我在backend1 loadbalancer后面设置了12个后端节点（名为backend12到HAProxy）。如果我理解HAProxy默认模式它应该使用http持久连接 - 问题是在我的情况下，基于我使用netstat工具看到的内容似乎无法正常工作。
下面是针对netstat后面的单个后端节点执行简单loadtest执行期间HAProxy命令的片段（另一个设置为MAINT状态）。我网络中的负载均衡器IP是10.254.1.39
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 171 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED on (0,18/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 171 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED on (0,20/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED on (0,20/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 88 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED on (0,20/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58492 ESTABLISHED off (0.00/0/0)
tcp 0 170 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED on (0,19/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58492 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED on (0,21/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58492 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 171 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED on (0,20/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED on (0,19/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:58492 ESTABLISHED on (0,21/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 170 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED on (0,20/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58492 ESTABLISHED off (0.00/0/0)
tcp 0 170 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED on (0,18/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED on (0,21/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58492 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED on (0,22/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:58272 ESTABLISHED off (0.00/0/0)
tcp 0 170 10.254.1.12:9091 10.254.1.39:58188 ESTABLISHED on (0,18/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58424 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58492 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58620 ESTABLISHED off (0.00/0/0)
tcp 0 170 10.254.1.12:9091 10.254.1.39:58643 ESTABLISHED on (0,19/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:58333 ESTABLISHED off (0.00/0/0)
我可以看到，随着时间的推移，更多的连接被打开，但旧的连接被保留并被重用。同样的事情是，如果我将backend1添加到MAINT并仅启用backend2
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39458 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 171 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED on (0,21/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39458 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED on (0,19/0/0)
tcp 0 171 10.254.1.13:9091 10.254.1.39:39458 ESTABLISHED on (0,20/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.13:9091 10.254.1.39:39458 ESTABLISHED on (0,19/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39526 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39610 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39458 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39526 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:39610 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39307 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39671 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39374 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39458 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:39526 ESTABLISHED off (0.00/0/0)
当我将两个后端（以及更多）放到READY时，问题就出现了。
backend1的输出：
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:59570 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:59574 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:59709 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:59706 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:60209 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:60212 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:60212 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:60826 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:60813 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:60831 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:60833 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:33498 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:33502 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:33500 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:33504 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:33507 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:34042 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:34039 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:34032 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:34036 ESTABLISHED on (0,18/0/0)
tcp 0 170 10.254.1.12:9091 10.254.1.39:34036 ESTABLISHED on (0,18/0/0)
tcp 96 0 10.254.1.12:9091 10.254.1.39:34045 ESTABLISHED off (0.00/0/0)
ubuntu@backend1:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.12:9091 10.254.1.39:38181 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38150 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38167 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38163 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38179 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38170 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38130 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38172 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38139 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38176 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:35450 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38158 ESTABLISHED off (0.00/0/0)
tcp 0 171 10.254.1.12:9091 10.254.1.39:38137 ESTABLISHED on (0,20/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38177 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38144 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38125 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38144 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.12:9091 10.254.1.39:38125 ESTABLISHED off (0.00/0/0)
和backend2
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:52464 ESTABLISHED off (0.00/0/0)
tcp 0 170 10.254.1.13:9091 10.254.1.39:52466 ESTABLISHED on (0,20/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:52628 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:52631 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:53127 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:53138 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:53137 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:53134 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:53819 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:53828 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:53826 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:53821 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 170 10.254.1.13:9091 10.254.1.39:54736 ESTABLISHED on (0,18/0/0)
tcp 0 171 10.254.1.13:9091 10.254.1.39:54728 ESTABLISHED on (0,18/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:54711 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:54738 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 170 10.254.1.13:9091 10.254.1.39:55342 ESTABLISHED on (0,18/0/0)
tcp 0 171 10.254.1.13:9091 10.254.1.39:55344 ESTABLISHED on (0,20/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:55340 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:55339 ESTABLISHED off (0.00/0/0)
ubuntu@backend2:~$ netstat -tao | grep 39:
tcp 0 0 10.254.1.13:9091 10.254.1.39:59507 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59502 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59489 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59491 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59471 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59497 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59493 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59509 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59457 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59479 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59511 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59470 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59505 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59465 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59488 ESTABLISHED off (0.00/0/0)
tcp 0 0 10.254.1.13:9091 10.254.1.39:59513 ESTABLISHED off (0.00/0/0)
查看负载均衡器端（10.254.1.39）上的端口号，它们正在更改，这意味着连接已关闭并再次重新打开。问题是 - 为什么？我假设如果在单节点情况下重用连接，我的后端服务器（spray-can：http://spray.io/）能够使用http持久连接。
这是我的HAProxy配置：
global
log 127.0.0.1 local0
log 127.0.0.1 local1 notice
#log loghost local0 info
maxconn 4096
#chroot /usr/share/haproxy
user haproxy
group haproxy
daemon
#debug
#quiet
defaults
log global
mode http
option httplog
option dontlognull
retries 3
option redispatch
maxconn 4096
contimeout 5000
clitimeout 50000
srvtimeout 50000
frontend lb
bind *:8080
acl read_model_acl path_beg /check
use_backend read_models if read_model_acl
backend read_models
balance roundrobin
server read-model1 10.254.1.12:9091 check
server read-model2 10.254.1.13:9091 check
#more servers