[pgpool-general: 6834] Re: Using standby pgpool instances

[Tatsuo Ishii]

> Hi all,
> 
> Just another small question: there is a somewhat cryptic remark in the
> documentation regarding the memory_cache_enabled setting (section 5.12.1):
> 
> Note: The query cache is used the relation cache too, if
> enable_shared_relcache is on. You notes that the query cache is used
> regardless memory_cache_enabled parameter, when It is used by relation
> cache. See Section 5.15 for more details to relation cache. 

Thanks for pointing it out. Yeah, we need to rephrase this. Here is my
proposal. What do you think?

------------------------------------------------------------------
Note: The query cache will also be used by shared relation cache if
enable_shared_relcache is set to on. Moreover the query cache is used
even if memory_cache_enabled parameter is set to off. See Section 5.15
for more details on relation cache.
------------------------------------------------------------------

> I do not completely understand what this should mean - I think I will have
> to set enabled_shared_relcache off too?

Actually you don't need to turn off enabled_shared_relcache. Unlike
ordinary query cache, the shared relation cache does not create local
invalidation files. However you might want to set memqcache_expire to
invalidate those cache after some period. Otherwise they will remain
until Pgpool-II restarts.

> Thanks again,
>   Frodo Looijaard
> 
> 
> On Wed, 2020-01-29 at 15:45 +0100, Frodo Looijaard wrote:
>> Hi all,
>> 
>> thanks for you clear answers. I will keep the memory query cache disabled
>> (memory_cache_enabled = off).
>> 
>> Kind regards,
>>   Frodo Looijaard
>> 
>>  
>> On Tue, 2020-01-28 at 21:45 +0900, Tatsuo Ishii wrote:
>> > Hi Frodo,
>> > 
>> > The only thing you need to care in this configuration is in memory
>> > query cache as cache validation mechanism uses local files on each
>> > pgpool node. For example if you have cache validation files for table
>> > A on pgpool1, you need to invalidate (send DML command) by connecting
>> > to pgpool1 aslo. But if you connect to pgpool2 and try to modify table
>> > A, no cache validation will happen since the cache validation file for
>> > table A is not on pgpool2.
>> > 
>> > Other than this, there should be no problem as Usama said.
>> > 
>> > Best regards,
>> > --
>> > Tatsuo Ishii
>> > SRA OSS, Inc. Japan
>> > English: http://www.sraoss.co.jp/index_en.php
>> > Japanese:http://www.sraoss.co.jp
>> > 
>> > > Hi
>> > > The quick answer is you don’t need a virtual-IP if your setup doesn’t need one, and you can connect to standby pgpool without any problem 
>> > > 
>> > > Thanks
>> > > Best regards 
>> > > Muhammad Usama 
>> > > 
>> > > Sent from my iPhone
>> > > 
>> > > > On 27-Jan-2020, at 5:33 PM, Frodo Looijaard <frodo at frodo.looijaard.name> wrote:
>> > > > 
>> > > > Hello,
>> > > > 
>> > > > I am wondering whether we need a floating IP when using multiple pgpool
>> > > > instances with the watchdog (pgpool-II-4.1.0).
>> > > > 
>> > > > It seems you can just connect with a non-master pgpool instance.
>> > > > 
>> > > > Can we expect trouble when we connect to a non-master pgpool node? Can we
>> > > > expect trouble when some connections use the master node and others at the
>> > > > same time use a non-master node, accessing the same Postgres database?
>> > > > 
>> > > > If this can safely be done, we would not need a floating IP; it would
>> > > > suffice to add all pgpool-nodes as alternatives to a JDBC-URL.
>> > > > 
>> > > > If this is not safe, would it not be a nice feature to (perhaps optionally)
>> > > > disable connections to non-master pgpool nodes?
>> > > > 
>> > > > Thanks for your time,
>> > > >  Frodo Looijaard
>> > > > 
>> > > > _______________________________________________
>> > > > pgpool-general mailing list
>> > > > pgpool-general at pgpool.net
>> > > > http://www.pgpool.net/mailman/listinfo/pgpool-general
>> > > _______________________________________________
>> > > pgpool-general mailing list
>> > > pgpool-general at pgpool.net
>> > > http://www.pgpool.net/mailman/listinfo/pgpool-general
>> > _______________________________________________
>> > pgpool-general mailing list
>> > pgpool-general at pgpool.net
>> > http://www.pgpool.net/mailman/listinfo/pgpool-general
>> > 
>> 
>> _______________________________________________
>> pgpool-general mailing list
>> pgpool-general at pgpool.net
>> http://www.pgpool.net/mailman/listinfo/pgpool-general
>> 
> 
> _______________________________________________
> pgpool-general mailing list
> pgpool-general at pgpool.net
> http://www.pgpool.net/mailman/listinfo/pgpool-general