Scrapy - delay requests in spider callbacks

delayspider.py

from scrapy.spider import BaseSpider
from twisted.internet import reactor, defer
from scrapy.http import Request

DELAY = 5 # seconds


class MySpider(BaseSpider):

    name = 'wikipedia'
    max_concurrent_requests = 1

    start_urls = ['http://www.wikipedia.org']

    def parse(self, response):
        nextreq = Request('http://en.wikipedia.org')
        dfd = defer.Deferred()
        reactor.callLater(DELAY, dfd.callback, nextreq)
        return dfd

gistfile1.sh

$ scrapy runspider delayspider.py 
2012-05-24 11:01:54-0300 [scrapy] INFO: Scrapy 0.15.1 started (bot: scrapybot)
2012-05-24 11:01:54-0300 [scrapy] DEBUG: Enabled extensions: LogStats, TelnetConsole, CloseSpider, WebService, CoreStats, SpiderState
2012-05-24 11:01:54-0300 [scrapy] DEBUG: Enabled downloader middlewares: HttpAuthMiddleware, DownloadTimeoutMiddleware, UserAgentMiddleware, RetryMiddleware, DefaultHeadersMiddleware, RedirectMiddleware, CookiesMiddleware, HttpCompressionMiddleware, ChunkedTransferMiddleware, DownloaderStats
2012-05-24 11:01:54-0300 [scrapy] DEBUG: Enabled spider middlewares: HttpErrorMiddleware, OffsiteMiddleware, RefererMiddleware, UrlLengthMiddleware, DepthMiddleware
2012-05-24 11:01:54-0300 [scrapy] DEBUG: Enabled item pipelines: 
2012-05-24 11:01:54-0300 [wikipedia] INFO: Spider opened
2012-05-24 11:01:54-0300 [wikipedia] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2012-05-24 11:01:54-0300 [scrapy] DEBUG: Telnet console listening on 0.0.0.0:6023
2012-05-24 11:01:54-0300 [scrapy] DEBUG: Web service listening on 0.0.0.0:6080
2012-05-24 11:01:56-0300 [wikipedia] DEBUG: Crawled (200) <GET http://www.wikipedia.org> (referer: None)
2012-05-24 11:02:04-0300 [wikipedia] DEBUG: Redirecting (301) to <GET http://en.wikipedia.org/wiki/Main_Page> from <GET http://en.wikipedia.org>
2012-05-24 11:02:06-0300 [wikipedia] DEBUG: Crawled (200) <GET http://en.wikipedia.org/wiki/Main_Page> (referer: http://www.wikipedia.org)
2012-05-24 11:02:11-0300 [wikipedia] INFO: Closing spider (finished)
2012-05-24 11:02:11-0300 [wikipedia] INFO: Dumping spider stats:
	{'downloader/request_bytes': 745,
	 'downloader/request_count': 3,
	 'downloader/request_method_count/GET': 3,
	 'downloader/response_bytes': 29304,
	 'downloader/response_count': 3,
	 'downloader/response_status_count/200': 2,
	 'downloader/response_status_count/301': 1,
	 'finish_reason': 'finished',
	 'finish_time': datetime.datetime(2012, 5, 24, 14, 2, 11, 447498),
	 'request_depth_max': 2,
	 'scheduler/memory_enqueued': 3,
	 'start_time': datetime.datetime(2012, 5, 24, 14, 1, 54, 408882)}
2012-05-24 11:02:11-0300 [wikipedia] INFO: Spider closed (finished)
2012-05-24 11:02:11-0300 [scrapy] INFO: Dumping global stats:
	{}

I know it's outdated, by why not use download_delay attribute?

class MySpider(BaseSpider):

    name = 'wikipedia'
    download_delay = 5

Or you can just set DOWNLOAD_DELAY = 5 in settings.py