Napajs demo-多个生产者/消费者

生产者/消费者问题

多生产者和多消费者

多个生产者向一个缓冲区中存入数据，多个生产者从缓冲区中取数据。这是有界缓冲区问题，队列改写，生产者之间、消费者之间、生产者消费者之间互相互斥。 共享缓冲区作为一个环绕缓冲区，存数据到尾时再从头开始。

• 我们使用一个互斥量保护生产者向缓冲区中存入数据。由于有多个生产者，因此需要记住现在向缓冲区中存入的位置。
• 使用一个互斥量保护缓冲区中消息的数目，这个生产的数据数目作为生产者和消费者沟通的桥梁。 使
• 用一个条件变量用于唤醒消费者。由于有多个消费者，同样消费者也需要记住每次取的位置。

在选项中选择生产条目的数目，生产者的线程数目，消费者的线程数目。生产者将条目数目循环放入缓冲区中，消费者从缓冲区中循环取出并在屏幕上打印出来。

以上内容来自简书

作者：穹蓝奥义

链接：http://www.jianshu.com/p/b16296e9ac85

來源：简书

JavaScript实现多生产者和多消费者问题

使用napajs的来实现多生产者和多消费者问题

先使用npm安装napajs

npm install napajs

代码：

let napa = require('napajs');

/**
 * producer 和 consumer 两个zone（也就是两个进程）
 * 生产者和消费者各创建两个worker（相当于两个线程）
 */
let producer = napa.zone.create('producer', { workers: 2 });
let consumer = napa.zone.create('consumer', { workers: 2 });

let store = napa.store.create('store1');
store.set('mutex', true);
store.set('empty', 2);
store.set('full', 0);
store.set('list', '');

function sleep(time) {
  return new Promise((resolve) => setTimeout(resolve, time));
}

/**
 * 生产
 * @param index 生产者编号
 */
function produce(index) {
  while (1) {
    while (store.get('empty') === 0) {
      sleep(1000);
    }
    store.set('empty', store.get('empty') - 1);
    while (!store.get('mutex')) {
      sleep(1000);
    }
    store.set('mutex', false);
    console.log('producer ' + index + ' produce a product');
    let list = '';
    list = store.get('list') + '1';
    store.set('list', list);
    console.log('add to buffer');
    store.set('mutex', true);
    store.set('full', store.get('full') + 1);
  }
}

/**
 * 消费
 * @param index 消费者编号
 */
function consume(index) {
  while (1) {
    while (store.get('full') === 0) {
      sleep(1000);
    }
    store.set('full', store.get('full') - 1);
    while (!store.get('mutex')) {
      sleep(1000);
    }
    store.set('mutex', false);
    let list = store.get('list');
    list = list.substr(1);
    store.set('list', list);
    console.log('consumer ' + index + ' get a product from buffer');
    store.set('mutex', true);
    store.set('empty', store.get('empty') + 1);
    console.log('consume a product');
  }

}

let mainProcess = () => {
  let code = 'let napa = require("napajs");\n' +
    '  let store = napa.store.get(\'store1\');';

  //广播napa和store的声明代码
  producer.broadcast(code)
    .then(() => {
      console.log('producer broadcast success');
    }).catch(error => {
    console.log(error);
  });
  consumer.broadcast(code)
    .then(() => {
      console.log('consumer broadcast success');
    }).catch(error => {
    console.log(error);
  });

  //广播sleep、produce、consume等函数声明到napa workers
  producer.broadcast(sleep.toString());
  consumer.broadcast(sleep.toString());
  producer.broadcast(produce.toString());
  consumer.broadcast(consume.toString());

  //执行两个produce
  producer.execute('', 'produce',[1])
    .then((result) => {
      console.log('producer execute,' + result.value);
    })
    .catch((error) => {
      console.log(error);
    });
  producer.execute('', 'produce',[2])
    .then((result) => {
      console.log('producer execute,' + result.value);
    })
    .catch((error) => {
      console.log(error);
    });
  //执行两个consume
  consumer.execute('', 'consume',[1])
    .then((result) => {
      console.log('consumer execute,' + result.value);
    })
    .catch((error) => {
      console.log(error);
    });
  consumer.execute('', 'consume',[2])
    .then((result) => {
      console.log('consumer execute,' + result.value);
    })
    .catch((error) => {
      console.log(error);
    });
};
mainProcess();

输出

"F:\WebStorm\WebStorm 2017.2.2\bin\runnerw.exe" F:\nodejs\node.exe F:\WebStorm\practices\jsDoc-demo\producerConsumer.js
producer 2 produce a product
add to buffer
producer 2 produce a product
add to buffer
producer 1 produce a product
add to buffer
producer 2 produce a product
add to buffer
consumer 1 get a product from buffer
producer 2 produce a product
consume a product
add to buffer
consumer 2 get a product from buffer
consume a product
consumer 1 get a product from buffer
consume a product
producer 2 produce a product
add to buffer
consumer 2 get a product from buffer
producer 1 produce a product
consume a product
add to buffer
producer 2 produce a product
add to buffer
consumer 1 get a product from buffer
consumer 2 get a product from buffer
consume a product
consume a product
producer 2 produce a product
consumer 1 get a product from buffer
add to buffer
...