[ldm-users] 20080216: Nexrad Level 3 (cont.)

Jeff and Tyler,

re: are you seeing any disconnection/reconnection messages in your
~ldm/logs/ldmd.log file"

Jeff wrote:
>No, But Im seeing what Tyler is seeing a lot of flip flop between weather2 
>and bigbird, it seems to be happening at the top of the hour,

The version of the LDM that Jeff is using, LDM-6.6.5, will switch among
redundant feeds to the one that is providing data the fastest. When two
or more machines are delivering data at rates that are very close to
each other, there can be a lot of "flip flopping".  There should be no
loss of data _if_ the sequence of products is the same on the upstream
hosts, AND if the system clock is accurate.  As I noted in my two
previous emails, Jeff's clock is not accurate; this is why I pointed
out the strong recommendation to switch from ntpdate (or equivalent)
to use of ntpd.

>some of my
>users are reporting since around 13z most if not all the sites just stop

I am not familiar with your setup.  Are you relaying the Nexrad Level
3 data to other sites using the LDM?

If you are not relaying using the LDM, what are you referring to by
"all the sites just stop updating"?  Updating where and how?

Again, at least for the current period of 00:57 - 01:10Z, the rate of
receipt of Nexrad Level 3 products by the LDM on your machine,
level3.michiganwxsystem.net, is equivalent to a machine at the UPC that
is getting the data one hop away from a NOAAPort ingest box.  It is
because of this that I am trying to determine what measure you are
using to determine that there is a burstiness of the data.

>then about 5 after I get slammed with all the missed data,

At 00:57Z on the 17th I began watching the output of:

notifyme -vxl- -f NNEXRAD -h level3.michiganwxsystem.net

and I saw a steady stream of Level 3 products being received by your
LDM.  Comparison with receipt on your system and one at the UPC shows
the ingest to be comparable -- no big delays; no gaps; similar receipt

>looking back in the logs I see this .. from about 10 to the top of the hour 
>to about 5 after there is very little L3 data incoming,

Which logs?  What is your pqact pattern for processing the Level
3 products you are receiving?

>then its like the flood gates open and all the L3 data is 

I have not seen this burstiness in the period 00:57Z - 01:15Z.  From
your prespective, have things changed?


* Tom Yoksas                                            UCAR Unidata Program *
* (303) 497-8642 (last resort)                                 P.O. Box 3000 *
* yoksas@xxxxxxxxxxxxxxxx                                  Boulder, CO 80307 *
* Unidata WWW Service                            http://www.unidata.ucar.edu/*

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