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[LDM #REX-234477]: iowa LDM

Hi Bongchul,

re:
> Thank you for your quick answers, but I have some more questions.

Ready...

re:
> Although we requested all radar data in ldmd.conf, we are actually
> getting data specified in pqact.conf which are seven radar data.

You are definitely receiving all of the NEXRAD Level 2 data.  This
can be seen from the NEXRAD2 volume plot on our IDD statistics pages:

Unidata HomePage
http://www.unidata.ucar.edu

  Projects -> Internet Data Distribution
  https://www.unidata.ucar.edu/projects/index.html#idd

    IDD Current Operational Status
    https://www.unidata.ucar.edu/software/idd/rtstats/

      Statistics by Host
      https://www.unidata.ucar.edu/cgi-bin/rtstats/siteindex

        s-iihr52.iihr.uiowa.edu [6.8.1]
        
https://www.unidata.ucar.edu/cgi-bin/rtstats/siteindex?s-iihr52.iihr.uiowa.edu

Part of the 'volume' plot for NEXRAD2 is a list of the sites contributing
to the data you are receiving.  As you will see, the list is long enough that
it does not entirely fit on the plot.

As to what data you are processing, this is entirely controlled by 
pattern-action
file actions.  A quick look at the pqact.conf file you sent in a previous
email shows that you are, in fact, only processing a small fraction of the
radars that you are receiving.

re:
> Can this affect our system performance (e.g., memory usage)?

The receipt of large volumes of data will manifest itself in several ways:

- network bandwidth use

- memory use based on the size of the LDM queue

- how that data is processed

You are definitely using more bandwidth getting the data than your
pattern-action file actions indicate that you are actively using.

NB: one question needs to be answered _before_ you decide to
reduce your NEXRAD2 REQUESTs:

- is the data being received by s-iihr52.iihr.uiowa.edu being
  relayed to other machines?

  If yes, then you probably need to keep REQUESTing all of the
  data.

re:
> We definitely do not need all radar data since Hydro-NEXRAD is not running 
> now.

OK, that is news to us.  We were under the (perhaps incorrect) impression
that all of the data was still needed/wanted.  Again, Anton Kreuger should
be able to speak definitively on this point.

re:
> Is there any way that we can modify ldmd.conf to get data from specified
> radar sites in pqact.conf?

Yes, this is easy to do.  Here is one example of how to do this:

change your existing ~ldm/etc/ldmd.conf REQUEST lines from:

REQUEST NEXRAD2 ".*" idd.unidata.ucar.edu PRIMARY
REQUEST NEXRAD2 ".*" idd.aos.wisc.edu ALTERNATE

to:

REQUEST NEXRAD2 "^L2-BZIP2/(KDVN|KDMX|KMPX|KARX|KOAX|KFSD|KEAX)" 
idd.unidata.ucar.edu
REQUEST NEXRAD2 "(^L2-BZIP2/(KDVN|KDMX|KMPX|KARX|KOAX|KFSD|KEAX))" 
idd.aos.wisc.edu

Comments:

- the 'PRIMARY' and 'ALTERNATE' items at the end of your REQUEST lines
  have no meaning in current versions of the LDM (you are running v6.8.1
  which ignores these qualifiers)

- I surrounded the second REQUEST pattern with '()' (parentheses) to make
  it different from the first pattern.  This is the way that REQUESTs
  are forced to run in primary mode in current versions of the LDM

- in order to make any change made in ldmd.conf active, one has to stop
  and restart the LDM:

  <as 'ldm'>
  ldmadmin stop
  ldmadmin start

  OR

  ldmadmin restart

re:
> I appreciate your help.

No worries.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: REX-234477
Department: Support LDM
Priority: Normal
Status: Closed