如何整合Flask＆amp; Scrapy？

时间：2016-04-03 10:25:39

标签： python flask scrapy

我正在使用scrapy来获取数据，我想使用flask web框架在网页中显示结果。但我不知道如何在烧瓶应用程序中调用蜘蛛。我曾尝试使用CrawlerProcess来调用我的蜘蛛，但我得到了这样的错误：

ValueError
ValueError: signal only works in main thread

Traceback (most recent call last)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/Library/Python/2.7/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/Library/Python/2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/Library/Python/2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/Users/Rabbit/PycharmProjects/Flask_template/FlaskTemplate.py", line 102, in index
process = CrawlerProcess()
File "/Library/Python/2.7/site-packages/scrapy/crawler.py", line 210, in __init__
install_shutdown_handlers(self._signal_shutdown)
File "/Library/Python/2.7/site-packages/scrapy/utils/ossignal.py", line 21, in install_shutdown_handlers
reactor._handleSignals()
File "/Library/Python/2.7/site-packages/twisted/internet/posixbase.py", line 295, in _handleSignals
_SignalReactorMixin._handleSignals(self)
File "/Library/Python/2.7/site-packages/twisted/internet/base.py", line 1154, in _handleSignals
signal.signal(signal.SIGINT, self.sigInt)
ValueError: signal only works in main thread

我的scrapy代码如下：

class EPGD(Item):

genID = Field()
genID_url = Field()
taxID = Field()
taxID_url = Field()
familyID = Field()
familyID_url = Field()
chromosome = Field()
symbol = Field()
description = Field()

class EPGD_spider(Spider):
    name = "EPGD"
    allowed_domains = ["epgd.biosino.org"]
    term = "man"
    start_urls = ["http://epgd.biosino.org/EPGD/search/textsearch.jsp?textquery="+term+"&submit=Feeling+Lucky"]

db = DB_Con()
collection = db.getcollection(name, term)

def parse(self, response):
    sel = Selector(response)
    sites = sel.xpath('//tr[@class="odd"]|//tr[@class="even"]')
    url_list = []
    base_url = "http://epgd.biosino.org/EPGD"

    for site in sites:
        item = EPGD()
        item['genID'] = map(unicode.strip, site.xpath('td[1]/a/text()').extract())
        item['genID_url'] = base_url+map(unicode.strip, site.xpath('td[1]/a/@href').extract())[0][2:]
        item['taxID'] = map(unicode.strip, site.xpath('td[2]/a/text()').extract())
        item['taxID_url'] = map(unicode.strip, site.xpath('td[2]/a/@href').extract())
        item['familyID'] = map(unicode.strip, site.xpath('td[3]/a/text()').extract())
        item['familyID_url'] = base_url+map(unicode.strip, site.xpath('td[3]/a/@href').extract())[0][2:]
        item['chromosome'] = map(unicode.strip, site.xpath('td[4]/text()').extract())
        item['symbol'] = map(unicode.strip, site.xpath('td[5]/text()').extract())
        item['description'] = map(unicode.strip, site.xpath('td[6]/text()').extract())
        self.collection.update({"genID":item['genID']}, dict(item),  upsert=True)
        yield item

    sel_tmp = Selector(response)
    link = sel_tmp.xpath('//span[@id="quickPage"]')

    for site in link:
        url_list.append(site.xpath('a/@href').extract())

    for i in range(len(url_list[0])):
        if cmp(url_list[0][i], "#") == 0:
            if i+1 < len(url_list[0]):
                print url_list[0][i+1]
                actual_url = "http://epgd.biosino.org/EPGD/search/" + url_list[0][i+1]
                yield Request(actual_url, callback=self.parse)
                break
            else:
                print "The index is out of range!"

