[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[LDM #WYF-519931]: LDM - Future use of LDM for next generation GOES

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: [LDM #WYF-519931]: LDM - Future use of LDM for next generation GOES
  • Date: Fri, 21 Jul 2006 14:06:32 -0600
Daniel,

> I am sorry to continue to bother you.  I seem to be getting pieces of
> questions that I have.  I don't know if you prefer the multiple e-mails
> as I come up with additional questions, or would you prefer a large load
> of questions.

I prefer single-topic questions.

> But assuming that you are OK with a bunch of e-mail questions, I have
> another.
> 
> Is there a white paper that describes how an upstream LDM server handles
> distribution to a failed LDM server.

There's no white paper on the subject.  The previously-mentioned "LDM Basics"
webpages describe the operation of an LDM.  Basically, if a downstream LDM
child process terminates, then the corresponding upstream LDM child process 
also terminates.

>  How a downstream LDM server handles a full local disk.

The only component of an LDM system that cares about a full local
disk is the pqact(1) utility (assuming it's filing data-products to the
disk).  The LDM server and child upstream and downstream LDM
processes don't write to local disk (other than the LDM log file).

If the pqact(1) utility can write to a local disk because the disk is
full, then it will log an error message and continue with the next
data-product.

> How an LDM server handles downstream LDM
> servers that are bogging down the upstream LDM server.

Because the LDM server spawns an upstream LDM child process
for every request by a downstream LDM, the outgoing data
connections are very independent of one another.

> Is it a correct statement to says that a product queue is set-up to hold
> a certain length of time for a data set.  Once the data set time period
> is over, the data is no longer available via the LDM server.

The product-queue is a fixed-size, memory-mapped file.  It it limited by
two things, the number of data-products that it can hold and the amount
of data that it can hold.  These two parameters are individually settable
and are specified when the product-queue is created.

> Thanks again for your help, Have a great weekend.

You're welcome.  Same to you.

Regards,
Steve Emmerson

Ticket Details
===================
Ticket ID: WYF-519931
Department: Support LDM
Priority: Normal
Status: Closed