我的扩展中未收到 Scrapy spider_idle 信号

Question

我spider_idle在接收信号时的几个蜘蛛之间有共同的行为，我想将此行为移动到扩展中。

我的分机已经成功侦听spider_opened并spider_closed发出信号。但是，spider_idle没有接收到信号。

这是我的扩展程序（为简洁起见进行了编辑）：

import logging
import MySQLdb
import MySQLdb.cursors
from scrapy import signals

logger = logging.getLogger(__name__)

class MyExtension(object):

    def __init__(self, settings, stats):
        self.settings = settings
        self.stats = stats

    @classmethod
    def from_crawler(cls, crawler):

        # instantiate the extension object
        ext = cls(crawler.settings, crawler.stats)

        # connect the extension object to signals
        crawler.signals.connect(ext.spider_opened, signal=signals.spider_opened)
        crawler.signals.connect(ext.spider_closed, signal=signals.spider_closed)
        crawler.signals.connect(ext.spider_idle, signal=signals.spider_idle)

        # return the extension object
        return ext

    def spider_opened(self, spider):
        logger.info("start logging spider %s", spider.name)

    def spider_closed(self, spider):
        logger.info("end logging spider %s", spider.name)

    def spider_idle(self, spider):
        logger.info("idle logging spider %s", spider.name)

        # attempt to crawl orphaned products
        db = MySQLdb.connect(host=self.settings['AWS_RDS_HOST'],
                             port=self.settings['AWS_RDS_PORT'],
                             user=self.settings['AWS_RDS_USER'],
                             passwd=self.settings['AWS_RDS_PASSWD'],
                             db=self.settings['AWS_RDS_DB'],
                             cursorclass=MySQLdb.cursors.DictCursor,
                             use_unicode=True,
                             charset="utf8",)
        c=db.cursor()

        c.execute("""SELECT p.url FROM products p LEFT JOIN product_data pd ON p.id = pd.product_id AND pd.scrape_date = CURDATE() WHERE p.website_id = %s AND pd.id IS NULL""", (spider.website_id,))

        while True:
            product = c.fetchone()
            if product is None:
                break
            # record orphaned product
            self.stats.inc_value('orphaned_count')
            yield self.crawler.engine.crawl(Request(url=product['url'], callback=spider.parse_item), spider)
        db.close()

为什么收不到信号？

更新

根据要求，这里有更多信息。

这是我的settings.py：

BOT_NAME = 'myproject'

SPIDER_MODULES = ['myproject.spiders']
NEWSPIDER_MODULE = 'myproject.spiders'

DOWNLOADER_MIDDLEWARES = {
    'rotating_proxies.middlewares.RotatingProxyMiddleware': 610,
    'rotating_proxies.middlewares.BanDetectionMiddleware': 620,
}

AUTOTHROTTLE_ENABLED = True
AUTOTHROTTLE_START_DELAY = 2
AUTOTHROTTLE_MAX_DELAY = 30
AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0 

EXTENSIONS = {
    'myproject.extensions.MyExtension': 500,
}

无论是否启用rotating_proxy中间件，我都会遇到同样的问题。

这是我正在测试的示例蜘蛛：

import scrapy
from furl import furl
from scrapy.http.request import Request
from scrapy.spiders import CrawlSpider, Rule
from scrapy.linkextractors import LinkExtractor
from myproject.items import MyProjectItem


class ScrapeThisSpider(CrawlSpider):
    name = "scrapethis"
    website_id = 5
    custom_settings = {
        'IMAGES_STORE': 's3://myproject-dev/images/scrapethis/',
        'LOG_FILE': 'scrapethis.log',
        'LOG_LEVEL': 'DEBUG',
    }
    allowed_domains = ['scrapethis.co.uk']
    start_urls = ['https://www.scrapethis.co.uk']

    def start_requests(self):
        for url in self.start_urls:
            yield Request(url, dont_filter=True)

    def customise_url(link):
        f = furl(link)
        f.args['ar'] = '3'
        return f.url

    rules = (
        Rule(LinkExtractor(allow=(), deny=('articleId=', ), process_value=customise_url)),
        Rule(LinkExtractor(allow=('articleId=', ), process_value=customise_url), callback='parse_item'),
    )

    def parse_item(self, response):
        price = response.xpath("//article[@class='productbox'] //strong[@class='pricefield__price']//text()").extract()

        item = MyProjectItem()
        f = furl(response.url)
        item['id'] = f.args['articleId']
        item['spider'] = self.name
        item['price'] = price
        return item

更新 2

我想我已经发现了导致spider_idle信号失败的原因 - 在我的方法中，我连接到 Amazon RDS 数据库，查询它并处理结果。

如果我注释掉代码，我的信号就会运行（我得到日志条目），如果我的查询代码仍然存在，信号就不会运行（或者至少，我没有得到日志条目）。

很奇怪，因为我在我的方法中做的第一件事就是记录信号？

更新 3

我发现如果我yield在查询结果循环中删除关键字，它可以工作 - 但只发出 1 个请求。我需要将查询中返回的每个 url 添加到爬虫中。（抱歉，如果我问了一些愚蠢的问题 - 我对 Python 和 scrapy 还是比较陌生）。