Re: Question on File locking

Another approach is to serialise the writes by using a data queue.
The clients each write the entry to a data queue, and there is one
never ending program that reads the data queue and actually writes to
the disk file. This works great unless the client needs to know the
sequence number.
--buck

On 11 August 2014 21:49, Ken Sims <mdrg8066@xxxxxxxxxxx> wrote:

Hi Vinay -

On Mon, 11 Aug 2014 16:58:16 -0400, Vinay Gavankar
<vinaygav@xxxxxxxxx> wrote:

There is only one program that is writing to this file, but is running
concurrently.

What would be a fool-proof way of writing to the file without having to
trap for error on write and looping.

For example, when getting the lowest sequence, I can keep that record
locked, and then write a record with a lower sequence and then unlock the
file.

You could have a record in another file that the program chains to
first, and holds the lock until the entire CHAIN/subtract/WRITE
sequence is done. This serializes the processing so that there may be
multiple instances of the program running simultaneously, but only one
at a time can add a record.

Ken
Opinions expressed are my own and do not necessarily represent the views
of my employer or anyone in their right mind.
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