[pgpool-general: 1385] Re: PgPool 3.2.2 doesn't appear to be load balancing

[David Kerr]

which reminds me, is there a way to do that w/o restarting the server with -D?

On Feb 11, 2013, at 5:17 PM, web at mr-paradox.net wrote:

> Looks like I had to clear the node status, pgpool thought that my slave node was 
> down.
> 
> On Mon, Feb 11, 2013 at 03:13:29PM -0800, web at mr-paradox.net wrote:
> - pgpool-II version 3.2.2 (namameboshi), CentOS
> - 
> - My configuration is currently like this
> - master_slave_mode = on             # (change requires restart)
> - master_slave_sub_mode = 'stream'   # (change requires restart)
> - 
> - sr_check_period = 10
> - sr_check_user = 'nobody'
> - sr_check_password = 'n0b0dy'
> - delay_threshold = 10000000
> - 
> - backend_hostname0 = master
> - backend_port0 = 5432
> - backend_weight0 = 0
> - backend_data_directory0 = '/db/pg'
> - backend_flag0 = 'ALLOW_TO_FAILOVER'
> - 
> - backend_hostname1 = slave
> - backend_port1 = 5432
> - backend_weight1 = 1
> - backend_data_directory1 = '/db/pg'
> - backend_flag1 = 'ALLOW_TO_FAILOVER'
> - 
> - All reads and writes are currently going to the master.
> - 
> - load_balance_mode = on
> - ignore_leading_white_space = on
> - white_function_list = ''
> - black_function_list = 'currval,lastval,nextval,setval'
> - 
> - I've read the FAQ:
> - 
> - > It seems my pgpool-II does not do load balancing. Why?
> - > First of all, pgpool-II' load balancing is "session base", not "statement base". That means, DB node
> - > selection for load balancing is decided at the beginning of session. So all SQL statements are sent to the
> - > same DB node until the session ends.
> - 
> - To mitigate this I have a low client_idle_limit, since rails will attempt to retain it's own pool.
> - I'd love an opinion on this.
> - 
> - > Another point is, whether statement is in an explicit transaction or not. If the statement is in a
> - > transaction, it will not be load balanced in the replication mode. In pgpool-II 3.0 or later, SELECT will be
> - > load balanced even in a transaction if operated in the master/slave mode.
> - 
> - I read this as: in version >3 that I should expect to see SELECTs load balanced in master/slave mode.
> - 
> - > Note the method to choose DB node is not LRU or some such. Pgpool-II chooses DB node randomly considering
> - > the "weight" parameter in pgpool.conf. This means that the chosen DB node is not uniformly distributed among
> - > DB nodes in short term. You might want to inspect the effect of load balancing after ~100 queries have been
> - > sent.
> - 
> - I set the weight for the master to 0 in hopes that basically all non-writes go to the slave.
> - 
> - 
> - Any help would be great, if i can debug, or log anything I'd be happy to do so. (nothing particularly
> - useful is in the current logs)
> - 
> - Thanks
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