[erlang-questions] Distributed erlang problem

[Chandru]

On 19/01/2008, Serge Aleynikov <saleyn@REDACTED> wrote:
>
> When you are starting db1@REDACTED{1,2}-rep are you binding distributed
> Erlang to the "rep" interface's IP address or using the default
> (0.0.0.0)?


I'm using the default.

A work around could be to use a
> separate gen_tcp (udp?) server listening on the "oam" interface and roll
> out a custom protocol so that would detect incoming connection requests
> (that are not based on Erlang's distribution), and cause
> db1@REDACTED{1,2}-rep nodes to initiate connections to OMC.


Or I can have an application on the DB nodes which ping the OMC node every
minute or so. Which seems a bit of a bodge but the only real solution I have
at the moment.

If you are binding the "rep" nodes to 0.0.0.0 then there shouldn't be
> any issue connecting from OMC unless there's a firewall restriction.


Well - there is an issue. This is because on the OMC node, host1-rep is
resolving to an IP address to which routing doesn't exist from the OMC (and
I can't get it added). The Security team won't allow this connectivity.

But is there a reason why the node name should have the hostname in it?
Can't we have an erlang node on a machine registering with any arbitrary
name in epmd? There could be kernel configuration on other nodes which can
specify the host for each node name. This will have the added benefit that
an mnesia database backup can easily be ported across various sets of nodes
without having to change the name of the nodes in the backup file (which is
a bit of a hack).

Thanks for your help.

cheers,
Chandru

Chandru wrote:
> > I am having a hard time figuring out how to get a few nodes to talk to
> each
> > other within certain rules. See figure below. Each box is a separate
> > physical server. The small boxes inside each big box are LAN cards.
> >
> >   +------------------+        +------------------+
> >   |               +--+        +--+               |
> >   | db1@REDACTED |  |........|  | db1@REDACTED |
> >   |               +--+        +--+               |
> >   |    +-oam--+      |        |       +-oam-+    |
> >   +----+--+---+------+        +-------+--+--+----+
> >           |                              |
> >           |                              |
> >           |                              |
> >           |                              |
> >           |      +-------------------+   |
> >           |      |                   |   |
> >           |      |                   |   |
> >           +------+       OMC         ....|
> >                  |                   |
> >                  |                   |
> >                  +-------------------+
> >
> >
> > I've got two database nodes on two hosts, each of which have two LAN
> cards.
> > One set of LAN cards are called the replication interfaces; they connect
> via
> > a special LAN which is very low latency and high bandwidth. This is used
> for
> > mnesia replication. To enable this, I start the DB nodes with the -sname
> > parameter set to 'db1@REDACTED'.
> >
> > Now there is a separate OMC node which should talk to the DB nodes via
> > distributed erlang on another set of interfaces. The problem is that the
> > 'host1-rep' interface is not reachable from the OMC host (due to
> security
> > issues). Only the 'host1-oam' interface is reachable. But, on the OMC
> node,
> > 'db1@REDACTED' is an unknown node.
> >
> > It seems that I need a feature where an erlang node on a machine can be
> > reached via multiple  names, such as 'db1@REDACTED', 'db1@REDACTED', '
> > db1@REDACTED, but I doubt this capability exists.
> >
> > Any suggestions? Anyone else had similar issues to deal with?
> >
> > regards,
> > Chandru
> >
> >
> >
>
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > erlang-questions mailing list
> > erlang-questions@REDACTED
> > http://www.erlang.org/mailman/listinfo/erlang-questions
>
>
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