我的烧瓶代码如下：

@app.route('/', methods=['GET', 'POST'])
def index():
    process = CrawlerProcess()
    process.crawl(EPGD_spider)
    return redirect(url_for('details'))


@app.route('/details', methods = ['GET'])
def epgd():
    if request.method == 'GET':
        results = db['EPGD_test'].find()
        json_results= []
        for result in results:
            json_results.append(result)
        return toJson(json_results)

使用烧瓶网框架时如何调用我的scrapy蜘蛛？

4 个答案:

答案 0 :(得分：22)

在蜘蛛面前添加HTTP服务器并不容易。有几种选择。

1。 Python子流程

如果您真的受限于Flask，如果您不能使用其他任何东西，只有将Scrapy与Flask集成的方法是为每个蜘蛛爬行启动外部进程，如其他答案建议的那样（请注意您的子进程需要在适当的Scrapy项目目录中产生）。

所有示例的目录结构应该如下所示，我使用dirbot test project 

> tree -L 1                                                                                                                                                              

├── dirbot
├── README.rst
├── scrapy.cfg
├── server.py
└── setup.py

这是在新流程中启动Scrapy的代码示例：

# server.py
import subprocess

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    """
    Run spider in another process and store items in file. Simply issue command:

    > scrapy crawl dmoz -o "output.json"

    wait for  this command to finish, and read output.json to client.
    """
    spider_name = "dmoz"
    subprocess.check_output(['scrapy', 'crawl', spider_name, "-o", "output.json"])
    with open("output.json") as items_file:
        return items_file.read()

if __name__ == '__main__':
    app.run(debug=True)

将上面保存为server.py并访问localhost：5000，您应该可以看到已删除的项目。

2。 Twisted-Klein + Scrapy

其他更好的方法是使用一些现有项目，将Twisted与Werkzeug集成，并显示类似于Flask的API，例如： Twisted-Klein。 Twisted-Klein允许您在与Web服务器相同的进程中异步运行您的蜘蛛。它更好，因为它不会阻止每个请求，它允许您简单地从HTTP路由请求处理程序返回Scrapy / Twisted延迟。

以下片段将Twisted-Klein与Scrapy集成，请注意您需要创建自己的CrawlerRunner基类，以便抓取工具收集项目并将其返回给调用者。此选项更高级，您在与Python服务器相同的过程中运行Scrapy蜘蛛，项目不存储在文件中但存储在内存中（因此没有像前面示例中那样的磁盘写入/读取）。最重要的是，它是异步的，并且它都在一个Twisted反应堆中运行。

# server.py
import json

from klein import route, run
from scrapy import signals
from scrapy.crawler import CrawlerRunner

from dirbot.spiders.dmoz import DmozSpider


class MyCrawlerRunner(CrawlerRunner):
    """
    Crawler object that collects items and returns output after finishing crawl.
    """
    def crawl(self, crawler_or_spidercls, *args, **kwargs):
        # keep all items scraped
        self.items = []

        # create crawler (Same as in base CrawlerProcess)
        crawler = self.create_crawler(crawler_or_spidercls)

        # handle each item scraped
        crawler.signals.connect(self.item_scraped, signals.item_scraped)

        # create Twisted.Deferred launching crawl
        dfd = self._crawl(crawler, *args, **kwargs)

        # add callback - when crawl is done cal return_items
        dfd.addCallback(self.return_items)
        return dfd

    def item_scraped(self, item, response, spider):
        self.items.append(item)

    def return_items(self, result):
        return self.items


def return_spider_output(output):
    """
    :param output: items scraped by CrawlerRunner
    :return: json with list of items
    """
    # this just turns items into dictionaries
    # you may want to use Scrapy JSON serializer here
    return json.dumps([dict(item) for item in output])


@route("/")
def schedule(request):
    runner = MyCrawlerRunner()
    spider = DmozSpider()
    deferred = runner.crawl(spider)
    deferred.addCallback(return_spider_output)
    return deferred


run("localhost", 8080)

将上面保存在文件server.py中并在Scrapy项目目录中找到它， 现在打开localhost：8080，它将启动dmoz spider并将以json格式删除的项目返回浏览器。

3。 ScrapyRT

当您尝试在蜘蛛面前添加HTTP应用程序时，会出现一些问题。例如，您有时需要处理蜘蛛日志（在某些情况下您可能需要它们），您需要以某种方式处理蜘蛛异常等。有些项目允许您以更简单的方式向蜘蛛添加HTTP API，例如ScrapyRT。这是一个将HTTP服务器添加到Scrapy蜘蛛并为您处理所有问题的应用程序（例如处理日志记录，处理蜘蛛错误等）。

