DNS轮询

DNS轮询是一种简单的负载均衡技术,将多个具有不同[[ip-address|IP地址]]的[[a-record|A记录]]或[[aaaa-record|AAAA记录]]与单个主机名关联。[[recursive-dns|解析器]]依次循环这些地址,将传入连接分配到多台服务器。由于轮询依赖DNS级别的随机化而非会话感知,因此不提供健康检查或粘性会话;故障服务器在记录被手动更新或[[ttl|TTL]]过期之前将持续接收流量。更复杂的替代方案包括Anycast路由、GeoDNS和应用层负载均衡器。

示例

A website with three servers at 1.2.3.4, 1.2.3.5, and 1.2.3.6 can list all three as A records for www.example.com; successive DNS lookups return them in rotation, spreading traffic roughly evenly across all three servers.