[pgpool-general: 1070] Re: load balancing

Tatsuo Ishii ishii at postgresql.org
Wed Oct 3 23:24:10 JST 2012


> I have enabled load balancing in pgpool config. when I am inserting it
> writes to both backend but when I query it seem it query only one backend.
> Am I missing something ?
> 
> Oct  3 13:41:23 pgpool pgpool[1532]: DB node id: 1 backend pid: 10489
> statement: SELECT TYPNAME FROM PG_TYPE WHERE OID=1043
> Oct  3 13:41:23 pgpool pgpool[1532]: DB node id: 1 backend pid: 10489
> statement: SELECT TYPNAME FROM PG_TYPE WHERE OID=1043
> Oct  3 13:41:23 pgpool pgpool[1532]: DB node id: 1 backend pid: 10489
> statement: SELECT TYPNAME FROM PG_TYPE WHERE OID=1043
> Oct  3 13:41:23 pgpool pgpool[1532]: DB node id: 1 backend pid: 10489
> statement: SELECT TYPNAME FROM PG_TYPE WHERE OID=23
> Oct  3 13:41:23 pgpool pgpool[1532]: DB node id: 1 backend pid: 10489
> statement: SELECT TYPNAME FROM PG_TYPE WHERE OID=1043
> 
> 
> Does anybody has similar issue ?

Pgpool's load balancing is "session base", not "statement base". That
means, selected load balance node (in your case id 1) is not changed
until session ends. Next session may or may not choose backend id 1
again, because the choice is based on random(). The possibility can be
controlled by "weight" parameter. See FAQ 1.5 also.
http://www.pgpool.net/mediawiki/index.php/FAQ#It_seems_my_pgpool-II_does_not_do_load_balancing._Why.3F
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp


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