所以在安装ScrapyRT后你只需要这样做：

> scrapyrt
在您的Scrapy项目目录中

，它将启动HTTP服务器侦听您的请求。然后，您访问http://localhost:9080/crawl.json?spider_name=dmoz&url=http://alfa.com它应该启动您的蜘蛛为您抓取给定的网址。

免责声明：我是ScrapyRt的作者之一。

答案 1 :(得分：1)

仅当您以自包含方式使用爬虫时，此方法才有效。 如何使用子进程模块和subprocess.call（）。

我用以下方式改变了你的蜘蛛，它起作用了。我没有数据库设置，因此这些行已被注释掉。 

    import scrapy 
from scrapy.crawler import CrawlerProcess
from scrapy.selector import Selector
from scrapy import Request


class EPGD(scrapy.Item):
    genID = scrapy.Field()
    genID_url = scrapy.Field()
    taxID = scrapy.Field()
    taxID_url = scrapy.Field()
    familyID = scrapy.Field()
    familyID_url = scrapy.Field()
    chromosome = scrapy.Field()
    symbol = scrapy.Field()
    description = scrapy.Field()

class EPGD_spider(scrapy.Spider):
    name = "EPGD"
    allowed_domains = ["epgd.biosino.org"]
    term = "man"
    start_urls = ["http://epgd.biosino.org/EPGD/search/textsearch.jsp?textquery="+term+"&submit=Feeling+Lucky"]


    def parse(self, response):
        sel = Selector(response)
        sites = sel.xpath('//tr[@class="odd"]|//tr[@class="even"]')
        url_list = []
        base_url = "http://epgd.biosino.org/EPGD"

        for site in sites:
            item = EPGD()
            item['genID'] = map(unicode.strip, site.xpath('td[1]/a/text()').extract())
            item['genID_url'] = base_url+map(unicode.strip, site.xpath('td[1]/a/@href').extract())[0][2:]
            item['taxID'] = map(unicode.strip, site.xpath('td[2]/a/text()').extract())
            item['taxID_url'] = map(unicode.strip, site.xpath('td[2]/a/@href').extract())
            item['familyID'] = map(unicode.strip, site.xpath('td[3]/a/text()').extract())
            item['familyID_url'] = base_url+map(unicode.strip, site.xpath('td[3]/a/@href').extract())[0][2:]
            item['chromosome'] = map(unicode.strip, site.xpath('td[4]/text()').extract())
            item['symbol'] = map(unicode.strip, site.xpath('td[5]/text()').extract())
            item['description'] = map(unicode.strip, site.xpath('td[6]/text()').extract())
            #self.collection.update({"genID":item['genID']}, dict(item),  upsert=True)
            yield item

            sel_tmp = Selector(response)
            link = sel_tmp.xpath('//span[@id="quickPage"]')

            for site in link:
                url_list.append(site.xpath('a/@href').extract())

            for i in range(len(url_list[0])):
                if cmp(url_list[0][i], "#") == 0:
                    if i+1 < len(url_list[0]):
                        print url_list[0][i+1]
                        actual_url = "http://epgd.biosino.org/EPGD/search/" + url_list[0][i+1]
                        yield Request(actual_url, callback=self.parse)
                        break
                    else:
                        print "The index is out of range!"



process = CrawlerProcess()
process.crawl(EPGD_spider)
process.start()

您应该可以在以下位置运行上述内容：

subprocess.check_output(['scrapy', 'runspider', "epgd.py"])

答案 2 :(得分：1)

问题在于反应堆无法重新启动。关于3个解决方案： 一种。搜寻程序 b。爬行者 C。子流程 我们可以使用CrawlerRunner和SubProcess，但是我们必须手动控制如何启动/停止反应堆。

我已经使用Flask（@ app.before_first_request）在任何请求之前注入逻辑来启动反应堆，

    @app.before_first_request
    def activate_job():
        def run_job():
            #time.sleep(0.5)
            try:
                if not reactor.running:
                    reactor.run()
            except:
                pass
        
        thread = Thread(target=run_job)
        thread.start()

