我有 nginx 上游的 redis 服务器（5 个服务器，每个服务器有 4 个 redis 实例），如下所示：
upstream redis_cluster {
server 10.0.1.8:6379 fail_timeout=0;
server 10.0.1.8:6380 fail_timeout=0;
server 10.0.1.8:6381 fail_timeout=0;
server 10.0.1.8:6382 fail_timeout=0;
server 10.0.1.6:6379 fail_timeout=0;
server 10.0.1.6:6380 fail_timeout=0;
server 10.0.1.6:6381 fail_timeout=0;
server 10.0.1.6:6382 fail_timeout=0;
...
keepalive 16;
}
在添加最后一台服务器（实际上是最后 4 个 redis 实例）之后，我注意到其中一些服务器出现了奇怪的连接：
9684 10.0.0.17:6379 TIME_WAIT
3 10.0.0.17:6380 ESTABLISHED
9677 10.0.0.17:6380 TIME_WAIT
9664 10.0.0.17:6381 TIME_WAIT
6 10.0.0.17:6382 ESTABLISHED
9660 10.0.0.17:6382 TIME_WAIT
4 10.0.1.3:6379 ESTABLISHED
1 10.0.1.3:6379 SYN_SENT
9671 10.0.1.3:6379 TIME_WAIT
3 10.0.1.3:6380 ESTABLISHED
9665 10.0.1.3:6380 TIME_WAIT
1 10.0.1.3:6381 ESTABLISHED
9661 10.0.1.3:6381 TIME_WAIT
5 10.0.1.3:6382 ESTABLISHED
9660 10.0.1.3:6382 TIME_WAIT
5 10.0.0.7:6379 ESTABLISHED
9653 10.0.0.7:6379 TIME_WAIT
4 10.0.0.7:6380 ESTABLISHED
9663 10.0.0.7:6380 TIME_WAIT
1 10.0.0.7:6381 ESTABLISHED
9664 10.0.0.7:6381 TIME_WAIT
7 10.0.0.7:6382 ESTABLISHED
9667 10.0.0.7:6382 TIME_WAIT
5 10.0.1.8:6379 ESTABLISHED
9673 10.0.1.8:6379 TIME_WAIT
2 10.0.1.8:6380 ESTABLISHED
9676 10.0.1.8:6380 TIME_WAIT
4 10.0.1.8:6381 ESTABLISHED
9665 10.0.1.8:6381 TIME_WAIT
3 10.0.1.8:6382 ESTABLISHED
注释掉最后一个服务器（最后 4 个上游条目）后，一切恢复正常：
4 10.0.0.10:6379 ESTABLISHED
4 10.0.0.10:6380 ESTABLISHED
4 10.0.0.10:6381 ESTABLISHED
1 10.0.0.10:6381 TIME_WAIT
4 10.0.0.10:6382 ESTABLISHED
4 10.0.1.3:6379 ESTABLISHED
4 10.0.1.3:6380 ESTABLISHED
4 10.0.1.3:6381 ESTABLISHED
4 10.0.1.3:6382 ESTABLISHED
4 10.0.0.7:6379 ESTABLISHED
4 10.0.0.7:6380 ESTABLISHED
4 10.0.0.7:6381 ESTABLISHED
4 10.0.0.7:6382 ESTABLISHED
4 10.0.1.8:6379 ESTABLISHED
4 10.0.1.8:6380 ESTABLISHED
4 10.0.1.8:6381 ESTABLISHED
4 10.0.1.8:6382 ESTABLISHED
造成这种情况的根本原因是什么？ 提前谢谢各位同志了。