Scrapy Middleware Development Handbook: Customizing the Agent Scheduler Module

Hands-on with a smart faucet for Scrapy

Crawler brothers should have encountered the site blocked IP embarrassment, right? It's like when the water suddenly stops running in your house, so you can't do anything. At this time, if you can install a smart faucet (proxy IP pool), at any time to switch the water source, that is really cool! Today let's talk about how to install a customized faucet for Scrapy as a water pump.

Basic Plumber Operation

First understand Scrapy middleware is what the stuff. Simply put, it's a mechanism to add plug-ins to the crawler, like adding a filter to a water pipe. Proxy middleware is specifically responsible for changing the ordinary water pipe (local IP) into a variety of water sources (proxy IP).

Three valves that must be mastered:

• process_request: preparations before catching water
• process_response: check if water quality is acceptable
• process_exception: Emergency response in case of water leakage

Dynamic water management systems

Here's a pitfall to watch out for:Don't write off the IP pool as a stagnant pondThis is the first time I've seen this. Many newbies directly write the IP list to death in the code, the result is to use the use of all become stinky gutter. We recommend using ipipgo's dynamic IP pool service, their API interface can get fresh water in real time.

Intelligent water quality testing module

It's important to have a tester for each water source. Suggest adding a validation logic to process_response:

if response.status ! = 200.
    ipipgo.mark_bad_ip(current_proxy) mark bad ip
    return new_request Re-initiate the request

One good thing about ipipgo's package.Automatic recovery of invalid IPsThe first step is to write a maintenance script for the IP address of the IP address. The actual test with their API to replace the invalid IP, the success rate can be 99.2%.

Water flow scheduling black technology

Want to catch faster and steadier? Try these tawdry maneuvers:

• Geotargeting: with ipipgoCity-level positioning IPBreaking through regional constraints
• Protocol adaptation: according to the type of site to choose HTTP/HTIPSOCKS5 proxy
• Concurrency control: don't let too much water pressure burst the pipes (control the number of concurrencies)

A practical guide to avoiding the pit

Three common mistakes newbies make:

1. No timeout → Plumbing blocked the whole program.
2. Forget about the retry mechanism → occasional water outage and a total meltdown
3. IP switching too often → recognized as a robot

Remember to open them if you use ipipgo.Intelligent switching modeThe system will automatically match the best switching frequency. Tested with this function, the probability of IP blocking can be reduced to more than 70%.

Frequently Asked Questions QA

Q: What should I do if the proxy fails when I use it?
A: It is recommended to use ipipgo's auto-detection package, they will actively push the replacement IP 5 minutes before the IP failure

Q: What if I want to catch domestic and foreign websites at the same time?
A: In the middleware add geographical judgment logic, domestic station with ipipgo's BGP line, foreign station with their overseas line (note not!)

Q: Crawling like a snail?
A: Check if it's not open ipipgo'shigh speed channelThis has to be turned on separately in the console, and can speed up 3-5 times

Finally, remind the guys that middleware debugging is a delicate task. It is recommended to start with ipipgo'sFree Trial PackageTesting (500 requests per day is enough), tuning through and then on the official environment. When I encountered a jam, their technical customer service response is quite fast, much better than some half a day do not return the message of the brand.