Upstream: ngx_http_upstream_random module. The module implements random load-balancing algorithm with optional second choice. In the latter case, the best of two servers is chosen, accounting number of connections and server weight. Example: upstream u { random [two [least_conn]]; server 127.0.0.1:8080; server 127.0.0.1:8081; server 127.0.0.1:8082; server 127.0.0.1:8083; }