http upstream keepalives

[Davide D'Amico]

> ------------------------------
>
> Message: 10
> Date: Mon, 14 May 2012 19:57:00 +0100
> From: Francis Daly <francis at daoine.org>
> To: nginx at nginx.org
> Subject: Re: http upstream keepalives
> Message-ID: <20120514185700.GJ457 at craic.sysops.org>
> Content-Type: text/plain; charset=us-ascii
>
> On Mon, May 14, 2012 at 07:32:18PM +0200, Davide D'Amico wrote:
>
> Hi there,
>
>> Hi, I'm reading here:
>> 
>> http://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive
>>
>> so I've tried:
>>
>> server {
>
>>   proxy_set_header        Host $host;
>>   proxy_set_header        X-Real-IP $remote_addr;
>>   proxy_set_header        X-Forwarded-For 
>> $proxy_add_x_forwarded_for;
>
>>   location / {
>>     proxy_http_version 1.1;
>>     proxy_set_header Connection "";
>
> That proxy_set_header directive means that any at an enclosing scope
> are not relevant in this location{}.
>
>>     proxy_pass http://172.16.7.9:2323;
>>   }
>> }
>>
>> On 172.16.7.9 I launched:
>>
>> > nc -4 -l 172.16.7.9 2323
>>
>> And so I saw:
>> GET / HTTP/1.1
>> Host: 172.16.7.9:2323
>> User-Agent: Wget/1.12 (darwin10.5.0)
>> Accept: */*
>>
>>
>> As you can see the Host header is wrong so I tested this vhost:
>
> No, the Host: header is what you configured it to be.
>
> As your next example also shows.
>
>> So I think that a little modification to documentation could be a 
>> good
>> idea :)
>
> The documentation you link to looks correct to me.
>
> (As I read it, it says "Last-Modified: Mon, 23 Apr 2012 13:32:31 
> GMT".)
>
> It includes "..." where you include specific directives. It turns out 
> that
> the specific directives you include don't do what you expected them 
> to.
>
> So: what documentation update could have avoided your confusion, or
> adjusted your expectations to match what nginx actually does?
>
> Note that this is unrelated to the "keepalive" directive; it is 
> arguably
> related to the proxy_set_header directive; but it is probably more
> generally related to directive inheritance in nginx.
>
> Some directives don't inherit at all -- so if you want it to apply in
> a location{}, you must set it in that location.
>
> Some directives do inherit from http > server > location -- so to see
> whether it applies in a location{}, you may have to check enclosing
> scopes too.
>
> Some (few) directives are "paired", and will affect the inheritance 
> of a
> different directive -- so to see whether it applies in a location{}, 
> you
> have to check its partner directive too, possibly in enclosing 
> scopes.
>
> But for all(?) directives that do inherit, inheritance is by 
> replacement,
> not addition.
>
> Where would you have looked to find notes like the above? Perhaps if 
> a
> suitable place can be identified, a corrected version could be put 
> there.
>

Indeed you are right but I read 
(http://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive):

For HTTP, the proxy_http_version directive should be set to “1.1” and 
the “Connection” header field should be cleared:

upstream http_backend {
     server 127.0.0.1:8080;

     keepalive 16;
}

server {
     ...

     location /http/ {
         proxy_pass http://http_backend;
         proxy_http_version 1.1;
         proxy_set_header Connection "";
         ...
     }
}

So i was thinking that in this scenario all other proxy_set_header 
options were inherited from the server stanza.
Clarify this point could help. That's all.

Thanks for your answers.