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twisted.internet.error.ReactorAlreadyInstalledError: reactor already installed

I am having this error when I run a crawl process multiples times.
I am using scrapy 2.6
This is my code:
from scrapy.crawler import CrawlerProcess
from football.spiders.laliga import LaligaSpider
from scrapy.utils.project import get_project_settings
process = CrawlerProcess(settings=get_project_settings())
for i in range(1, 29):
process.crawl(LaligaSpider, **{'week': i})
process.start()

For me this worked, I put it before the CrawlerProcess
import sys
if "twisted.internet.reactor" in sys.modules:
del sys.modules["twisted.internet.reactor"]

This solution avoids use of CrawlerProcess as stated in the docs.
https://docs.scrapy.org/en/latest/topics/practices.html#run-scrapy-from-a-script
There’s another Scrapy utility that provides more control over the crawling process: scrapy.crawler.CrawlerRunner. This class is a thin wrapper that encapsulates some simple helpers to run multiple crawlers, but it won’t start or interfere with existing reactors in any way.
It’s recommended you use CrawlerRunner instead of CrawlerProcess if your application is already using Twisted and you want to run Scrapy in the same reactor.
from twisted.internet import reactor
from scrapy.crawler import CrawlerRunner
from scrapy.utils.project import get_project_settings
from scrapy.utils.log import configure_logging
from football.spiders.laliga import LaligaSpider
# Enable logging for CrawlerRunner
configure_logging()
runner = CrawlerRunner(settings=get_project_settings())
for i in range(1, 29):
runner.crawl(LaligaSpider, **{'week': i})
deferred = runner.join()
deferred.addBoth(lambda _: reactor.stop())
reactor.run() # the script will block here until all crawling jobs are finished

I've just run into this issue as well. It appears that the docs at https://docs.scrapy.org/en/latest/topics/practices.html are incorrect in stating that CrawlerProcess can be used to run multiple crawlers built with spiders, since each new crawler attempts to load a new reactor instance if you give it a spider. I was able to get my code to work by using CrawlerRunner instead, as also detailed on the same page.
import scrapy
from twisted.internet import reactor
from scrapy.crawler import CrawlerRunner
from scrapy.utils.log import configure_logging
from scrapy.utils.project import get_project_settings
class MySpider1(scrapy.Spider):
# Your first spider definition
...
class MySpider2(scrapy.Spider):
# Your second spider definition
...
configure_logging()
settings = get_project_settings() # settings not required if running
runner = CrawlerRunner(settings) # from script, defaults provided
runner.crawl(MySpider1) # your loop would go here
runner.crawl(MySpider2)
d = runner.join()
d.addBoth(lambda _: reactor.stop())
reactor.run() # the script will block here until all crawling jobs are finished

I have encountered this problem, but it is solved after updating both Scrapy and Twisted.
the current version of the packages.
Twisted==22.8.0
Scrapy==2.6.2

Chain Scrapy Spiders which have data dependencies in a twisted reactor

Actually the scrapy docs explained how to chain two spyder like this
from twisted.internet import reactor, defer
from scrapy.crawler import CrawlerRunner
from scrapy.utils.log import configure_logging
class MySpider1(scrapy.Spider):
# Your first spider definition
...
class MySpider2(scrapy.Spider):
# Your second spider definition
...
configure_logging()
runner = CrawlerRunner()
#defer.inlineCallbacks
def crawl():
yield runner.crawl(MySpider1)
yield runner.crawl(MySpider2)
reactor.stop()
crawl()
reactor.run() # the script will block here until the last crawl call is finished
But in my use case, the MySpider2 need informations retrieved by MySpider1 after transformation using some transformFunction().
So i want something like this :
def transformFunction():
... transforme data retrieved by spyder1 ...
return newdata
def crawl():
yield runner.crawl(MySpider1)
newdata = transformFunction()
yield runner.crawl(MySpider2, data=newData)
reactor.stop()
What i want to be scheduled :
MySpider1 start, write data on disk then quit
transformFunction() transform data to newdata
MySpider2 start using the newData
So how can i manage this behavior using twisted reactor and scrapy ?

runner.crawl returns a Deferred so you could chain callbacks to it. Minor tweaks will have to be done to your code.
from twisted.internet import task
from scrapy.crawler import CrawlerRunner
from scrapy.utils.log import configure_logging
configure_logging()
def crawl(reactor):
runner = CrawlerRunner()
d = runner.crawl(MySpider1)
d.addCallback(transformFunction)
d.addCallback(crawl2, runner)
return d
def transformFunction(result):
# crawl doesn't usually return any results if successful so ignore result var here
# ...
return newdata
def crawl2(result, runner):
# result == newdata from transformFunction
# runner is passed in from crawl()
return runner.crawl(MySpider2, data=result)
task.react(crawl)
The main function is crawl(), it gets executed by task.react() which will start and stop the reactor for you. The Deferred is returned from runner.crawl() and the transformFunction + crawl2 functions are chained to it so that when a function completes, the next one starts.

