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[McIDAS #ILV-152686]: What is nexraget?



Hi Mike,

re:
> What is nexraget?  It's clearly related to processing level3 data but
> beyond that we weren't sure.

'nexraget' is an ADDE 'get' server.  'nexradir' is an ADDE 'dir' server.
When one sets up an ADDE server for local NEXRAD Level 3 data, an IMGLIST
will cause 'nexradir' to be run to create the list of files that are
in the dataset.  'nexraget' will be run from an IMGDISP invocation to
send back the NEXRAD Level 3 data requested.

re:
> The reason why I'm asking is because we are attempting to troubleshoot an
> intermittent issue on our server involving high load.  One of the pieces of
> evidence includes seeing nexraget processes with a high i/o usage (via
> iotop).  They only seem to appear like this when load is excessively high
> and aren't sure if it's a symptom or a cause.

It might be both especially if the dataset being interrogated has a large
number of members (i.e., lots of the type of NEXRAD Level 3 product being
requested).

re:
> Figured gaining an
> understanding of what nexraget actually does would be a good place to start.

Given the potentially large number of elements/members of a NEXRAD Level 3
dataset, it is usually a good idea to create subsets to cut down on the
file cracking that the 'nexradir' and 'nexraget' process have to do.
We accomplish this on our ADDE servers by writing the Level 3 products
into directories organized by day and type and setup our ADDE datasets to
point to a single day unless they are deemed to be "archived".  Keeping the
numbers of files down to a minimum keeps the 'nexradir' and 'nexraget'
overhead down to a minimum.

re:
> Thank you!

No worries.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: ILV-152686
Department: Support McIDAS
Priority: Normal
Status: Closed
===================
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