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Scrapy spider middleware to use Scrapinghub's Hub Crawl Frontier as a backend for URLs

Project description

https://travis-ci.org/scrapy-plugins/scrapy-hcf.svg?branch=master https://codecov.io/gh/scrapy-plugins/scrapy-hcf/branch/master/graph/badge.svg

This Scrapy spider middleware uses the HCF backend from Scrapinghub’s Scrapy Cloud service to retrieve the new urls to crawl and store back the links extracted.

Installation

Install scrapy-hcf using pip:

$ pip install scrapy-hcf

Configuration

To activate this middleware it needs to be added to the SPIDER_MIDDLEWARES dict, i.e:

SPIDER_MIDDLEWARES = {
    'scrapy_hcf.HcfMiddleware': 543,
}

And the following settings need to be defined:

HS_AUTH
Scrapy Cloud API key
HS_PROJECTID
Scrapy Cloud project ID (not needed if the spider is ran on dash)
HS_FRONTIER
Frontier name.
HS_CONSUME_FROM_SLOT
Slot from where the spider will read new URLs.

Note that HS_FRONTIER and HS_CONSUME_FROM_SLOT can be overriden from inside a spider using the spider attributes hs_frontier and hs_consume_from_slot respectively.

The following optional Scrapy settings can be defined:

HS_ENDPOINT
URL to the API endpoint, i.e: http://localhost:8003. The default value is provided by the python-hubstorage package.
HS_MAX_LINKS
Number of links to be read from the HCF, the default is 1000.
HS_START_JOB_ENABLED
Enable whether to start a new job when the spider finishes. The default is False
HS_START_JOB_ON_REASON
This is a list of closing reasons, if the spider ends with any of these reasons a new job will be started for the same slot. The default is ['finished']
HS_NUMBER_OF_SLOTS
This is the number of slots that the middleware will use to store the new links. The default is 8.

Usage

The following keys can be defined in a Scrapy Request meta in order to control the behavior of the HCF middleware:

'use_hcf'
If set to True the request will be stored in the HCF.
'hcf_params'

Dictionary of parameters to be stored in the HCF with the request fingerprint

'qdata'
data to be stored along with the fingerprint in the request queue
'fdata'
data to be stored along with the fingerprint in the fingerprint set
'p'
Priority - lower priority numbers are returned first. The default is 0

The value of 'qdata' parameter could be retrieved later using response.meta['hcf_params']['qdata'].

The spider can override the default slot assignation function by setting the spider slot_callback method to a function with the following signature:

def slot_callback(request):
    ...
    return slot

Project details


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