如何在scrapy中合并多进程

import scrapy
from scrapy.crawler import CrawlerProcess
from multiprocessing import Process, Queue

class MySpider(scrapy.Spider):
    name = 'myspider'
    start_urls = ['http://example.com/page1', 'http://example.com/page2', 'http://example.com/page3']

    def parse(self, response):
        # 解析网页内容的代码

def worker(queue):
    process = CrawlerProcess()
    process.crawl(MySpider)
    process.start()
    queue.put(None)

def merge_results(queue):
    results = []
    while True:
        result = queue.get()
        if result is None:
            break
        results.append(result)
    # 合并结果的代码

if __name__ == '__main__':
    queue = Queue()
    p1 = Process(target=worker, args=(queue,))
    p2 = Process(target=worker, args=(queue,))
    p3 = Process(target=worker, args=(queue,))
    p4 = Process(target=merge_results, args=(queue,))

    p1.start()
    p2.start()
    p3.start()
    p4.start()

    p1.join()
    p2.join()
    p3.join()
    p4.join()