuming 767 Thread-2 size left 0
Producing 767 Thread-1 size left 0
制片人
import java.util.Random;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Producer implements Runnable {
BlockingQueue<Integer> items = new LinkedBlockingQueue<>();
public Producer(BlockingQueue<Integer> q) {
this.items = q;
}
private int generateRandomNumber(int start, int end) {
Random rand = new Random();
int number = start + rand.nextInt(end - start + 1);
return number;
}
public void run() {
for (int i = 0; i < 5; i++) {
int rand = generateRandomNumber(100, 1000);
try {
items.put(rand);
System.out.println("Producing " + rand + " " + Thread.currentThread().getName() + " size left " + items.size());
Thread.sleep(3000);
} catch (InterruptedException ex) {
Logger.getLogger(ProducerConsumer.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
消費者
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Consumer implements Runnable {
BlockingQueue<Integer> items = new LinkedBlockingQueue<>();
public Consumer(BlockingQueue<Integer> q) {
this.items = q;
}
public void run() {
while (true) {
try {
System.out.println("Consuming " + items.take() + " " + Thread.currentThread().getName() + " size left " + items.size());
Thread.sleep(3000);
} catch (InterruptedException ex) {
Logger.getLogger(ProducerConsumer.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
測試
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
public class ProducerConsumer {
public static void main(String args[]) {
BlockingQueue<Integer> items = new LinkedBlockingQueue<>();
Producer producer = new Producer(items);
Consumer consumer = new Consumer(items);
Thread t1 = new Thread(producer);
Thread t2 = new Thread(producer);
Thread t3 = new Thread(consumer);
Thread t4 = new Thread(consumer);
/*
Thread t1 = new Thread(new Producer());
Thread t2 = new Thread(new Producer());
Thread t3 = new Thread(new Consumer());
Thread t4 = new Thread(new Consumer());
*/
t1.start();
t2.start();
t3.start();
t4.start();
}
}
更新:我試圖實現可重入鎖定,但我的程序在鎖定行停止。 有幫助嗎? 消費者
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class Consumer implements Runnable {
//private BlockingQueue<Integer> items = new LinkedBlockingQueue<>();
private MyBlockingQ items;
public Consumer(MyBlockingQ q) {
this.items = q;
}
public void run() {
while (true) {
items.remove();
//Thread.sleep(1000);
}
}
}
制片人
import java.util.Random;
public class Producer implements Runnable {
private MyBlockingQ items;
public Producer(MyBlockingQ q) {
this.items = q;
}
private int generateRandomNumber(int start, int end) {
Random rand = new Random();
int number = start + rand.nextInt(end - start + 1);
return number;
}
public void run() {
for (int i = 0; i < 5; i++) {
int rand = generateRandomNumber(100, 1000);
items.add(rand);
}
}
}
MyBlockingQ(共享資源)
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.logging.Level;
import java.util.logging.Logger;
public class MyBlockingQ {
private BlockingQueue<Integer> items = new LinkedBlockingQueue<>();
private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
public MyBlockingQ() {
}
public void add(Integer i) {
lock.writeLock().lock();
try {
items.put(i);
System.out.println("Producing " + i + " " + Thread.currentThread().getName() + " size left " + items.size());
} catch (InterruptedException ex) {
Logger.getLogger(ProducerConsumer.class.getName()).log(Level.SEVERE, null, ex);
} finally {
lock.writeLock().unlock();
}
}
public void remove() {
lock.writeLock().lock();
try {
int taken = items.take();
System.out.println("Consuming " + taken + " " + Thread.currentThread().getName() + " size left " + items.size());
} catch (InterruptedException ex) {
Logger.getLogger(ProducerConsumer.class.getName()).log(Level.SEVERE, null, ex);
} finally {
lock.writeLock().unlock();
}
}
}
測試
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
public class ProducerConsumer {
public static void main(String args[]) {
MyBlockingQ items = new MyBlockingQ();
System.out.println("starting");
Thread t1 = new Thread(new Producer(items));
Thread t2 = new Thread(new Producer(items));
Thread t3 = new Thread(new Consumer(items));
Thread t4 = new Thread(new Consumer(items));
t1.start();
t2.start();
t3.start();
t4.start();
}
}
這兩行
items.put(rand);
System.out.println("Producing " + rand + " " + Thread.currentThread().getName() + " size left " + items.size());
沒有同步。 生產者可能會將數字放入隊列中,但是當從放入其中的線程顯示隊列的大小時,消費者可能已經消耗了一個數字。
你可能會對這部分輸出感到困惑:
Producing 425 Thread-0 size left 0
Consuming 890 Thread-3 size left 0
Consuming 425 Thread-2 size left 0
Producing 890 Thread-1 size left 0
問題:在Thread-1產生之前,Thread-3如何消耗890個項目?
