Recursive crawler design: dealing with paging and deep links

A recursive crawler why have to use proxy IP?

Engaged in data crawling know, paging links and deep pages are like Russian nesting dolls, a layer of a layer simply can not stop. At this time, if you use your own local IP hard just, minutes will be the target site black - especially the price data of e-commerce platforms, social media dynamics of these sensitive content.

To give a real example: one day I want to grab a certain treasure commodity comments, the first 5 pages are normal, to the 6th page suddenly returned 403 error. This is a typicalIPs are recognized as crawlersSymptoms. At this time if you use ipipgo's dynamic residential agent, every 3 pages to catch a new IP address, with random request header, the site can not tell whether it is a real person or a machine.

Second, the three axes of the paging crawl

Dealing with paging is like eating lasagna, you have to peel it off layer by layer:

1. Page pattern recognition:

Don't be silly to write a dead loop times! First manually point the website's pagination button, observe the change rule of the URL. There are three common forms:

Don't panic when it comes to hash parameters, use ipipgo'sJS Render Proxyservice, automatic execution of page JavaScript to generate dynamic parameters.

2. Termination condition setting:

Never get into a death spiral! Set up double insurance:

- Maximum page limit (e.g., grab up to 50 pages)
- Content duplication detection (stop when data duplication occurs on 3 consecutive pages)

III. The maze of deep links to crack the law

Deep links are like subway transfers, you have to find the right connection channel:

1. Use XPath or CSS selector to pinpoint the "detail page" link, note that some sites hide the link in thedata-hrefIn this custom property

2. when encountering asynchronously loaded links (e.g. scrolling loads), use ipipgo'sAPI proxyDirectly interfaces to the website, more than 10 times faster than an analog browser

3. To control the depth of recursion, it is recommended to useTree-structured storage::

Home Page
├─ List Page 1
│ ├─ Details Page A
│ └─ Details Page B
└─ List Page 2

IV. Proxy IP Practical Configuration Manual

Demonstrate how to implement smart rotation with ipipgo, using Python's requests library as an example:

import requests
from itertools import cycle

proxies = cycle([
    'http://user:pass@gateway.ipipgo.com:30001',
    'http://user:pass@gateway.ipipgo.com:30002'
])

def get_page(url): current_proxy = next(proxies)
    current_proxy = next(proxies)
    try: current_proxy = next(proxies)
        resp = requests.get(url, proxies={'http': current_proxy}, timeout=10)
        if 'CAPTCHA' in resp.text: Trigger a reverse crawl and immediately change IPs
            raise Exception('CAPTCHA triggered')
        return resp.text
    except.
        return get_page(url) recursive retry

Notice the use ofrecursive fault tolerance mechanism, combined with ipipgo's 99.9% availability guarantee, there are basically no cascading failures.

QA Frequently Asked Questions Demining

Q: What should I do if I always encounter Cloudflare validation?
A: Switch the proxy package of ipipgo to theResidential Proxy + Browser Fingerprinting Emulation, measured to bypass 90%'s 5-second shield.

Q: How to deal with memory overflow caused by recursive crawler?
A: Replace the recursive function with a generator, and release the memory immediately after each page is processed. Remember to turn on the ipipgo consoleFlow Compressionfunction to reduce the amount of data transfer.

Q: How do I determine whether I should use a static or dynamic proxy?
A: Look at the anti-crawl strength of the target site:
- General information site: static proxies are sufficient
- E-commerce finance class: must use dynamic agents
Contact ipipgo's tech support directly if you're not sure, they can recommend options based on the crawling scenario.

As a final rant, the most important thing about recursive crawlers is that theElegant degradationDesign. Last week a customer hard not to listen to advice, did not do exception handling directly run, the results triggered the target site's wind control mechanism. Later changed to ipipgoIntelligent Routing AgentThe data acquisition rate directly soared from 47% to 89%, so that the tool to choose the right one can really take ten years to go through the wrong path.