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20050510: [Fwd: Re: [SCOOP_Version2] "Quick" LDM Question]



Gerry,

If you are using the program "pqinsert" to place a file into your queue
that is identical to one already in the queue (same MD5 checksum), then
it will be rejected with a PQ_DUP (-2) log message. This extends across
feedtypes, since the checksum only takes into account the data contents and
not the feedtype associated with a product.

If you really want the same product in the queue multiple times, then
what I have done is append the file name and/or current time at the end of the 
file
to make the file unique (eg add a meta tag like <filename inserted at `date 
-u`>).
That way, the MD5 calculated on the file contents will be unique.

Otherwise, you could use "ldmsend" to send point to point to a host without 
using
a local queue (the downstream would need an "ACCEPT" line in its ldmd.conf) if
you wanted to direct the flow from the upstream, rather than a downstream 
connection.
That would avoid a local product queue trying to service multiple downstream 
feeders.

Steve Chiswell
Unidata User Support




>From: Gerry Creager n5jxs <address@hidden>
>Organization: AATLT, Texas A&M University
>Keywords: 200505101647.j4AGlmP3014869

>Howdy!
>
>We're using LDM to move a lot of ocean models, NAM-awip32/awip12 and MM5 
>data around, as well as some DDPLUS and CRAFT data, for the SCOOP 
>project.  <Tom knows this; historical background>
>
>We're doing both the 2005 hurricane season and some retrospective 
>storms.  We're running into a problem with inserting files with 
>similar/identical checksums into the queue.
>
>Might y'all be able to shed some light on what we *should* be doing?
>
>Thanks,
>Gerry
>
>-------- Original Message --------
>Subject: Re: [SCOOP_Version2] "Quick" LDM Question
>Date: Tue, 10 May 2005 10:17:50 -0500 (CDT)
>From: David Forrest <address@hidden>
>Reply-To: David Forrest <address@hidden>
>To: Gerry Creager N5JXS <address@hidden>
>References: <address@hidden> 
>                    <address@hidden> 
>                       <address@hidden> 
>      <address@hidden> 
>         <address@hidden> 
>          <address@hidden> 
>          <address@hidden> 
>        <address@hidden> 
>        <address@hidden> 
>      <address@hidden> 
><address@hidden> <address@hidden>
>
>On Tue, 10 May 2005, Gerry Creager N5JXS wrote:
>
>> LDM doesx check based on both checksum AND filename.
>
>Hi Gerry, do you mean something like:
>
>with:  x = "n't"      for pqinsert
>          = ""         for actual transport    ??
>
>One of the problems we noticed in testing was that we couldn't re-pqinsert
>a constant test file, even if it had a different filename.  Justin posted
>a test case on this thread earlier, and Justin and I are sending 'EXP
>test.*time' feeds to work around it.  For pqinsert, it seems the
>data/md5sum has to be different, which caused problems for one of the
>theoretical retrospective cases we considered.
>
>Dave
>-- 
>  Dr. David Forrest
>  address@hidden                                    (804)684-7900w
>  address@hidden                             (804)642-0662h
>                                    http://maplepark.com/~drf5n/
>
>-- 
>Gerry Creager -- address@hidden
>Texas Mesonet -- AATLT, Texas A&M University   
>Cell: 979.229.5301 Office: 979.458.4020
>FAX:  979.847.8578 Pager:  979.228.0173
>Office: 903A Eller Bldg, TAMU, College Station, TX 77843
>
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