答案: Thread-3在生成之前不會消耗Thread-1中的項目。
原因:當Thread-1將項目放入隊列時,Thread-3可能已經在等待從隊列中獲取的項目。 所以Thread-1放置物品:
items.put(rand);
並且在線程1之前跳轉到下一行並打印有關它生成的項目的信息,線程3執行以下行:
System.out.println("Consuming " + items.take() + " " + Thread.currentThread().getName() + " size left " + items.size());
只有這時Thread-1才會執行println:
System.out.println("Producing " + rand + " " + Thread.currentThread().getName() + " size left " + items.size());
因此,您可以在控制台中看到這些有趣的結果。
您可能想要閱讀有關同步的內容 。 有兩種方法可以解決您的問題:
同步鎖定對同步塊內對象的訪問。 這意味着每個其他方法必須等待輪到它才能訪問對象。
因此,如果您對Producer和Consumer中的項目使用同步,那么:
我的情況是當item為空且Consumer的方法鎖定項目時,程序將陷入所謂的死鎖 。 制作人必須等待消費者解鎖 ,但它永遠不會發生,因為消費者正在等待采取物品(必須由生產者放置)。
此外,我對生產者和消費者都進行了2秒鍾的睡眠,但在測試時,每兩秒就會打印出2個生產者和2個消費者的結果。
這是你應該期待的。 在Test類中,您將生產2個生產者和2個消費者。
Thread t1 = new Thread(producer);
Thread t2 = new Thread(producer);
Thread t3 = new Thread(consumer);
Thread t4 = new Thread(consumer);
t1.start();
t2.start();
t3.start();
t4.start();
您需要同步items
訪問權限。 我只是略微改變了你的例子,結果看起來不錯。 由於同步,您還必須處理死鎖。 在這種情況下,只要您不在Consumer
的items.take()
進行同步就應該沒問題。
你的新測試:
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
public class ProducerConsumer {
public static void main(String args[]) {
BlockingQueue<Integer> items = new LinkedBlockingQueue<>();
Thread t1 = new Thread(new Producer(items));
Thread t2 = new Thread(new Producer(items));
Thread t3 = new Thread(new Consumer(items));
Thread t4 = new Thread(new Consumer(items));
t1.start();
t2.start();
t3.start();
t4.start();
}
}
消費者
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Consumer implements Runnable {
BlockingQueue<Integer> items = new LinkedBlockingQueue<>();
public Consumer(BlockingQueue<Integer> q) {
this.items = q;
}
public void run() {
while (true) {
try {
System.out.println("Consuming " + items.take() + " " + Thread.currentThread().getName() + " size left " + items.size());
Thread.sleep(1000);
} catch (InterruptedException ex) {
Logger.getLogger(ProducerConsumer.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
和制片人
import java.util.Random;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Producer implements Runnable {
BlockingQueue<Integer> items = new LinkedBlockingQueue<>();
public Producer(BlockingQueue<Integer> q) {
this.items = q;
}
private int generateRandomNumber(int start, int end) {
Random rand = new Random();
int number = start + rand.nextInt(end - start + 1);
return number;
}
public void run() {
for (int i = 0; i < 5; i++) {
int rand = generateRandomNumber(100, 1000);
try {
synchronized (items) {
items.put(rand);
System.out.println("Producing " + rand + " " + Thread.currentThread().getName() + " size left " + items.size());
}
Thread.sleep(1000);
} catch (InterruptedException ex) {
Logger.getLogger(ProducerConsumer.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
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