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20050321: combining ldm feeds

>From: Rob Cermak <address@hidden>
>Organization: IAF
>Keywords: 200503220201.j2M21Zv2023898 LDM ldmd.conf request


>Is it ok for a single machine to ingest more than one feed from multiple 
>locations?  No queue complications?

Yes, it is fine to do this, and no, there are no queue complications.

In fact, many sites use this feature to setup redundant feeds for
greater reliability.  For instance, if in your example both rossby
and yukon have the IDS|DDPLUS data and you aren't overly concerned about
bandwidth use, you might consider the following:

request IDS|DDPLUS      ".*"   rossby.met.sjsu.edu      PRIMARY
request IDS|DDPLUS      ".*"   yukon.net.images.alaska.edu      PRIMARY

If you find that you always get the data faster from yukon than from
rossby and you are concerned about bandwidth use, you could use:

request IDS|DDPLUS      ".*"   rossby.met.sjsu.edu      ALTERNATE
request IDS|DDPLUS      ".*"   yukon.net.images.alaska.edu      PRIMARY

The difference between PRIMARY and ALTERNATE (aka SECONDARY) feeds is
PRIMARY tells the upstream to send the data whenever it has it; ALTERNATE
tells the upstream to ask if you want the data product-by-product.
As you might imagine, the transactions in an ALTERNATE request make
the delivery of data slower.

>One machine has:
>  request IDS|DDPLUS   ".*"   rossby.met.sjsu.edu
>Another has:
>  request HDS  ".*"   yukon.net.images.alaska.edu
>May I combine both feeds on one machine with this in ldmd.conf?
>  request IDS|DDPLUS   ".*"   rossby.met.sjsu.edu
>  request HDS  ".*"   yukon.net.images.alaska.edu

Yup, absolutely no problem.  Just make sure that the upstream sites
have allowed your machine to request data that you want.


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