如何在haproxy中启用keep-alive？

Question

这是我的 haproxy.conf (haproxy 1.7.9)

global
    log             127.0.0.1 local0
defaults
    retries 3
    option redispatch
    timeout client  30s
    timeout connect 30s
    timeout server  30s
    option http-keep-alive
    http-reuse always

frontend web1
    bind *:8080
    option http-keep-alive
    mode http
    default_backend app1
backend app1
    balance     roundrobin
    option http-keep-alive
    mode http
    server a2 192.168.56.150:8000

源服务器的卷曲结果：

$ curl -vv http://192.168.56.150:8000/test --keepalive-time 700
* About to connect() to 192.168.56.150 port 8000 (#0)
*   Trying 192.168.56.150...
* Connected to 192.168.56.150 (192.168.56.150) port 8000 (#0)
> GET /test HTTP/1.1
> User-Agent: curl/7.29.0
> Host: 192.168.56.150:8000
> Accept: */*
> 
< HTTP/1.1 200 OK 
< Etag: 720-6-59eeda80
< Content-Type: application/octet-stream
< Content-Length: 6
< Last-Modified: Tue, 24 Oct 2017 06:15:28 GMT
< Server: WEBrick/1.3.1 (Ruby/2.0.0/2015-12-16)
< Date: Fri, 27 Oct 2017 02:38:14 GMT
< Connection: Keep-Alive
< 
tests
* Connection #0 to host 192.168.56.150 left intact

haproxy 服务器的 curl 结果

$ curl -vv http://192.168.56.150:8080/test --keepalive-time 700
* About to connect() to 192.168.56.150 port 8080 (#0)
*   Trying 192.168.56.150...
* Connected to 192.168.56.150 (192.168.56.150) port 8080 (#0)
> GET /test HTTP/1.1
> User-Agent: curl/7.29.0
> Host: 192.168.56.150:8080
> Accept: */*
> 
< HTTP/1.1 200 OK 
< Etag: 720-6-59eeda80
< Content-Type: application/octet-stream
< Content-Length: 6
< Last-Modified: Tue, 24 Oct 2017 06:15:28 GMT
< Server: WEBrick/1.3.1 (Ruby/2.0.0/2015-12-16)
< Date: Fri, 27 Oct 2017 02:38:05 GMT
< 
tests
* Connection #0 to host 192.168.56.150 left intact

并且我通过 tcpdump 确认从 origin 到 haproxy

的响应中有 Connection: Keep-Alive

如你所见，haproxy response 中没有Connection: Keep-Alive，请问如何让haproxy keep-alive？？

Answer 1

HTTP 1.1 默认在 keep-alive 模式下运行，请参阅 RFC7230。因此，您无需明确设置 Connection header 即可使用持久连接（keep-alive 模式）。
只有在使用 HTTP 1.0 时才需要连接 header，因为它被设计为在每次请求后关闭连接。

因此，要验证 HAProxy 是否在 Keep-alive 模式下运行，您需要使用 curl 发送多个 HTTP 请求（而不是一个），并检查是否只有一个连接建立和使用。
serverfault post 展示了如何做到这一点。（注意 "Connecting to .." 和 "Closing connection" 行）

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