pgpool_adm extension

pgpool-II 4.1.5 Documentation
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pgpool_adm is a set of extensions to allow SQL access to Reference II, PCP commands (actually, pcp libraries). It uses foreign data wrapper as shown in the diagram below.

Figure 1. How pgpool_adm works

It is possible to call the functions from either via pgpool-II (1) or via PostgreSQL (2). In case (1), Pgpool-II accepts query from user (1), then forward to PostgreSQL (3). PostgreSQL connects to Pgpool-II (5) and Pgpool-II reply back to PostgreSQL with the result (3). PostgreSQL returns the result to Pgpool-II (5) and Pgpool-II forwards the data to the user (6).

In case (2), PostgreSQL accepts query from user (2). PostgreSQL connects to Pgpool-II (5) and Pgpool-II reply back to PostgreSQL with the result (3). PostgreSQL replies back the data to the user (4).

There are two forms to call pgpool_adm functions: first form accepts Pgpool-II host name (or IP address), pcp port number, pcp user name, its password and another parameters.

In the second form, Pgpool-II server name is required. The server name must be already defined using "CREATE FOREIGN SERVER" command of PostgreSQL . The pcp port number is hard coded as 9898, the pcp user name is assumes to be same as caller's PostgreSQL user name. password is extracted from $HOME/.pcppass.

1. Installing pgpool_adm

pgpool_adm is an extension and should be installed on all PostgreSQL servers.

      $ cd src/sql/pgpool_adm
      $ make
      $ make install

Then issue following SQL command for every database you want to access.

      $ psql ...
      $ CREATE EXTENSION pgpool_adm

Table of Contents
pgpool_adm_pcp_node_info -- a function to display the information on the given node ID
pgpool_adm_pcp_pool_status -- a function to retrieves parameters in pgpool.conf.
pgpool_adm_pcp_node_count -- a function to retrieves number of backend nodes.
pgpool_adm_pcp_attach_node -- a function to attach given node ID
pgpool_adm_pcp_detach_node -- a function to detach given node ID