[Bucardo-general] KID dies with 'could not serialize access due to concurrent update' (prevents replication)

[Bill McGonigle]

On 12/08/2011 11:15 PM, Greg Sabino Mullane wrote:
> You came across one way to solve this: block other processes that are 
> updating the tables in question at the same time.

Yeah, but there's still something I haven't resolved in my mind - which
is that as soon as I let those processes back in, the 'concurrent
update' problem immediately recurred and replication stopped happening
again (which is very unusual).

I suspect I could have kept locking the clients out, letting bucardo
finish, etc.  But, after rebooting the vm, that wasn't necessary
anymore.  I'd already restarted bucardo and postgresql several times
without improvement, so rebooting the host OS was the changing variable
that made everything work normally again.

But I have no explanation for why rebooting the vm would make those
concurrency problems stop happening.  I'm identifying the 'concurrent
update' errors as not coincidental in this particular case since they
coincided exactly with replication failure in the logs and stopped
appearing in the postgresql log files (error statement logging on) after
the reboot.

> If you create
> a file named /tmp/bucardo-force-lock-foobar, where foobar is the name
> of your sync, Bucardo will attempt to lock all the tables involved in
> the sync at the start of the transaction.

Cool - that's much handier than futzing around with a bunch of iptables
rules!  If this ever happens again I'll start there.  Is the file
checked for on each sync run?

-Bill

P.S.  Thanks for all the suggestions for improvements - I'm tentatively
planning on a Bucardo 5 upgrade after the holidays and a platform
upgrade later in the year (newer PostgreSQL then).  Is there a current
list of reasons why Bucardo 5 might not be ready for production in some
cases?  I've been following the list traffic on it, and it looks from
here to have greatly matured (and I love the new architecture).

-- 
Bill McGonigle, Owner
BFC Computing, LLC
http://bfccomputing.com/
Telephone: +1.855.SW.LIBRE
Email, IM, VOIP: bill at bfccomputing.com
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