upstream server and ip hash

[Ruslan Ermilov]

On Sun, Aug 05, 2012 at 10:10:39PM -0700, kvhdude wrote:
> Folks,
>   Can anyone help me out?
>   To clarify: I am just looking for confirmation as i add an upstream
> server, will hash change for existing users (these are using XMPP sessions
> so they will suffer disruption of service).

Yes, it will.  The hashing implemented by ip_hash is not consistent.

There's limited support for preserving hash values when a server in
an upstream goes down, in the form of the "down" parameter, please
see http://nginx.org/r/ip_hash for details.

Adding consistent hashing is planned in future versions of nginx.

> kvhdude wrote
> > 
> > Hi,
> > 
> > I need a clarification regarding ip_hash directive :
> > Would adding a new upstream server affect existing users that are bound to
> > some other servers?
> > I am trying to dynamically scale up the servers (using scalr) in EC2
> > setting.
> > 
> > I am guessing it won't, but i needed to be sure.