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[LDM #UKJ-478572]: REQUEST entries help

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  • Subject: [LDM #UKJ-478572]: REQUEST entries help
  • Date: Sat, 16 Jul 2011 11:04:55 -0600
Hi Bradley,

> We have a site that has a remote LDM upstream host serving data via a T1
> to a downstream client.

A T1? That's relatively low-bandwidth by modern standards. Still, you have to 
work with what you've got.

> We would like to restrict the REQUEST entries
> from the downstream client to limit bandwidth.  I am having difficulty
> with the syntax for the REQUEST statements and was wondering if you
> could assist,
> 
> Previously with an IDD feed we did:
> 
> request IDS|DDPLUS|FSL2 ".*" oliver.unidata.ucar.edu
> request NIMAGE ".*" oliver.unidata.ucar.edu
> request GEM ".*" oliver.unidata.ucar.edu
> request HDS ".*" oliver.unidata.ucar.edu
> request NGRID ".*" oliver.unidata.ucar.edu
> request NEXRAD3 ".*" oliver.unidata.ucar.edu
> request NEXRAD2 ".*" oliver.unidata.ucar.edu
> 
> In this case, we would like, for example, to only request
> SDUS[2345].PGUM for examlpe from an upstream LDM host named cpsbn1-pbp,
> can I do:
> 
> request NNEXRAD3 "SDUS[2345].PGUM" cpsbn1-pbp
> 
> Or what would the syntax be for example if I wanted to do such,

I would do this:

    REQUEST NEXRAD3 "^SDUS[0-9]{2} PGUM" cpsbn1-pbp

I like to capitalize the action name even though it doesn't matter. "NNEXRAD3" 
isn't a valid feedtype. The "^" character anchors matches to the start of the 
product-identifier. There are two digits after the "US" -- which are matched by 
the "[0-9]{2}" -- and those digits are followed by a single space, which is 
then followed by the station identifier. 

A good way to see product identifiers is by a command like

    notifyme -vl- -f NEXRAD3 -h cpsbn1-pbp -o 300

This will print the metadata of NEXRAD3 data-products received by the LDM on 
host "cpsbn1-pbp" for the last 5 minutes.

> and also
> let's say I also wanted to include multiple radars, say, KOAX, KCCX, and
> KDIX would it be similar to the syntax in pqact or does this follow ERE
> and what would be the best approach to improve latency?

Because the situation you describe appears to be bandwidth limited rather than 
CPU limited, separate requests would probably result in the smallest latencies 
(see 
<http://www.unidata.ucar.edu/software/ldm/ldm-6.9.8/basics/tradeoffs.html>):

    REQUEST NEXRAD3 "^SDUS[0-9]{2} PGUM" cpsbn1-pbp
    REQUEST NEXRAD3 "^SDUS[0-9]{2} KOAX" cpsbn1-pbp
    REQUEST NEXRAD3 "^SDUS[0-9]{2} KCCX" cpsbn1-pbp
    REQUEST NEXRAD3 "^SDUS[0-9]{2} KDIX" cpsbn1-pbp

> Thanks
> Brad
> 
> 
> --
> 
> ________________________________________________________________________
> 
> Bradley M. Scalio, RHCE RHCSS
> Principal Engineer w/Honors
> Raytheon MOS - AWIPS Program
> 
> (p) 301-495-2277
> (c) 301-830-0207

Regards,
Steve Emmerson

Ticket Details
===================
Ticket ID: UKJ-478572
Department: Support LDM
Priority: Normal
Status: Closed