Thread: pgpool fundamental questions

pgpool fundamental questions

From
"Brian Maguire"
Date:
Pgpool is a real cool project, I really hope it keeps evolving.  I have a couple basic/fundamental questions that I
hopingto get some clarification on.
 

Question 1: If pgpool is used in conjuntion with slony or a another replication it can be used only for its
loadbalancingand failover.  I am correct like this? What else needs to be done to set in failover? 
 

set the backends....

backend_host_name =master
secondary_backend_host_name=slave

set it to lb on and replication off...

load_balance_mode=true
replication_mode=false

set the health checks for failover.

health_check_timeout=20
health_check_period=20
health_check_user=user

Question 2:  In the case that the master goes down pgpool would failover to the slave/secondary.  What would be the
logicalsteps to bring it back to normal.  Can this be down with no downtime with both?
 

1) Turn off health check or weight the weight_master =0  so when you bring the master back load does not go to it when
youbring the db backup.  or does pgpool leave it down automatically until you restart pgpool?
 

2) Shutdown replication on the master.  Bring back the master backup.  

3) rsynch the data from the slave to the master???

4) turn replication?

Question 3: Is there anyway to make pgpool loadbalance certain select queries to the slave such as queries to a
particulartable?  Is that a future feature planned?
 

 

Thanks!

 

 

 


Re: pgpool fundamental questions

From
Tatsuo Ishii
Date:
> Pgpool is a real cool project, I really hope it keeps evolving.  I have a couple basic/fundamental questions that I
hopingto get some clarification on. 
>
> Question 1: If pgpool is used in conjuntion with slony or a another replication it can be used only for its
loadbalancingand failover.  I am correct like this? What else needs to be done to set in failover?  
>
> set the backends....
>
> backend_host_name =master
> secondary_backend_host_name=slave
>
> set it to lb on and replication off...
>
> load_balance_mode=true
> replication_mode=false
>
> set the health checks for failover.
>
> health_check_timeout=20
> health_check_period=20
> health_check_user=user

You need to set master_slave_mode to true.

> Question 2:  In the case that the master goes down pgpool would failover to the slave/secondary.  What would be the
logicalsteps to bring it back to normal.  Can this be down with no downtime with both? 

> 1) Turn off health check or weight the weight_master =0  so when you bring the master back load does not go to it
whenyou bring the db backup.  or does pgpool leave it down automatically until you restart pgpool? 

Yes.

> 2) Shutdown replication on the master.  Bring back the master backup.
>
> 3) rsynch the data from the slave to the master???
>
> 4) turn replication?

It seems these steps OK. But you are going to use Slony-I with pgpool,
no? Then you might want to sync DBs using Slony-I?

> Question 3: Is there anyway to make pgpool loadbalance certain select queries to the slave such as queries to a
particulartable?  Is that a future feature planned? 

Since pgpool does not parse queries, probably it would not happen in
the future. Ideas are welcome how to know a query is accessing
particular table without parsing it.
--
Tatsuo Ishii