Hot Standby Lagging Behind

Hi Everyone,

I have some questions about the PostgreSQL streaming replication feature. I
have been able to setup a hot-standby server, and I can see updates on the
master server being replayed on the standby server.

However I notice that once I start making read-only queries, the standby
starts lagging behind the master server. After a while, the delay can reach
over 1 minute, even though I set the max_standby_streaming_delay parameter
to 15s. I am under the impression that once a WAL record is lagging 15s
behind, then it should trump any read-only queries in the system.

Below are the values of pg_last_xlog_receive_location and
pg_last_xlog_replay_location at several time points

now 03:06:16
pg_last_xlog_receive_location 0/59A31620
pg_last_xlog_replay_location 0/599A6B90

now 03:07:18
pg_last_xlog_receive_location 0/59A98460
pg_last_xlog_replay_location 0/59A1BE58

now 03:07:31
pg_last_xlog_receive_location 0/59AA8F48
pg_last_xlog_replay_location 0/59A22288

So as we can see the WAL record at 0/59A31620 was received at 03:06:16, but
more than a minute later at 03:07:31, it still hasn't been replayed.

Am I configuring the wrong thing? Is there an option to increase the
priority of the WAL replay once it has been lagging for a certain amount of
WAL record?

Thanks in advance for your help.

Prima