Scrapy Limit Requests For Testing

Question

I\'ve been searching the scrapy documentation for a way to limit the number of requests my spiders are allowed to make. During development I don\'t want to sit here and wait

Answer 1

As an addition to @alecxe's answer, it's worth noting that:

Requests which are currently in the downloader queue (up to CONCURRENT_REQUESTS requests) are still processed.

Although the above documentation is currently present only for CLOSESPIDER_ITEMCOUNT (and not CLOSESPIDER_PAGECOUNT), it should also appear there, because that's how it works.

One can verify it with the following code:

# scraper.py

from scrapy import Spider
from scrapy import Request

class MySpider(Spider):
    name = 'MySpider'
    custom_settings = {'CLOSESPIDER_PAGECOUNT': 2}

    def start_requests(self):
        data_urls = [
          'https://www.example.com', 'https://www.example1.com', 'https://www.example2.com'
        ]
        for url in data_urls:
            yield Request(url=url, callback=lambda res: print(res))

Assuming all 3 requests were yielded before two responses were already returned (this happened to me in 100% of times I tested it), the third request (to example2.com) would still get executed, so that running it:

scrapy runspider scraper.py

... will output (note how although the spider went into a Closing spider stage, GET https://example2.com was still executed):

INFO: Scrapy 2.3.0 started (bot: scrapybot)  
[...]  
INFO: Overridden settings:  
{'CLOSESPIDER_PAGECOUNT': 2, 'SPIDER_LOADER_WARN_ONLY': True}
[...]  
INFO: Spider opened
[...]
DEBUG: Crawled (200)  (referer: None)
<200 https://www.example.com>
DEBUG: Crawled (200)  (referer: None)
INFO: Closing spider (closespider_pagecount)
<200 https://www.example1.com>
DEBUG: Redirecting (301) to  from 
INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 647,
 'downloader/request_count': 3,
 'downloader/request_method_count/GET': 3,
 'downloader/response_bytes': 3659,
 'downloader/response_count': 3,
 'downloader/response_status_count/200': 2,
 'downloader/response_status_count/301': 1,
 'elapsed_time_seconds': 11.052137,
 'finish_reason': 'closespider_pagecount',
 'finish_time': datetime.datetime(2020, 10, 4, 11, 28, 41, 801185),
 'log_count/DEBUG': 3,
 'log_count/INFO': 10,
 'response_received_count': 2,
 'scheduler/dequeued': 3,
 'scheduler/dequeued/memory': 3,
 'scheduler/enqueued': 4,
 'scheduler/enqueued/memory': 4,
 'start_time': datetime.datetime(2020, 10, 4, 11, 28, 30, 749048)}
INFO: Spider closed (closespider_pagecount)

This can be prevented by simply introducing an instance variable (e.g., limit):

from scrapy import Spider
from scrapy import Request

class MySpider(Spider):
    name = 'MySpider'
    limit = 2

    def start_requests(self):
        data_urls = [
           'https://www.example.com', 'https://www.example1.com', 'https://www.example2.com'
        ]
        for url in data_urls:
            if self.limit > 0:
                yield Request(url=url, callback=lambda res: print(res))
                self.limit -= 1

So that now only 2 requests are queued and executed. Output:

[...]
DEBUG: Crawled (200)  (referer: None)
<200 https://www.example.com>
DEBUG: Crawled (200)  (referer: None)
<200 https://www.example1.com>
INFO: Closing spider (closespider_pagecount)
INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 431,
 'downloader/request_count': 2,
 'downloader/request_method_count/GET': 2,
 'downloader/response_bytes': 3468,
 'downloader/response_count': 2,
 'downloader/response_status_count/200': 2,
 'elapsed_time_seconds': 5.827646,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2020, 10, 4, 11, 29, 41, 801185),
 'log_count/DEBUG': 2,
 'log_count/INFO': 10,
 'response_received_count': 2,
 'scheduler/dequeued': 2,
 'scheduler/dequeued/memory': 2,
 'scheduler/enqueued': 2,
 'scheduler/enqueued/memory': 2,
 'start_time': datetime.datetime(2020, 10, 4, 11, 29, 30, 749048)}
INFO: Spider closed (finished)