How do I set up concurrent scraping tasks without IP blocking?

To run concurrent scraping tasks without IP blocking, combine rotating proxies, per‑host concurrency limits, request throttling with jitter, and browser‑realistic fingerprints—then tune based on live block/error rates. zenrows

Setup blueprint

1. Use a large rotating proxy pool

   • Prefer residential/mobile proxies for tough sites; datacenter proxies are fine for open sites.
   • Rotate IPs per request for stateless bulk scraping; use sticky sessions (5–10 min) for login/stateful flows. zenrows

2. Limit concurrency per domain and per IP

   • Cap concurrent requests to the same hostname (often 2–10 depending on defenses).
   • Keep concurrent requests per single IP very low (usually 1–2); scale by adding more identities (IPs), not more threads per IP. zenrows

3. Throttle and add jitter

   • Add random delays between requests (e.g., 2–5s base with jitter) and respect Retry-After on 429/503.
   • Use exponential backoff with capped retries; pause the entire domain queue when you see repeated blocks. zenrows

4. Match browser fingerprints and headers

   • Use a browser‑realistic HTTP client (e.g., curl_cffi, tls-client) or headless browser for protected sites.
   • Keep headers, cookies, and request order consistent within a session; rotate user agents alongside IPs. simplynode

5. Monitor block signals and adapt

   • Track 403/429 rates, soft blocks (200 OK with missing content), and latency spikes.
   • If block rate rises, reduce concurrency and slow down immediately; consider switching proxy tier (e.g., to mobile) for that domain. eproxies

Practical defaults to start with

• Open/static sites: 1 residential IP per ~50–100 requests/min; 2–5 concurrent per domain; 2–5s delays.
• Moderately protected e‑commerce: 1 IP per ~20–50 requests/min; 1–2 concurrent per IP; sticky sessions of 5–10 min; jittered delays.
• Highly protected (Cloudflare/Akamai): per‑request rotation, 1 concurrent per identity, TLS/browser impersonation, slower ramps and frequent success‑rate checks. eproxies

If you share your targets and stack (language, proxy provider), I can suggest concrete concurrency and rotation settings. zenrows