[ic] Order Numbers and NFS

[Kevin Walsh]

Sandy Thomson <sandy at scotwebshops.com> wrote:
> I have been having issues with clustering interchange and using the 
> default order counters.
> 
> Now it all works pretty well with file based sessions at the moment - 
> until the early morning cron job that expires old sessions kicks in on 
> the NFS master (and the NFS slave has to 'catch up'). Any changes to the 
> order counter file get queued up with all the other writes, and there is 
> the problem of the order counter getting out of sync. It has happened 
> before, we have had a few duplicate orders but there was no way to pin 
> down the exact cause of the problem (I always suspected this though). 
> Anyway last night over the space of 2 hours we had 6 orders assigned to 
> 3 order numbers.
> 
> The solution I would like to use is database sequences. I have been 
> trawling through the documentation/mailing lists for a few hours, have 
> tried making my own UserTags and referencing them in the CounterFile 
> directive, have also tried setting $Value->{mv_order_number} in 
> etc/log_transation to no avail.
> 
> I also noticed the [counter] tag has sql options for sequences, so im 
> guessing the work for this must already be done?
> Any hints?
> 
Please check that you have set the following configuration directives
to make use of fcntl, instead of the default flock, when locking files
exported over NFS:

In interchange.cfg:

    LockType  fcntl

In catalog.cfg:

    SessionType  NFS

Locking problems would only occur when there are multiple simultaneous
attempts to access a file, of course.  You said that you had six orders
over two hours, and three order numbers.  It seems a bit of a coincidence
to get simultaneous writes to the order counter file during that time,
but not impossible, so you should check the order times to verify whether
this is a locking issue or something else.  Raising some test orders
will help track the problem, if it's not lock-related.

If you'd prefer to use SQL counters, with the [counter] tag, then
you will find some documentation in section 4.16.2.4 of the
Interchange Tags Reference, here:

    http://www.interchange.rtfm.info/docs/rtfm_ictags.html

Also, in your main Route, you can use SQL order counters by setting
the "sql_counter" key.  The specified value would be passed to the
same subroutine that looks after the [counter] tag, so the same
syntax listed in the above [counter] documentation will apply.

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