Ensuring in-order execution

[John Goerzen]

Hi,

I'm wondering if there are any generic programs out there to help ensure
in-order execution.

My particular use case: sending incremental backups over NNCP, though this is
the same problem as sending them over UUCP; namely, that nncp-exec/uuxqt aren't
able to make guarantees about executing commands in order, since they may arrive
via varying paths, etc.

I've worked around this in a couple of ways:

1) When using ZFS incrementals, zfs receive detects the out of order situation
and exits with an error.

2) When using tar or dar incrementals, I keep a "last processed" file on both
the sender and recipient, and part of the request references the sequence number
of the previous file, so the wrapper script can verify that before proceeding.

It's this situation #2 that I think must certainly have some generic solution,
as I keep seeming to reinvent it every few months. I'm sure that in the earlier
days of Unix and UUCP, this was a fairly common problem and it seems to me that
a generic solution must exist, but my searching has been futile so far.

Any ideas welcome.

Thanks,

John

[John Goerzen]

I eventually decided to write something to solve this:

https://changelog.complete.org/archives/10368-fast-ordered-unixy-queues-over-nncp-and-syncthing-with-filespooler