timeout doesn't work （设置了timeout但是没有生效）

[noizz]

配置文件nginx.conf: upstream cluster {

    # simple round-robin
    server 172.51.171.12:9900;
    server 172.51.171.13:9900;

    check interval=10000 rise=1 fall=1 timeout=10;
    check_http_send "HEAD /mgr.do?acct=4141141 HTTP/1.0\r\n\r\n";
}

---

if curl http://172.51.171.12:9900/mgr.do?acct=4141141，it will spend more than 400ms.but this server is still alive. （如果访问 http://172.51.171.12:9900，实际需要600ms，但是查看状态，这个节点仍然是激活的）

curl http://localhost:8899/status?format=json

{"servers": { "total": 2, "generation": 1, "server": [ {"index": 0, "upstream": "cluster", "name": "172.51.171.12:9900", "status": "up", "rise": 6, "fall": 0, "type": "tcp", "port": 0}, {"index": 1, "upstream": "cluster", "name": "172.51.171.13:9900", "status": "up", "rise": 6, "fall": 0, "type": "tcp", "port": 0} ] }}

Question问题： any idea? 我这样设置对吗？应该怎么做？