[cvsnt] Accessing repository on disaster recovery server

[Michael Wojcik]

> From: cvsnt-bounces at cvsnt.org 
> [mailto:cvsnt-bounces at cvsnt.org] On Behalf Of Brian McGuiness
> Sent: Friday, 27 October, 2006 04:45
> 
> The DR server has a different name (and is on a different domain) to
the 
> original server - can we still just use DNS for redirecting it?

Yes, though having the two servers in different domains does complicate
things.

If they were in the same domain, the simplest approach would be to have
all the CVS clients refer to an alias, which could be transferred from
the primary to the secondary server.

For example, say the primary server is named "cvs-serv" and the
secondary (DR) server is named "cvs-dr".  Rather than using either of
those names in your CVS clients' root specifications, give cvs-serv an
alias (CNAME) of "cvs" and use that.  (Your clients would specify a root
along the lines of ":sspi:user at cvs:2401:/top".)

To switch to the DR server, you'd change your DNS configuration to
associate the "cvs" CNAME with the cvs-dr server.  Then, modulo
propagation delays, the clients would start going to the DR server.

For this to work with the machines in different domains, the client
machines will have to be configured with both domains in their resolver
searchlist, so that they'll ask DNS to resolve "cvs" in both the primary
and secondary domains.  Also, typically different domains have separate
configurations, in which case switching to the DR server would involve
updating and refreshing two DNS configurations, rather than just one.

Frankly, it would probably be easier to use a DR server architecture
that supports transparent hot-standby servers, so that the primary and
DR servers can use the same (fully-qualified) name.  Alternatively, you
could have a single proxy server that forwards CVS requests to either
the primary or the secondary server, depending on which is available.  I
don't know offhand of any existing CVSNT proxy, but at first glance it
seems pretty trivial to implement.  (I've proxied the CVSNT lockserver
for debugging purposes.)

-- 
Michael Wojcik
Principal Software Systems Developer, Micro Focus