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[LDM #SER-849220]: Request for adding new IPs to allowed LDM connection

Hi Gyorgyi,

re:
> If the order in ldmd.conf does not matter, then how do they decide which
> one is primary and which one is alternate?

This is an excellent question!

If one has redundant feed REQUESTs to two upstreams using _exactly_
the same extended regular expressions, then the connection that is
the fastest (as measured by how many products it receives compared
to the other feed) will be promoted to primary mode, and the other
feed will be demoted to alternate mode.  If, however, the extended
regular expressions are different, then they will both operate
in primary mode.

Here is an example of two feed REQUESTs which are identical as far
as the LDM is concerned:

REQUEST SATELLITE ".*" idd.unidata.ucar.edu
REQUEST SATELLITE ".*" idd.meteo.psu.edu

Here is an example of two feed REQUEST that are not considered to
be identical by the LDM even though they both request exactly the
same set of products:

REQUEST SATELLITE ".*" idd.unidata.ucar.edu
REQUEST SATELLITE "(.*)" idd.meteo.psu.edu

In the first case, the fastest feed will get promoted to primary
mode and the slower feed will get demoted to alternate mode.  If/when
the speeds of delivery from both are upstreams are more or less equal,
then the machines assuming the primary and alternate roles will
ping-pong back and forth.

In the second example, both feeds will stay in primary mode.  The
local LDM will get all products from both feeds, and the second
of each product received will be thrown away since its twin will
have already been written into the LDM queue. This is what we refer
to as the LDM's duplicate product detection and rejection feature.
We use this mode pretty much exclusively as we are willing to sacrifice
network bandwidth for a guarantee of getting everything.

re:
> Then indeed just the restart could be what fixed it.

Yup.

re:
> Thank you for educating me. It seems I always knew it wrong.

No worries.

It strikes me that the REQUEST lines you have on your machine(s)
might still have the PRIMARY and ALTERNATE/SECONDARY indicators
at the end of the REQUESTs.  The use of these indicators was done
away with quite a long time ago, but they do no harm.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: SER-849220
Department: Support IDD
Priority: Normal
Status: Closed
===================
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