TL;DR
- Batch scraping thousands of URLs is a queue-management problem before it is an HTTP problem.
- Use bounded concurrency, per-request timeouts, retries with jitter, checkpoints, and an idempotent result key.
asyncioandaiohttpwork well for simple public pages; browser rendering or site discovery should move to a crawl service.- Nstdata Crawl is a better fit when the batch needs rendered pages, page artifacts, or controlled site-level collection rather than raw fetches.
Why large URL batches fail
Start with Nstdata Crawl when collection needs rendering or task state.
A batch scraper fails when submission rate, target-site limits, retries, and result storage are treated as one loop. A thousand URLs can produce duplicate writes, retry storms, open connections, and no reliable way to resume after a worker or process stops. Start with Nstdata Crawl when the batch is a crawl task rather than a list of simple HTTP requests.
The first design decision is the record identity. Use a canonical URL plus a fetch-configuration hash, not the position in an input file. Record queued, running, succeeded, failed, and dead_letter states, with the last error and attempt count. This makes a partial run repairable.
An asynchronous design that stays bounded
The safest pattern is a producer, a semaphore-limited worker pool, and a durable result sink. aiohttp documents the ClientSession pattern for asynchronous HTTP requests; the is the right reference for session lifecycle and timeouts.
