在scrapy中使用phantomJS实现异步爬取

最新推荐文章于 2023-11-26 08:00:00 发布

原创最新推荐文章于 2023-11-26 08:00:00 发布 · 2.8k 阅读

CC 4.0 BY-SA版权

本文介绍如何在Scrapy中利用PhantomJS进行异步爬取网页内容。通过重写Scrapy的下载器并集成Selenium，实现对网页的异步处理，确保在高并发情况下仍能有效抓取数据。示例代码展示了具体实现方法，包括设置下载器、启动PhantomJS实例、切换窗口以及处理响应。

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使用selenium能够非常方便的获取网页的ajax内容，并且能够模拟用户点击和输入文本等诸多操作，这在使用scrapy爬取网页的过程中非常有用。网上将selenium集成到scrapy的文章很多，但是很少有能够实现异步爬取的，下面这段代码就重写了scrapy的downloader，同时实现了selenium的集成以及异步。使用时需要PhantomJSDownloadHandler添加到配置文件的DOWNLOADER中。

# encoding: utf-8
from __future__ import unicode_literals

from scrapy import signals
from scrapy.signalmanager import SignalManager
from scrapy.responsetypes import responsetypes
from scrapy.xlib.pydispatch import dispatcher
from selenium import webdriver
from six.moves import queue
from twisted.internet import defer, threads
from twisted.python.failure import Failure


class PhantomJSDownloadHandler(object):

    def __init__(self, settings):
        self.options = settings.get('PHANTOMJS_OPTIONS', {})

        max_run = settings.get('PHANTOMJS_MAXRUN', 10)
        self.sem = defer.DeferredSemaphore(max_run)
        self.queue = queue.LifoQueue(max_run)

        SignalManager(dispatcher.Any).connect(self._close, signal=signals.spider_closed)

    def download_request(self, request, spider):
        """use semaphore to guard a phantomjs pool"""
        return self.sem.run(self._wait_request, request, spider)

    def _wait_request(self, request, spider):
        try:
            driver = self.queue.get_nowait()
        except queue.Empty:
            driver = webdriver.PhantomJS(**self.options)

        driver.get(request.url)
        # ghostdriver won't response when switch window until page is loaded
        dfd = threads.deferToThread(lambda: driver.switch_to.window(driver.current_window_handle))
        dfd.addCallback(self._response, driver, spider)
        return dfd

    def _response(self, _, driver, spider):
        body = driver.execute_script("return document.documentElement.innerHTML")
        if body.startswith("<head></head>"):  # cannot access response header in Selenium
            body = driver.execute_script("return document.documentElement.textContent")
        url = driver.current_url
        respcls = responsetypes.from_args(url=url, body=body[:100].encode('utf8'))
        resp = respcls(url=url, body=body, encoding="utf-8")

        response_failed = getattr(spider, "response_failed", None)
        if response_failed and callable(response_failed) and response_failed(resp, driver):
            driver.close()
            return defer.fail(Failure())
        else:
            self.queue.put(driver)
            return defer.succeed(resp)

    def _close(self):
        while not self.queue.empty():
            driver = self.queue.get_nowait()
            driver.close()