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20040113: LDM Buffering Question

Chris,

>Date: Mon, 12 Jan 2004 17:41:00 -0600
>From: "Chris D Gilbert" <address@hidden>
>Organization: US DoC/NOAA/NWS/NEXRAD OSF
>To: Steve Emmerson <address@hidden>
>Subject: LDM Buffering Question

The above message contained the following:

> I have a question about LDM buffering.  What happens when the upstream
> server requests data from the downstream server.

Do you have your "upstream" and "downstream" concepts reversed?  A
downstream LDM requests data from an upstream LDM.

> Will all of the data in the
> queue be transmitted, or only data from the time of the request on... Is
> this configurable?

Details of downstream LDM behavior can be found at 

    
http://my.unidata.ucar.edu/content/software/ldm/ldm-6.0.14/basics/behavior.html

Search for "Downstream LDM 6 behavior".  Basically, it will use the
argument of the "time offset" option, if it exists; otherwise, it will
use the time of the more recent existing product in the product-queue
that matches the selection criteria; otherwise, it will use one hour
ago.

> Say an upstream server goes off line for 10 minutes. Will it miss data for
> the entire 10 minutes or will it try to "catch up".

It will try to "catch up".

> The queue by default is 20MB. right?

I believe the default is 200 MB.

> I assume it will buffer up to 20MB worth of data?

The size of the dowsteam product-queue, in this situation , is less
important than the size of the upstream product-queue.

> Any information or links to documentation will be appreciated.

I highly recommend the following:

    
http://my.unidata.ucar.edu/content/software/ldm/ldm-6.0.14/tutorial/index.html
    http://my.unidata.ucar.edu/content/software/ldm/ldm-6.0.14/basics/index.html

> Chris Gilbert, ROC Software Engineer
> Phone: (405) 366-6520 Ext. 4246 / Fax (405) 366-6543
> E-mail: address@hidden

Regards,
Steve Emmerson