Re: 980218: FEED type abuse

>To: address@hidden
>From: "Mark J. Fenbers" <address@hidden>
>Subject: FEED type abuse
>Organization: Ohio River Forecast Center
>Keywords: 199802182339.QAA13701 LDM feed type
>
> We currently use the AFOS data feed to share and manage products
> ingested from AFOS, but we also want to use LDM to manage a variety of
> locally-generated products such as postscript maps or our own types of
> gridded data.  We do this successfully using pqinsert with the feedtype
> of EXP, but that is getting confusing with a number of our LDM-socket
> sites also sharing and managing different data under the same EXP feed
> type.  Feedtypes of AFOS and EXP are the only feedtypes we use
> currently.
>
> I understand that if using an ingester, the purpose of the feedtype
> would be to define the protocol so that pqing knows how to recognize the
> start and end of a product.  But once the product is already in the
> "lmd.pq" (via pqinsert, ldmsend, etc.), I suspect that the feedtype is
> nothing more than a label used by pqact (and maybe other utils) to help
> organize that data.  Is this accurate?

Yes. One way to think of it is as a simple "routing key"
that is quicker to test on than using the full regular expression on
the product id's. It is also useful to think of it as defining the "namespace"
that the product identifier's live in. The product id's of AFOS products have
different syntax than WMO format bulletins.

> If so, I would assume I could
> insert, say, HTML-formatted text products into the product queue using
> pqinsert and specify any feedtype (so long as it is not in use among the
> other upstream or downstream LDMs).
> Is this true, or are there some
> "gotcha's" in doing this??

Absolutely. That was the idea behind the EXP feedtype. Unfortunately,
there are some ldm networks that are moving EXP data around, so one guys
idea of EXP may collide with another. The feedtype space is 32 bits, and we've
allocated more than half of it. There are some feedtypes which have been
allocated which aren't in public use, however. Like FSL5 and NMC3. See ldm.x
or ldm.h. You might want to use one of these if you are getting EXP pollution.

> Mark
> - --
> address@hidden
>
> Remember when "space characters" used to mean...
>       ...little green beings in UFOs???