Easiest way to run scrapy crawler so it doesn't block the script

The official docs give many ways for running scrapy crawlers from code:
import scrapy
from scrapy.crawler import CrawlerProcess
class MySpider(scrapy.Spider):
# Your spider definition
...
process = CrawlerProcess({
'USER_AGENT': 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)'
})
process.crawl(MySpider)
process.start() # the script will block here until the crawling is finished
But all of them block script until crawling is finished. What's the easiest way in python to run the crawler in a non-blocking, async manner?

I tried every solution I could find, and the only working for me was this. But in order to make it work with scrapy 1.1rc1 I had to tweak it a little bit:
from scrapy.crawler import Crawler
from scrapy import signals
from scrapy.utils.project import get_project_settings
from twisted.internet import reactor
from billiard import Process
class CrawlerScript(Process):
def __init__(self, spider):
Process.__init__(self)
settings = get_project_settings()
self.crawler = Crawler(spider.__class__, settings)
self.crawler.signals.connect(reactor.stop, signal=signals.spider_closed)
self.spider = spider
def run(self):
self.crawler.crawl(self.spider)
reactor.run()
def crawl_async():
spider = MySpider()
crawler = CrawlerScript(spider)
crawler.start()
crawler.join()
So now when I call crawl_async, it starts crawling and doesn't block my current thread. I'm absolutely new to scrapy, so may be this isn't a very good solution but it worked for me.
I used these versions of the libraries:
cffi==1.5.0
Scrapy==1.1rc1
Twisted==15.5.0
billiard==3.3.0.22

Netimen's answer is correct. process.start() calls reactor.run(), which blocks the thread. Just that I don't think it is necessary to subclass billiard.Process. Although poorly documented, billiard.Process does have a set of APIs to call another function asynchronously without subclassing.
from scrapy.crawler import CrawlerProcess
from scrapy.utils.project import get_project_settings
from billiard import Process
crawler = CrawlerProcess(get_project_settings())
process = Process(target=crawler.start, stop_after_crawl=False)
def crawl(*args, **kwargs):
crawler.crawl(*args, **kwargs)
process.start()
Note that if you don't have stop_after_crawl=False, you may run into ReactorNotRestartable exception when you run the crawler for more than twice.

cannot import scrapy modules as library

I'm trying to run spiders from python script following scrapy document: http://doc.scrapy.org/en/latest/topics/practices.html
from twisted.internet import reactor
from scrapy.crawler import Crawler
from scrapy import log, signals
from testspiders.spiders.followall import FollowAllSpider
from scrapy.utils.project import get_project_settings
spider = FollowAllSpider(domain='scrapinghub.com')
settings = get_project_settings()
crawler = Crawler(settings)
crawler.signals.connect(reactor.stop, signal=signals.spider_closed)
crawler.configure()
crawler.crawl(spider)
crawler.start()
log.start()
reactor.run() # the script will block here until the spider_closed signal was sent
But python just cannot import the module, the error looks like this:
Traceback (most recent call last):
...
from scrapy.crawler import Crawler
File "aappp/scrapy.py", line 1, in <module>
ImportError: No module named crawler
The issue is briefly mentioned in faq of scrapy document, but it doesn't help too much for me.

Have you tried doing it this way?
from scrapy.project import crawler
(That's how it's done on http://doc.scrapy.org/en/latest/faq.html - looks like they already answered your question there.)
It also gives a more recent way of doing it and calls this previous method deprecated:
"This way to access the crawler object is deprecated, the code should be ported to use from_crawler class method, for example:
class SomeExtension(object):
#classmethod
def from_crawler(cls, crawler):
o = cls()
o.crawler = crawler
return o
"

