[Support #RQS-322086]: LDM Feedtype Questions

Jon,

> My name is Jon Hurst, I work with James Pelagatti at MIT/Lincoln
> Laboratory.  We are currently altering our LDM setup so we can serve
> some internal data to outside organizations and we had some questions
> about how to choose a feedtype.   I realize that we could technically
> choose any feedtype, and for testing we have been using EXP and also
> FSL2, but in the long term perspective we were thinking it might be
> worth establishing our own feedtype for the Lab.  If we do not create
> our own feedtype, I suppose we'll have to piggyback off of some other
> feed, or perhaps use the default ANY or EXP feedtypes.  Here are my
> questions in a semi-concise form:
> 
> - How frequently are new feedtypes added and when does a distribution
> site qualify for its own feedtype?  Might we qualify?

The LDM feedtype is represented as a 32-bit, unsigned integer with each
bit corresponding to a primitive feedtype.  As a consequence, only 32
primitive feedtypes are possible.  Increasing the number of feedtypes
would entail a change to the protocol and more than a little bit of
programming.

> - How much work would be involved with adding a new feedtype?  It looks
> like we would need to modify atofeedt.c, ldm.h and feedtypes.xml.  I
> guess the problem is ensuring that clients connecting to our server have
> a version of ldm that recognizes our new feedtype.  Is it common
> practice to use the ANY or EXP feedtype in the short term with the goal
> of switching to a unique feedtype upon the arrival of the next LDM version?

I suggest using the EXP feedtype and choosing your product-identifiers very
carefully so that they uniquely identify the data-products and are easily
selected via regular expressions.  We, typically, recommend that the first
component of such a product-identifier be an institutional or project name.

> Any feedback would be very helpful.  Thank you for your time.  LDM has
> been a great help!

I'm glad to hear that.

I'm currently working on an LDM replacement that won't have a problem with
a limited number of feedtypes.  Unfortunately, it won't be out until next
year.

Regards,
Steve Emmerson

Ticket Details
===================
Ticket ID: RQS-322086
Department: Support LDM
Priority: Normal
Status: Closed