scrapy相关：splash 实践

0.

1.参考

https://github.com/scrapy-plugins/scrapy-splash#configuration

以此为准

scrapy相关：splash安装 A javascript rendering service 渲染

1. 启动 Docker Quickstart Terminal
2. 使用 putty 连接如下ip，端口22，用户名/密码：docker/tcuser
3. 开启服务：
   1. 　　sudo docker run -p 5023:5023 -p 8050:8050 -p 8051:8051 scrapinghub/splash
4. 浏览器打开：http://192.168.99.100:8050/

docker is configured to use the default machine with IP 192.168.99.100
For help getting started, check out the docs at https://docs.docker.com

Start interactive shell

win7@win7-PC MINGW64 ~
$

2.实践

2.1新建项目后修改 settings.py

ROBOTSTXT_OBEY 改为 False，同时添加如下内容：

'''https://github.com/scrapy-plugins/scrapy-splash#configuration'''
# 1.Add the Splash server address to settings.py of your Scrapy project like this:
SPLASH_URL = 'http://192.168.99.100:8050'

# 2.Enable the Splash middleware by adding it to DOWNLOADER_MIDDLEWARES in your settings.py file 
# and changing HttpCompressionMiddleware priority:
DOWNLOADER_MIDDLEWARES = {
    'scrapy_splash.SplashCookiesMiddleware': 723,
    'scrapy_splash.SplashMiddleware': 725,
    'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware': 810,
}
# Order 723 is just before HttpProxyMiddleware (750) in default scrapy settings.
# HttpCompressionMiddleware priority should be changed in order to allow advanced response processing; 
# see https://github.com/scrapy/scrapy/issues/1895 for details.

# 3.Enable SplashDeduplicateArgsMiddleware by adding it to SPIDER_MIDDLEWARES in your settings.py:
SPIDER_MIDDLEWARES = {
    'scrapy_splash.SplashDeduplicateArgsMiddleware': 100,
}
# This middleware is needed to support cache_args feature; 
# it allows to save disk space by not storing duplicate Splash arguments multiple times in a disk request queue. 
# If Splash 2.1+ is used the middleware also allows to save network traffic by not sending these duplicate arguments to Splash server multiple times.

# 4.Set a custom DUPEFILTER_CLASS:
DUPEFILTER_CLASS = 'scrapy_splash.SplashAwareDupeFilter'

# 5.If you use Scrapy HTTP cache then a custom cache storage backend is required. 
# scrapy-splash provides a subclass of scrapy.contrib.httpcache.FilesystemCacheStorage:
HTTPCACHE_STORAGE = 'scrapy_splash.SplashAwareFSCacheStorage'
# If you use other cache storage then it is necesary to subclass it 
# and replace all scrapy.util.request.request_fingerprint calls with scrapy_splash.splash_request_fingerprint.

# Note
# Steps (4) and (5) are necessary because Scrapy doesn't provide a way to override request fingerprints calculation algorithm globally; this could change in future.
# There are also some additional options available. Put them into your settings.py if you want to change the defaults:
# SPLASH_COOKIES_DEBUG is False by default. Set to True to enable debugging cookies in the SplashCookiesMiddleware. This option is similar to COOKIES_DEBUG for the built-in scarpy cookies middleware: it logs sent and received cookies for all requests.
# SPLASH_LOG_400 is True by default - it instructs to log all 400 errors from Splash. They are important because they show errors occurred when executing the Splash script. Set it to False to disable this logging.
# SPLASH_SLOT_POLICY is scrapy_splash.SlotPolicy.PER_DOMAIN by default. It specifies how concurrency & politeness are maintained for Splash requests, and specify the default value for slot_policy argument for SplashRequest, which is described below.

2.2 编写基本 spider

# -*- coding: utf-8 -*-
import scrapy
from scrapy_splash import SplashRequest
from scrapy.shell import inspect_response
import base64
from PIL import Image
from io import BytesIO


class CnblogsSpider(scrapy.Spider):
    name = 'cnblogs'
    allowed_domains = ['cnblogs.com']
    start_urls = ['https://www.cnblogs.com/']
    
    def start_requests(self):
        for url in self.start_urls:
            yield SplashRequest(url, self.parse, args={'wait': 0.5})    

    def parse(self, response):
        inspect_response(response, self)  ########################

调试 view(response) 是个txt。。。另存为 html 使用浏览器浏览即可。

2.3 编写截图 spider

同时参考 https://stackoverflow.com/questions/45172260/scrapy-splash-screenshots

    def start_requests(self):
        splash_args = {
            'html': 1,
            'png': 1,
            #'width': 1024, #默认1027*768,4:3
            #'render_all': 1, #长图截屏，不提供则是第一屏，需要同时提供 wait,否则报错
            #'wait': 0.5,
            
        }
             
        for url in self.start_urls:
            yield SplashRequest(url, self.parse, endpoint='render.json', args=splash_args)

http://splash.readthedocs.io/en/latest/api.html?highlight=wait#render-png

render_all=1 requires non-zero wait parameter. This is an unfortunate restriction, but it seems that this is the only way to make rendering work reliably with render_all=1.

https://github.com/scrapy-plugins/scrapy-splash#responses

Responses

scrapy-splash returns Response subclasses for Splash requests:

• SplashResponse is returned for binary Splash responses - e.g. for /render.png responses;
• SplashTextResponse is returned when the result is text - e.g. for /render.html responses;
• SplashJsonResponse is returned when the result is a JSON object - e.g. for /render.json responses or /execute responses when script returns a Lua table.

SplashJsonResponse provide extra features:

• response.data attribute contains response data decoded from JSON; you can access it like response.data['html'].

show 另存文件

    def parse(self, response):
        # In [6]: response.data.keys()
        # Out[6]: [u'title', u'url', u'geometry', u'html', u'png', u'requestedUrl']        
    
        imgdata = base64.b64decode(response.data['png'])
        img = Image.open(BytesIO(imgdata))
        img.show()
        filename = 'some_image.png'
        with open(filename, 'wb') as f:
            f.write(imgdata)        
        inspect_response(response, self)  ########################

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