scrapyjs 0.2

JavaScript support for Scrapy using Splash

This library provides Scrapy and JavaScript integration using Splash. The license is BSD 3-clause.

Installation

Install ScrapyJS using pip:

$ pip install scrapyjs

ScrapyJS uses Splash HTTP API, so you also need a Splash instance. Usually to install & run Splash, something like this is enough:

$ docker run -p 8050:8050 scrapinghub/splash

Check Splash install docs for more info.

Configuration

1. Add the Splash server address to settings.py of your Scrapy project like this:

   SPLASH_URL = 'http://192.168.59.103:8050'

2. Enable the Splash middleware by adding it to DOWNLOADER_MIDDLEWARES in your settings.py file:

   DOWNLOADER_MIDDLEWARES = {
       'scrapyjs.SplashMiddleware': 725,
   }

Note

Order 725 is just before HttpProxyMiddleware (750) in default scrapy settings.

3. Set a custom DUPEFILTER_CLASS:

   DUPEFILTER_CLASS = 'scrapyjs.SplashAwareDupeFilter'

4. If you use Scrapy HTTP cache then a custom cache storage backend is required. ScrapyJS provides a subclass of scrapy.contrib.httpcache.FilesystemCacheStorage:

   HTTPCACHE_STORAGE = 'scrapyjs.SplashAwareFSCacheStorage'

   If you use other cache storage then it is necesary to subclass it and replace all scrapy.util.request.request_fingerprint calls with scrapyjs.splash_request_fingerprint.

Note

Steps (3) and (4) are necessary because Scrapy doesn’t provide a way to override request fingerprints calculation algorithm globally; this could change in future.

Usage

To render the requests with Splash, use the 'splash' Request meta key:

yield Request(url, self.parse_result, meta={
    'splash': {
        'args': {
            # set rendering arguments here
            'html': 1,
            'png': 1,

            # 'url' is prefilled from request url
        },

        # optional parameters
        'endpoint': 'render.json',  # optional; default is render.json
        'splash_url': '<url>',      # overrides SPLASH_URL
        'slot_policy': scrapyjs.SlotPolicy.PER_DOMAIN,
    }
})

• meta['splash']['args'] contains arguments sent to Splash. ScrapyJS adds request.url to these arguments automatically.

  Note that by default Scrapy escapes URL fragments using AJAX escaping scheme. If you want to pass a URL with a fragment to Splash then set url in args dict manually.

• meta['splash']['endpoint'] is the Splash endpoint to use. By default render.json is used.

  See Splash HTTP API docs for a full list of available endpoints and parameters.

• meta['splash']['splash_url'] overrides the Splash URL set in settings.py.

• meta['splash']['slot_policy'] customize how concurrency & politeness are maintained for Splash requests.

  Currently there are 3 policies available:

  1. scrapyjs.SlotPolicy.PER_DOMAIN (default) - send Splash requests to downloader slots based on URL being rendered. It is useful if you want to maintain per-domain politeness & concurrency settings.

  2. scrapyjs.SlotPolicy.SINGLE_SLOT - send all Splash requests to a single downloader slot. It is useful if you want to throttle requests to Splash.

  3. scrapyjs.SlotPolicy.SCRAPY_DEFAULT - don’t do anything with slots. It is similar to SINGLE_SLOT policy, but can be different if you access other services on the same address as Splash.

Examples

Get HTML contents:

import scrapy

class MySpider(scrapy.Spider):
    start_urls = ["http://example.com", "http://example.com/foo"]

    def start_requests(self):
        for url in self.start_urls:
            yield scrapy.Request(url, self.parse, meta={
                'splash': {
                    'endpoint': 'render.html',
                    'args': {'wait': 0.5}
                }
            })

    def parse(self, response):
        # response.body is a result of render.html call; it
        # contains HTML processed by a browser.
        # ...

Get HTML contents and a screenshot:

import json
import base64
import scrapy

class MySpider(scrapy.Spider):

    # ...
        yield scrapy.Request(url, self.parse_result, meta={
            'splash': {
                'args': {
                    'html': 1,
                    'png': 1,
                    'width': 600,
                    'render_all': 1,
                }
            }
        })

    # ...
    def parse_result(self, response):
        data = json.loads(response.body_as_unicode())
        body = data['html']
        png_bytes = base64.b64decode(data['png'])
        # ...

Run a simple Splash Lua Script:

import json
import base64

class MySpider(scrapy.Spider):

    # ...
        script = """
        function main(splash)
            assert(splash:go(splash.args.url))
            return splash:evaljs("document.title")
        end
        """
        yield scrapy.Request(url, self.parse_result, meta={
            'splash': {
                'args': {'lua_source': script},
                'endpoint': 'execute',
            }
        })

    # ...
    def parse_response(self, response):
        doc_title = response.body_as_unicode()
        # ...

HTTP Basic Auth

If you need HTTP Basic Authentication to access Splash, use Scrapy’s HttpAuthMiddleware.

Why not use the Splash HTTP API directly?

The obvious alternative to ScrapyJS would be to send requests directly to the Splash HTTP API. Take a look at the example below and make sure to read the observations after it:

import json

import scrapy
from scrapy.http.headers import Headers

RENDER_HTML_URL = "http://127.0.0.1:8050/render.html"

class MySpider(scrapy.Spider):
    start_urls = ["http://example.com", "http://example.com/foo"]

    def start_requests(self):
        for url in self.start_urls:
            body = json.dumps({"url": url, "wait": 0.5})
            headers = Headers({'Content-Type': 'application/json'})
            yield scrapy.Request(RENDER_HTML_URL, self.parse, method="POST",
                                 body=body, headers=headers)

    def parse(self, response):
        # response.body is a result of render.html call; it
        # contains HTML processed by a browser.
        # ...

It works and is easy enough, but there are some issues that you should be aware of:

1. There is a bit of boilerplate.

2. As seen by Scrapy, we’re sending requests to RENDER_HTML_URL instead of the target URLs. It affects concurrency and politeness settings: CONCURRENT_REQUESTS_PER_DOMAIN, DOWNLOAD_DELAY, etc could behave in unexpected ways since delays and concurrency settings are no longer per-domain.

3. Some options depend on each other - for example, if you use timeout Splash option then you may want to set download_timeout scrapy.Request meta key as well.

ScrapyJS utlities allow to handle such edge cases and reduce the boilerplate.

Contributing

Source code and bug tracker are on github: https://github.com/scrapy-plugins/scrapy-splash

To run tests, install “tox” Python package and then run tox command from the source checkout.

Changes

0.2 (2016-03-26)

• Scrapy 1.0 and 1.1 support;

• Python 3 support;

• documentation improvements;

• project is moved to https://github.com/scrapy-plugins/scrapy-splash.

0.1.1 (2015-03-16)

Fixed fingerprint calculation for non-string meta values.

0.1 (2015-02-28)

Initial release