然后，如果您想使用SubProcess：

    # how to pass parameters: https://stackoverflow.com/questions/15611605/how-to-pass-a-user-defined-argument-in-scrapy-spider
    def crawl_by_process(self):
        crawlSettings = {};
        subprocess.check_output(['scrapy', 'crawl', "demoSpider", '-a', 'cs='+json.dumps(crawlSettings)])

或者如果您想使用CrawlerProcess 

    # async, will return immediately and won't wait crawl finished
    def crawl(self):
        crawlSettings = {}

        configure_logging()

        s = get_project_settings()
        for a in inspect.getmembers(settings):
            if not a[0].startswith('_'):
                # Ignores methods
                if not inspect.ismethod(a[1]):
                    s.update({a[0]:a[1]})

        # if you want to use CrawlerRunner, when you want to integrate Scrapy to existing Twisted Application
        runner = CrawlerRunner(s)
        d = runner.crawl(demoSpider.DemoSpider, crawlSettings)
        d.addCallback(return_spider_output)
        return d
 
 def return_spider_output(output):
    """
    :param output: items scraped by CrawlerRunner
    :return: json with list of items
    """
    # this just turns items into dictionaries
    # you may want to use Scrapy JSON serializer here
    return json.dumps([dict(item) for item in output])

这是我的博客文章，解释上述逻辑： https://dingyuliang.me/scrapy-how-to-build-scrapy-with-flask-rest-api-2/

答案 3 :(得分：0)

至少还有一种方法尚未使用，即使用crochet库。为了演示，我们创建了一个最小的flask应用程序，该应用程序返回JSON输出以及基本example spider的修改版本。

flask_app.py：

import crochet
crochet.setup()  # initialize crochet before further imports

from flask import Flask, jsonify
from scrapy import signals
from scrapy.crawler import CrawlerRunner
from scrapy.signalmanager import dispatcher

from myproject.spiders import example


app = Flask(__name__)
output_data = []
crawl_runner = CrawlerRunner()
# crawl_runner = CrawlerRunner(get_project_settings()) if you want to apply settings.py


@app.route("/scrape")
def scrape():
    # run crawler in twisted reactor synchronously
    scrape_with_crochet()

    return jsonify(output_data)


@crochet.wait_for(timeout=60.0)
def scrape_with_crochet():
    # signal fires when single item is processed
    # and calls _crawler_result to append that item
    dispatcher.connect(_crawler_result, signal=signals.item_scraped)
    eventual = crawl_runner.crawl(
        example.ToScrapeSpiderXPath)
    return eventual  # returns a twisted.internet.defer.Deferred


def _crawler_result(item, response, spider):
    """
    We're using dict() to decode the items.
    Ideally this should be done using a proper export pipeline.
    """
    output_data.append(dict(item))


if __name__=='__main__':
    app.run('0.0.0.0', 8080)

spiders / example.py：

import scrapy


class MyItem(scrapy.Item):
    text = scrapy.Field()
    author = scrapy.Field()


class ToScrapeSpiderXPath(scrapy.Spider):
    name = 'toscrape-xpath'
    start_urls = [
        'http://quotes.toscrape.com/',
    ]

    def parse(self, response):
        for quote in response.xpath('//div[@class="quote"]'):
            return MyItem(
                text=quote.xpath('./span[@class="text"]/text()').extract_first(),
                author=quote.xpath('.//small[@class="author"]/text()').extract_first())

        next_page_url = response.xpath('//li[@class="next"]/a/@href').extract_first()
        if next_page_url is not None:
            return scrapy.Request(response.urljoin(next_page_url))

整个设置都是以同步方式完成的，这意味着/scrape在完成抓取过程之前不会返回任何内容。这是钩针编织文档中的一些其他信息：

  

设置：在设置过程中，Crochet会为您做很多事情。最重要的是，它在它管理的线程中运行Twisted的反应堆。

     

@wait_for：阻止对Twisted（...）的调用调用装饰函数时，代码不会在调用线程中运行，而是在反应堆线程中运行。
  该功能将阻塞，直到从Twisted线程中运行的代码获得结果为止。

此解决方案的灵感来自以下2篇文章：
Execute Scrapy spiders in a Flask web application
Get Scrapy crawler output/results in script file function

请注意，这是一种非常类似于原型的方法，例如output_data将在请求后保持其状态。如果您只是在寻找一种开始的方式，那就可以了。

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