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Re: 20050526: sequential running

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  • Subject: Re: 20050526: sequential running
  • Date: Thu, 26 May 2005 10:28:54 -0600
Angel,

> To: address@hidden
> From: "Angel Corona" <address@hidden>
> Subject: sequential running
> Organization: UCAR/Unidata
> Keywords: 200505252230.j4PMUSP3005035

The above message contained the following:

> We are decoding metars into netCDF files. Is there a way besides the 
> -wait tag for exec to make sure that only one instance of the decoder is 
> being run at a time?

The "-wait" option of the EXEC action is necessary to guarantee that
only one child-process associated with the given entry is being
executed.

> We would much rather use pipe over the exec funtion.

One can use the PIPE action rather than the EXEC action to improve
performance if the decoder is written so that it

    1.  Can read a sequence of data-products from the standard-input
        stream (i.e., it must be able to identify the beginning and end
        of the data-products for which it is the decoder).

    2.  Terminates after some reasonable time interval (e.g., 10 
        minutes) if there's nothing to read.

If the decoder can only read one data-product from the standard-intput
stream, then one can still favor the PIPE action over the EXEC action 
if the "-close" option is specified -- the performance improvement just
won't be as great.

> Thanks
> Angel Corona
> 
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> org:National Weather Service - Alaska Region;Systems Integration Branch
> adr;dom:;;222 W. 7th Ave. #23 Rm. 517;Anchorage;AK;99513-7575
> email;internet:address@hidden
> title:Special Applications Program Manager
> tel;work:(907)271-4428
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> 
> --------------040303020709080706010801--

Regards,
Steve Emmerson

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