upstream host name or address

Maxim Dounin mdounin at
Mon Jun 20 01:39:58 MSD 2011


On Sun, Jun 19, 2011 at 07:26:58AM -0400, torajx wrote:

> hi,
> is it possible to find upstream host which serves as proxy for a
> connection;
> i know that $upstream_addr is the key ; but i need to set the address
> with set_proxy_headdr as host
> but $upstream_addr return address and port together
> upstream test
> {
> ip_hash;
> }
> location /
> {
> proxy_set_header Host $upstream_addr;  ---------> fail cause it set for
> example but i need
> proxy_pass http://test;
> }
> any suggestion ?

Request is created only once and you can't set different headers 
when working with different servers in upstream.  Servers in 
upstream block must accept identical requests.

(Moreover, $upstream_addr isn't an address of upstream server nginx is
talking to, but a list of servers nginx have talked to during 
handling of a request.  And usually it won't contain anything 
while creating request to upstream.)

If you really need different requests to different backend servers 
you'll have to use different proxy_pass'es for that (or use 
variables).  E.g. in 0.9.6+ you may do something like this:

    map $remote_addr $backend {
        default          "should not happen";

    location / {
        proxy_pass http://$backend;

(no need for proxy_set_header here, as $proxy_host will resolve to 
the backend's ip address and default "proxy_set_header Host 
$proxy_host;" will do what you want)

But note that recommended aproach is to actually configure 
identical backend hosts, not adapt requests for each one.

Maxim Dounin

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