Making new server parameter inside upstream block

Дмитрий Шалашов skaurus at
Thu Feb 12 20:11:00 UTC 2015

> Just use names in the configuration.

You mean local DNS?

Best regards,
Dmitriy Shalashov

2015-02-12 17:53 GMT+03:00 Maxim Dounin <mdounin at>:

> Hello!
> On Thu, Feb 12, 2015 at 05:19:46PM +0300, Дмитрий Шалашов wrote:
> > Ok, thanks.
> >
> > Can you imagine any other viable way to pass some information to each
> > server? It doesn't need to change between server restarts.
> > I may use a distinct variable for each of them but this seems ugly and
> > error-prone...
> You may want to rethink what you are trying to do.  In this
> particular case the whole task seems to be unneeded, see below.
> > In case you are curious why would I need this, let me explain.
> > Upstream directive support "hash consistent" method and in that case it
> > uses `ketama` algorithm. That means that each server assigned a key and
> > depending on its value (actually hash of that value) each server mapped
> to
> > a multiple points on the ketama ring. So far so good.
> > Documentation says that keys distribution is compatible with Perl
> > Cache::Memcached::Fast module. And that means that key for each server is
> > "$ip\0$port" (or something else for unix sockets, doesn't matter).
> > This means that if server ip changes, position of server points on ketama
> > ring will change too. Now, I'm balancing via this upstream not memcacheds
> > or other rather ephemeral storages but files. Each server in the upstream
> > have a hundreds of gigabytes of files. And I would like to avoid
> > rebalancing all these files in case of public ip changes.
> > So my idea was to pass a key for each server via parameter. Actually, to
> > preserve compatibility with current keys, I would pass a base64 of
> > "$ip\0$port" value, decode it during module init and happily use it for
> > ketama purposes. And be safe against servers redeployments.
> Just use names in the configuration.  Both Cache::Memcached::Fast
> and nginx will happily use names of servers and will derive
> Ketama points from names, not IP-addresses.  That is, key
> distribution will stay the same as long as you don't change names
> configured, regardless of IP-addresses.
> --
> Maxim Dounin
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