On 10/22/2016 03:13 PM, bruce wrote:
> I've thought of having a "pid" file on the nfs, where each clientApp
> would reset/lock/use the pidFile to then get/use/delete the file as
> required, but this seems tb slow.. but doable.
I would experiment with using the atomicity of the filesystem rename.
The process on client number N will do:
1) list files in directory
2) identify a filename not starting with "INPROGRESS-" (e.g. "abcd"); if
file-not-found {sleep(something); goto 1}
3) rename "abcd" to "INPROGRESS-N-abcd"; if file-not-found goto 2
4) process INPROGRESS-N-abcd
5) delete INPROGRESS-N-abcd
6) goto 1
The rename is atomic, so if two processes try to grab the same file, only one
wins
the race; when a file has been renamed, nobody else can mess with it.
The good part is that you do not need anything running on the server.
Of course you have some tunables; sleep could be 0.01s or 1m, depending
on your expectations; "INPROGRESS-" could be a smarter Unicode prefix,
for example "⚒".
(alternatively, keep the name unchanged but rename the file away to
a client-specific directory)
Just be sure that rename maintains the atomicity for the NFS implementation
and version you are using.
Regards.
--
Roberto Ragusa mail at robertoragusa.it
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