Locally run all of the spiders in Scrapy

Is there a way to run all of the spiders in a Scrapy project without using the Scrapy daemon? There used to be a way to run multiple spiders with scrapy crawl, but that syntax was removed and Scrapy's code changed quite a bit.
I tried creating my own command:
from scrapy.command import ScrapyCommand
from scrapy.utils.misc import load_object
from scrapy.conf import settings
class Command(ScrapyCommand):
requires_project = True
def syntax(self):
return '[options]'
def short_desc(self):
return 'Runs all of the spiders'
def run(self, args, opts):
spman_cls = load_object(settings['SPIDER_MANAGER_CLASS'])
spiders = spman_cls.from_settings(settings)
for spider_name in spiders.list():
spider = self.crawler.spiders.create(spider_name)
self.crawler.crawl(spider)
self.crawler.start()
But once a spider is registered with self.crawler.crawl(), I get assertion errors for all of the other spiders:
Traceback (most recent call last):
File "/usr/lib/python2.7/site-packages/scrapy/cmdline.py", line 138, in _run_command
cmd.run(args, opts)
File "/home/blender/Projects/scrapers/store_crawler/store_crawler/commands/crawlall.py", line 22, in run
self.crawler.crawl(spider)
File "/usr/lib/python2.7/site-packages/scrapy/crawler.py", line 47, in crawl
return self.engine.open_spider(spider, requests)
File "/usr/lib/python2.7/site-packages/twisted/internet/defer.py", line 1214, in unwindGenerator
return _inlineCallbacks(None, gen, Deferred())
--- <exception caught here> ---
File "/usr/lib/python2.7/site-packages/twisted/internet/defer.py", line 1071, in _inlineCallbacks
result = g.send(result)
File "/usr/lib/python2.7/site-packages/scrapy/core/engine.py", line 215, in open_spider
spider.name
exceptions.AssertionError: No free spider slots when opening 'spidername'
Is there any way to do this? I'd rather not start subclassing core Scrapy components just to run all of my spiders like this.

Why didn't you just use something like:
scrapy list|xargs -n 1 scrapy crawl
?

Here is an example that does not run inside a custom command, but runs the Reactor manually and creates a new Crawler for each spider:
from twisted.internet import reactor
from scrapy.crawler import Crawler
# scrapy.conf.settings singlton was deprecated last year
from scrapy.utils.project import get_project_settings
from scrapy import log
def setup_crawler(spider_name):
crawler = Crawler(settings)
crawler.configure()
spider = crawler.spiders.create(spider_name)
crawler.crawl(spider)
crawler.start()
log.start()
settings = get_project_settings()
crawler = Crawler(settings)
crawler.configure()
for spider_name in crawler.spiders.list():
setup_crawler(spider_name)
reactor.run()
You will have to design some signal system to stop the reactor when all spiders are finished.
EDIT: And here is how you can run multiple spiders in a custom command:
from scrapy.command import ScrapyCommand
from scrapy.utils.project import get_project_settings
from scrapy.crawler import Crawler
class Command(ScrapyCommand):
requires_project = True
def syntax(self):
return '[options]'
def short_desc(self):
return 'Runs all of the spiders'
def run(self, args, opts):
settings = get_project_settings()
for spider_name in self.crawler.spiders.list():
crawler = Crawler(settings)
crawler.configure()
spider = crawler.spiders.create(spider_name)
crawler.crawl(spider)
crawler.start()
self.crawler.start()

the answer of #Steven Almeroth will be failed in Scrapy 1.0, and you should edit the script like this:
from scrapy.commands import ScrapyCommand
from scrapy.utils.project import get_project_settings
from scrapy.crawler import CrawlerProcess
class Command(ScrapyCommand):
requires_project = True
excludes = ['spider1']
def syntax(self):
return '[options]'
def short_desc(self):
return 'Runs all of the spiders'
def run(self, args, opts):
settings = get_project_settings()
crawler_process = CrawlerProcess(settings)
for spider_name in crawler_process.spider_loader.list():
if spider_name in self.excludes:
continue
spider_cls = crawler_process.spider_loader.load(spider_name)
crawler_process.crawl(spider_cls)
crawler_process.start()

this code is works on My scrapy version is 1.3.3 (save it in same directory in scrapy.cfg):
from scrapy.utils.project import get_project_settings
from scrapy.crawler import CrawlerProcess
setting = get_project_settings()
process = CrawlerProcess(setting)
for spider_name in process.spiders.list():
print ("Running spider %s" % (spider_name))
process.crawl(spider_name,query="dvh") #query dvh is custom argument used in your scrapy
process.start()
for scrapy 1.5.x (so you don't get the deprecation warning)
from scrapy.utils.project import get_project_settings
from scrapy.crawler import CrawlerProcess
setting = get_project_settings()
process = CrawlerProcess(setting)
for spider_name in process.spider_loader.list():
print ("Running spider %s" % (spider_name))
process.crawl(spider_name,query="dvh") #query dvh is custom argument used in your scrapy
process.start()

Linux script
#!/bin/bash
for spider in $(scrapy list)
do
scrapy crawl "$spider" -o "$spider".json
done

Running all spiders in project using python
# Run all spiders in project implemented using Scrapy 2.7.0
from scrapy.crawler import CrawlerProcess
from scrapy.utils.project import get_project_settings
def main():
settings = get_project_settings()
process = CrawlerProcess(settings)
spiders_names = process.spider_loader.list()
for s in spiders_names:
process.crawl(s)
process.start()
if __name__ == '__main__':
main()