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[Datastream #GFZ-680741]: missing nogaps fields



Hi Brian,

I apologize for not getting back to you before now...

re:
> We request nogaps gribs via ldm from usgodae3.fnmoc.navy.mil, and for the
> past week we have been noticing some missing fields. For example, last
> night the 2006061400 nogaps is missing the PRMSL (slp) field at f00, f12,
> and f36. We have not changed anything on our end, so I wonder if you can
> please check your nogaps file, or contact fnmoc to see if they have had
> some issues.

I notice that you are receiving alot of data on the machine that is
requesting FNMOC data:

thunder.msrc.sunysb.edu
http://www.unidata.ucar.edu/cgi-bin/rtstats/rtstats_summary_volume?thunder.msrc.sunysb.edu

It is possible that you are not processing the data out of your LDM
queue fast enough to ensure that data in the queue does not get overwritten
by new data being received during peak ingest periods.  In order to determine
if you are losing data out of the LDM queue, please check the following:

- the size of your LDM queue.  Your peak ingest rate is just about 2GB/hour.
  If your queue is undersized (many sites never increase their queue size
  above the 400 MB default), you can easily lose data (not process, that is)
  that you have successfully received

- you can get more information from the 'pqact' invocation(s) that are 
processing
  data out of your LDM queue by putting it(them) into verbose logging mode
  by sending the process ID a 'kill -USR2' signal.  The first 'kill -USR2'
  puts 'pqact' into verbose logging mode; the second puts it into debug
  logging mode; the third returns the process to normal (notice) logging
  mode.  Put the process(es) into debug mode when the FNMOC data is being
  received and see how long it is taking to process the data out of the
  queue.

  NOTE: do not forget to leave the debug logging mode!  This mode will
  generate LOTS of output in your ~ldm/logs/ldmd.log file!!

- if you are trying to process all of the data out of your LDM queue
  using a single 'pqact' process, then I can all but guarantee that
  this is the cause of your data loss.  One instance of 'pqact' has
  little chance of processing 2 GB/hour of data

As far as our checking our receipt of the FNMOC data, please alert us
to the next instance where you see data loss (after checking the things
I listed above), and we will see if we missed data.  We can not go back
to the 14th to check since we don't keep the data around for that long.

> Thanks for your time.

Again, I apologize for not being able to get back to you on your inquiry
before now.


Cheers,

Tom
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Ticket Details
===================
Ticket ID: GFZ-680741
Department: Support IDD
Priority: High
Status: Closed


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