Streaming replication, and walsender during recovery

Hi,

When I configured a cascaded standby (i.e, made the additional
standby server connect to the standby), I got the following
errors, and a cascaded standby didn't start replication.

  ERROR:  timeline 0 of the primary does not match recovery target timeline 1

I didn't care about that case so far. To avoid a confusing error
message, we should forbid a startup of walsender during recovery,
and emit a suitable message? Or support such cascade-configuration?
Though I don't think that the latter is difficult to be implemented,
ISTM it's not the time to do that now.

Thought?

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center