[LDM #BVM-113085]: Question about NEXRAD Level II data

Hi Niles,

re:
> We are using NEXRAD level II radar data delivered via
> LDM. The general idea of these files is that you read a header,
> then read data from the file (the number of bytes having been
> specified in the header) and then use the bunzip2 library to
> unzip this buffer.
> 
> This has worked well for us for a number of years.
> 
> What we're seeing now, though, is that for a small
> percentage of the files the buffer will not unzip. It's as
> if the data has been corrupted in some way. It's very odd,
> since the buffer to unzip does appear to start with
> what looks like the BZ compression library header.
> 
> So it looks like it should uncompress - and over 99% of the
> files do uncompress OK - but a small percentage do not.
> 
> My questions are :
> 
> * I don't think that the LDM is somehow corrupting the
> files, but could that be?

It shouldn't.  The LDM is product-content agnostic (i.e., it
doesn't do anything to a product's contents or care what
those contents are).

> I've attached the etc/ directory
> from our LDM so you can see if we've done anything odd.

I looked through your ldmd.conf and pqact.conf files and see
nothing wrong.

> * Would you have any idea about who to contact about what is
> getting inserted into the LDM queue? I suspect that there is
> problem with the data that are getting pqinsert'ed rather than
> the LDM.

First, let's verify that there isn't some other problem.  Can
you send us a (or a couple) of the files that won't uncompress
on your system?  It would be most useful if you could send the
file(s) as soon as you receive them/notice that they are bad
so that we can do a bit-for-bit comparison of what you received
and what we received.  Thanks in advance...

> Thanks very much,

No worries.

> Niles Oien, RAL


Cheers,

Tom
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Ticket Details
===================
Ticket ID: BVM-113085
Department: Support LDM
Priority: Normal
Status: Closed