Writing a script that reads a page takes an hour. Keeping it running for six months without interruption takes something else.
Sites change and defend themselves. Fragile collection always ends up stopping. A few principles make the difference.
Spread the requests
Rotating proxies spread traffic across a pool of addresses that changes regularly. A single access point hammering a site is spotted within minutes. Fifty addresses calling occasionally, much less so.
Slow down
The instinct is to go fast. It is the most common mistake. A collector that spaces its requests stays under detection thresholds, and it does not weigh on the site being read.
A site's robots.txt file also states what its publisher wants automated. The specification runs to two pages and is worth the detour.
Get past defences cleanly
Captchas, browser fingerprints, automated-behaviour detection: these mechanisms have multiplied in recent years. Handling them takes the right tools and constant attention, because they change often.
Check what comes out
Serious collection checks its own results. Empty fields, inconsistent formats, duplicates, impossible values. A hundred thousand clean rows beat three million unusable ones.
Repair quickly
A target site changes its structure and the extractor has to follow. That part of the work never stops. We listed the five most common failures and how to catch them before they cost anything.