Root cause of neighbour=0 for large carriers (AS9002, AS3491, AS12956):
1. RIPE Stat asn-neighbours returns 5000+ entries for Tier-1 carriers,
exceeding the 30s timeout → fetchJSON returns null
2. null was cached in ripeStatCache for 15 minutes (the endpoint TTL)
3. All subsequent requests hit the null cache → perpetual 0 neighbours
Fixes:
- Never cache null results in ripeStatCache (only successful responses)
- Never persist null entries to disk cache
- Increase RIPE Stat timeout from 30s to 45s for prefix/neighbour queries
- Increase RIPE Stat semaphore from 10 to 15 concurrent requests
Verified: AS9002 up=146 down=2702, AS3491 up=90 down=710
8f51f32dc3