Yes indeed. With this change, we see replication on all three subscriber
nodes in the 2-5 secs range per SYNC event. (We’re configured with the
2-sec default.) Without it, the subscribers spend most of the day
paralyzed, with sporadic blocks of some minutes of consciousness which
they use to frenetically catch up.
	Figure I’ll await others’ comments and then post excerpts to bug 336.
Your point on not impacting others’ workloads is very well taken. A
non-default runtime option seems like the right way forward.

	Tom    :-)


On 11/20/15, 8:45 AM, "Steve Singer" <ssinger at ca.afilias.info> wrote:

>On 11/19/2015 01:09 PM, Tignor, Tom wrote:
>> 	A general question for the group: if we would consider a change like
>>this
>> (as a runtime option or otherwise), what’s the correct way to move it
>> forward? Should I file a bug? Are there specific tests or analysis which
>> should be performed?
>
>I would use bug 336 for this.
>My gut is to make this a runtime option since I am not confident that
>downgrading the isolation level won't impact someones workload, having
>said that I am open to being convinced otherwise.  I would also be
>inclined to leave the default value unchanged for 2.2.x and then maybe
>consider changing the default in 2.3.   If we actually any concrete
>plans for a 2.3 version I would say just leave the change for 2.3 but I
>don't see a 2.3 release happening soon and I don't want to change the
>default behaviour in a minor release.
>
>
>Generally when we make a change like this I try to do lots of runs
>through the disorder/clustertest suite that doesn't cover all types of
>workloads.  Have you tried this change on your workload? Does it
>actually help things?
>
>It would be great if Jan and Chris were to comment on this thread
>
>> 
>> 	Tom    :-)
>> 
>> 
>> On 11/18/15, 10:35 AM, "Greg Sabino Mullane" <greg at endpoint.com> wrote:
>> 
>>> On Wed, Nov 18, 2015 at 02:26:15PM +0000, Tom Tignor wrote:
>>> ...
>>>> Sorry for the delay getting back. Inspired by your questions, I¹ve
>>>>been
>>>> reading up on SSI, the Cahill paper and slony1 and postgres code.
>>> ...
>>>
>>> It should be pointed out that 9.1 goes EOL (End of Life) in less than
>>> a year (Sep 2016), and transaction handling has changed a *lot* since
>>> then,
>>> so any changes that core Slony makes may not even work for you.
>>>
>>> (FWIW, I think dropping the isolation level in this particular
>>> instance seems safe, however.)
>>>
>>> -- 
>>> Greg Sabino Mullane greg at endpoint.com
>>> End Point Corporation
>>> PGP Key: 0x14964AC8
>> 
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>> 
>