[Pgpool-hackers] pgpool limitations

[Gurjeet Singh]

Hi,

    I have configured pgpool 3.0.3 in master/slave mode and setup streaming
replication between the master and the slave systems. I want to be able to
add more slaves to the setup whenever read-only load increases beyond the
current capacity, and remove slave databases when the load subsides.

    I have found the following limitations, and wanted to check with you
guys if these are really true or is it just me that I misconfigured pgpool.

.) Killing one slave Postgres instance (in immediate mode) kills all
connections to the pool, even those connections whose queries are currently
running on a different Postgres instance which is still available.

    In essence a connection loss from a slave backend causes pgpool to
reinitialize itself, hence breaking all existing connections.

.) The commands pcp_attach_node and pcp_detach node cause the pool to
disconnect all connections and reinitialize the pool.

.) Adding a new entries backend_hostname<n> and backend_port<n> to the end
of the current node list in pgpool.conf and reloading the config does add
the new node to pgpool (as documented)l, but the pcp_node_info command shows
that this new node is in 'down' state (code 3) and the docs don't say how to
bring a node from 'down' state to 'up' state (code 1 or 2). Doing
pcp_node_attach does bring it in 'up' mode but as noted above, this command
causes all connections to be disconnected.

    How can I add/remove slave databases to pgpool cleanly without affecting
the connections that are working on other databases.

Thanks,

PS: I am attaching my configuration files for reference.
-- 
Gurjeet Singh
EnterpriseDB Corporation
The Enterprise PostgreSQL Company
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