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From Benjamin Black...@b3k.us>
Subject Re: Cassandra on AWS across Regions
Date Thu, 02 Sep 2010 16:58:11 GMT
On Thu, Sep 2, 2010 at 5:52 AM, Phil Stanhope <stanhope@gmail.com> wrote:
> Ben, can you elaborate on some infrastructure topology issues that would
> break this approach?
>

As noted, the naive approach results in nodes behind the same NAT
having to communicate with each other through that NAT rather than
directly.  You can different property files for property snitch on
different nodes, as that is directly encoding topology.  You could do
the same with /etc/hosts.  You could do the same with DNS.  The
problem is that in all these cases you have a different view of the
world depending on where you are.  Does this node have the right
information for connecting to local nodes and remote nodes?  Is it
failing to connect to some other node because of a hostname resolution
failure, or because it has the wrong topology information, or ...?

And this only assumes 1:1 NAT.  What is the solution for PAT (which is
quite common)?  It's a deep dark hole of edge cases.  I would rather
have a dead simple 80% solution than a 100% solution with dynamics I
can't understand.


b

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