HTTPDNS:How it works

Client triggers resolution

1. The application calls the HTTPDNS SDK resolution interface to initiate a domain name resolution request (such as www.aliyun.com).

2. The SDK queries the local cache on the client:

   • If cached results exist and have not expired, the IP list is returned.

   • If the cache is invalid or no record exists, the SDK initiates a recursive resolution request to the server.

SDK requests to the HTTPDNS server

1. The SDK calls the HTTP API to send a single domain name resolution request to the server.

2. The server performs iterative queries to authoritative DNS servers according to the standard DNS protocol.

3. The server returns the final recursive resolution results to the SDK.

SDK processes server response results

1. The SDK caches the latest IP list and manages the lifecycle based on TTL.

2. The SDK returns the IP list to the application based on the current network stack (and IP speed test sorting).