On 12/8/2005 9:31 AM, cbbrowne at ca.afilias.info wrote:

>> On 12/7/2005 9:23 PM, Peter Davie wrote:
>>> Hi All,
>>>
>>> Using Slony1 version 1.1.0 at a customer site, the customer has had the
>>> slon daemons fall over on one of their slave servers (and didn't
>>> notice!)  On restarting the slon processes, there is now an error being
>>> generated because it is attempting to malloc memory to record all of the
>>> outstanding transactions and the slon daemon is running out of memory.
>>> Is there any way forward to resolve this, or will I just have to
>>> uninstall the slave and resubscribe (which is my current plan).
>>
>> This node must have been down for quite some time. A SYNC event in the
>> remote_worker queue takes about 200 bytes or so. How many million events
>> is this node behind? You could tell from looking at sl_status.
>>
>> And don't forget to VACUUM FULL ANALYZE that database after you've
>> dropped that node.
> 
> Based on the symptoms, two things come to my mind:
> 
> 1.  Did the slon controlling the origin die?  That would be the classic
> way for a SYNC to encompass a Very Long Period Of Time and hence a LOT of
> transactions.

That's not the case and it wouldn't cause the symptom observed. Unless 
there are large rows involved, the resulting, humungous sync chunk would 
just take a while, but since that operation is cursor driven even in 
1.0, it won't cause slon to run out of memory.

> 
> There's a script in ~/tools that will generate SYNCs if you run it as a
> cron job.  We run this in production so as to avoid this particular
> problem...
> 
> 2.  Is it possible that the subscriber is trying to process a whole bunch
> of SYNCs in one fell group?
> 
> If you add the "-g 1" option, it'll go one SYNC at a time, which would
> somewhat alleviate the problem.

Would not be a problem either.


Jan

-- 
#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
#================================================== JanWieck at Yahoo.com #