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[LDM #MWC-865643]: PQACT Utility


> Steve,
> Thanks for responding.

No worries. That's why were here. :-)

> We have the EXEC statements defined and they work for other experimental 
> products.  Just so I understand, I cannot use pqact from the command-line to 
> process a product that is currently in the queue?

You can use pqact(1) from the command-line -- it's just not intended to be used 
that way for performance reasons. When a data-product is inserted into the 
product-queue by a downstream LDM process, a SIGCONT is sent to the LDM 
server's process-group and received by all pqact(1) processes that were creates 
as a result of EXEC entries in the LDM configuration-file. This signal causes a 
pqact(1) process to "wake up" and check the product-queue for the added 
product. This type of "even driven" design performs much better than having the 
pqact(1) processes poll the product-queue for added products.

As a fail-safe measure, a pqact(1) process *will poll* the product-queue if it 
doesn't receive a SIGCONT for 15 seconds. So a pqact(1) process that's external 
to the LDM process-group will still work -- just not as efficiently (there will 
be, on average, a 7.5 second delay in processing data-products). This 
polling-interval is settable via the "-i" option (a polling-interval of 0 will 
cause the pqact(1) process to terminate when it reaches the end of the 

I hope this helps.

> lb

Steve Emmerson

Ticket Details
Ticket ID: MWC-865643
Department: Support LDM
Priority: Normal
Status: Closed

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