[pgpool-general: 540] Re: load balancing seems to be bottlenecked by performance of master

[David Kerr]

On 05/28/2012 05:55 PM, Tatsuo Ishii wrote:
>> On Mon, May 28, 2012 at 5:23 PM, Tatsuo Ishii<ishii at postgresql.org>  wrote:
>>>> On Mon, May 28, 2012 at 3:54 PM, Tatsuo Ishii<ishii at sraoss.co.jp>  wrote:
>>>>>> What are the reasons for analysing system catalogs on primary server?
>>>>>
>>>>> For example, if a table is a temporary one or not.
>>>>
>>>> Yes, but as I noted, I don't use temp tables at all.  If this is the
>>>> primary justification, then its not doing me any good, and causing
>>>> unnecessary negative performance impact.
>>>
>>> But how does pgpool know that you are not going to use temporary
>>> tables beforehand?
>>
>> Provide a new pgpool.conf option that tells it to ignore them (with
>> the assumption that they do not exist).
>>
>>>
>>>> I understand if this isn't something you can fix right now, but I'm
>>>> not even getting the impression that you consider this to be a design
>>>> flaw.  A high write volume on the master should never impact the
>>>> response time of any standby/slave with a read query.  This literally
>>>> means that pgpool doesn't scale well in write heavy environments.
>>>
>>> That's why I asked you any idea to solve the problem.
>>
>> I guess I don't understand why pgpool needs to look up the system
>> catalogs on the write server.   Shouldn't they be identical on all
>> servers?
>
> You cannot assume that because streaming replication or slony are
> async replication.
>
> Also remember that temp tables can only be used on primary.

could you create a list of valid tables at startup and periodically poll 
for new tables? if it's an unlogged table you'll know, and if it's a 
temp table (or a very new table) you just wouldn't allow it to be load 
balanced.