Monday, December 19, 2011

Postgresql - pgpool + streaming replication

I'm following this guide to set up a simple pgpool deployment with streaming replication:
http://pgpool.projects.postgresql.org/contrib_docs/simple_sr_setting/

+ the apache2 user process is called wwwrun in opensuse 12.1 ( don't know whether this is also true for other distributions)
+ the apache directory is located in /svr/www/htdocs

+ to enable the apache service you'll need to issue a systemctl
systemctl enable apache2.service
systemctl start apache2.service

+ in order for pgpooladmin to run, it's necessary to grant the wwwrun process user with the appropriate permissions over the underlying pgpool configuration files.

+ gotcha: specifying the health check user is necessary for pgpool to detect which server is master and which slave (whilst in streaming replication).

+ parallel query applies when you partition your tables over several nodes .

Questions:
Apparently pgpool determines which sql statements are dml (which are directed to the master ) and which are only dql (data query language ) which may be balanced. Obviously database permission subsists. pgpool acts as if were another client.

related links.
http://www.howtoforge.com/how-to-set-up-a-postgresql-9.0-hot-standby-streaming-replication-server-with-repmgr-on-opensuse-11.4

http://pgpool.projects.postgresql.org/pgpoolAdmin/doc/en/install.html

http://pgpool.projects.postgresql.org/pgpool-II/doc/pgpool-en.html

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