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[LDM #TQB-763493]: Receiving "writer-counter of the product-queue is not zero" message



Gregory,

> I've recently installed LDM 6.6.5 and I'm ingesting some data into the
> LDM QUEUE but dropping the data on the floor (i.e. "pqact" is NOT
> running yet).  I'm adding some addition dataflows to the system (e.g.
> NOAAPORT, NIDS radar, etc.).  This system will replace another older box
> with an older version of LDM.
> 
> H*owever, after gracefully shutting down LDM, every time I start LDM the
> following error/warning is displayed:
> *
> 
> [ldmbakng@rhesrv22 ~]$ ldmadmin start
> *The writer-counter of the product-queue is not zero.*  Either
> a process has the product-queue open for writing or the queue
> might be corrupt.  Terminate the process and recheck or use
> pqcat -l- -s -q /ops_local/ldmbakng/data/ldm.pq && pqcheck -F -q
> /ops_local/ldmbakng/data/ldm.pq
> to validate the queue and set the writer-counter to zero.
> Jan 5 22:34:56 UTC rhesrv22.spc.noaa.gov : LDM not started
> [ldmbakng@rhesrv22 ~]$
> 
> 
> 
> If I perform the pqcat and pqcheck commands then LDM starts up fine.
> 
> Do you have any suggestions as to what is causing this routine
> error/warning and how to remove it?

When a process opens the product-queue for writing, a counter in the 
product-queue is incremented.  When the process closes the product-queue, the 
counter is decremented.  If the process terminates abnormally (such as by 
crashing or by having the computer turned off) then the counter won't be 
decremented.  So, when the LDM system starts, the counter should be zero.  The 
fact that it isn't means that some process that had the product-queue open for 
writing terminated abnormally -- leading to a possibly corrupt product-queue.  
The commands given will verify the product-queue and set the counter back to 
zero.  Alternatively, you could delete and remake the product-queue.

If this happens every time (after manually verifying the product-queue and 
resetting the counter) then you have a process that has the product-queue open 
for writing and that terminates abnormally every time.

> LDM is running on a RHEL box:
> 
> [ldmbakng@rhesrv22 ~/logs]$ uname -a
> Linux rhesrv22.spc.noaa.gov 2.6.18-164.6.1.el5PAE #1 SMP Tue Oct 27
> 11:46:58 EDT 2009 i686 athlon i386 GNU/Linux
> 
> Thanks,
> Gregg Grosshans
> NWS / Storm Prediction Center

Regards,
Steve Emmerson

Ticket Details
===================
Ticket ID: TQB-763493
Department: Support LDM
Priority: Normal
Status: Closed