Failing backups, canceling statement due to conflict with recovery

Hi.

I'm unable to offload my backups to one of my PG 9.1 hot standbys
using purely streaming replication. After a few hours, usually on the
same large table, pg_dump is failing with 'ERROR: canceling statement
due to conflict with recovery'.

From my reading from the documentation, this should not be possible as
my hot standby has 'hot_standby_feedback = on' in its postgresql.conf.

I submitted a bug report a while ago, but am still unsure if this
option has never worked as intended or if I'm misinterpreting the
documentation.

My goal is to reliably make pg_dump backups from a hot standby without
the hot standby lagging far behind the master.

--
Stuart Bishop <stuart(at)stuartbishop(dot)net>
http://www.stuartbishop.net/