[tarantool-patches] Re: [PATCH v2] iproto: introduce a proxy module.

[Konstantin Osipov]

* Vladimir Davydov <vdavydov.dev at gmail.com> [18/10/11 09:55]:
> On Tue, Oct 02, 2018 at 09:05:54PM +0300, Serge Petrenko wrote:
> > Since salt proxy sends to a client differs from the salt it recieves
> > from a remote instance, forwarding auth requests to establish non-guest
> > connections is a little bit tricky:
> > let hash1 = sha1(password),
> >     hash2 = sha1(hash1)
> > then upon auth proxy recieves such a string from the client:
> >     reply = xor(hash1, sha1(proxy_salt, hash2))
> > proxy has to send an auth request of such form to an instance:
> >     request = xor(hash1, sha1(instance_salt, hash2))
> > proxy fetches hash2 via a special message to tx thread (again, it is
> > accessible, since proxy is run on one of the cluster instances).
> > Then proxy computes hash1 = xor(reply, sha1(proxy_salt, hash2)) and
> > computes the request using hash1, hash2 and instance_salt.
> 
> So unless the user is fine with guest access (which is rather unlikely
> AFAIU), it doesn't make sense to run a proxy on a standalone instance,
> does it?
> 
> If so, may be we could simplify both configuration and the code by
> requiring a proxy to be a part of the replica set?

It's OK to simplify the patch now and only make it work within a
replica set. In future we will have replication groups, remember,
and this way we'll get a standalone proxy for free.

> I mean instead of netbox.listen(), we could add a knob to box.cfg, say
> box.cfg.proxy_enable = true|false. If this knob was set, the instance
> would automatically forward all incoming iproto requests to members of
> the replica set (including self). What do you think?

We need a new knob for two reasons:
- we need to be able to turn on listen port before box.cfg; it's
  albeit separate, a popular user request.
- we need backward compatibility. i.e. old listen should work the
  old way, to not surprise users
> 
> > Proxy may be configured like this:
> > ```
> > netbox = require("net.box")
> > netbox.listen(uri_to_listen, {cluster={
> > 	{uri=uri1, is_master=false},
> > 	{uri=uri2, is_master=true},
> > 	...
> > 	}})
> > ```
> 
> I don't like that the user has to explicitly configure which participant
> is rw and which is ro. How will it work when box.ctl.promote is finally
> implemented?

Can we please implement a proxy in which there is no
{cluster=} option? As we were discussing with Vlad, proxy should
be integrated with box.ctl.promote() and learn about ro/rw masters
from it.

-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov