Is this proxy setup realizable?

[Igor Sysoev]

On Wed, Aug 20, 2008 at 01:18:05AM +0200, Samuel Vogel wrote:

> Igor Sysoev schrieb:
> >On Tue, Aug 19, 2008 at 01:05:33AM +0200, Samuel Vogel wrote:
> >  
> >>I am planning on using nginx to be a reverse proxy infront of more than 
> >>ten real servers, each containing 10 virtual machines. These virtual 
> >>machines all contain the same setup lamp setup hosting about a 100 
> >>users/domains each.
> >>This means as a total we have about 10.000 domains. As we provide low 
> >>cost shared hosting on low cost servers, we can not switch the ip of a 
> >>virtual machine between servers. So when we migrate a VM to a different 
> >>physical server because of load reasons, it's IP changes as well.
> >>
> >>This is why we would like to use nginx infront as a reverse proxy. It 
> >>would then always know the corresponding IP for a virtual machine and 
> >>reroute the requests.
> >>
> >>With my current knowledge of nginx I would setup a virtual host for 
> >>every VM we have and add all the domains it contains into the 
> >>server_name variable. This would mean 100 virtual host with very long 
> >>server_names, each containing 100 domains.
> >>
> >>Additionally I would like to use the reverse proxy setup to sanitize the 
> >>requests, protect the VMs from dos attacks and if a VM goes down route 
> >>all requests to this VM to a static file like "we'll be back soon".
> >>
> >>My question is, would this configuration be maintainable with nginx? Can 
> >>it cope with long server_names and a rather strange setup like this? Or 
> >>will it degrade my performance too much?
> >>    
> >
> >nginx searchs server names via hash, so it will be quick opration.
> >nginx does primitive only sanitize.
> >As to "we'll be back soon", you need to use
> >
> >     error_page  502 504  /back.html;
> >  
> 
> Great! So even more than 10.000 domains would not matter and there is no 
> size limit to server_name?

No limit, however, you should increase server_names_hash_max_size
and, probably, server_names_hash_bucket_size. nginx will say by itself.
First you should increase server_names_hash_max_sizeand only.

A large number of server_name may cause reconfiguraiton delay as nginx
finds the best hash size, but in run-time the will no delay.

> As for the "we'll be back soon" page, I thought I'd put the real server 
> (VM) and a server only containing this error page into an upstream 
> section and mark the error page server as backup.
> But if the 502 and 504 errors achieve the same effect, this makes things 
> easier!

However, you still need to add

   location = /we_ll_be_back_soon.html {
       root  /path/to/thepage;
   }

in every server. The

      error_page  502 504  /we_ll_be_back_soon.html;

can be set on http level.


-- 
Igor Sysoev
http://sysoev.ru/en/