ReactorNotRestartable error in while loop with scrapy

Question

I get twisted.internet.error.ReactorNotRestartable error when I execute following code:

from time import sleep
from scrapy import signals
from scrapy.crawler import CrawlerProcess
from scrapy.utils.project import get_project_settings
from scrapy.xlib.pydispatch import dispatcher

result = None

def set_result(item):
    result = item

while True:
    process = CrawlerProcess(get_project_settings())
    dispatcher.connect(set_result, signals.item_scraped)

    process.crawl('my_spider')
    process.start()

    if result:
        break
    sleep(3)

For the first time it works, then I get error. I create process variable each time, so what's the problem?

Answer 1

By default, CrawlerProcess's .start() will stop the Twisted reactor it creates when all crawlers have finished.

You should call process.start(stop_after_crawl=False) if you create process in each iteration.

Another option is to handle the Twisted reactor yourself and use CrawlerRunner. The docs have an example on doing that.