Re: Time-Delayed Standbys

Hi Fabrízio,

I test your v4 patch, and send your review comments.

* Fix typo
> 49 -# commited transactions from the master, specify a recovery time delay.
> 49 +# committed transactions from the master, specify a recovery time delay.

* Fix white space
> 177 - if (secs <= 0 && microsecs <=0)
> 177 + if (secs <= 0 && microsecs <=0 )

* Add functionality (I propose)
We can set negative number at min_standby_apply_delay. I think that this feature
is for world wide replication situation. For example, master server is in Japan
and slave server is in San Francisco. Japan time fowards than San Francisco time
. And if we want to delay in this situation, it can need negative number in
min_standby_apply_delay. So I propose that time delay conditional branch change
under following.
> - if (min_standby_apply_delay > 0)
> + if (min_standby_apply_delay != 0)
What do you think? It might also be working collectry.

* Problem 1
I read your wittened document. There is "PITR has not affected".
However, when I run PITR with min_standby_apply_delay=3000000, it cannot start
server. The log is under following.
> [mitsu-ko(at)localhost postgresql]$ bin/pg_ctl -D data2 start
> server starting
> [mitsu-ko(at)localhost postgresql]$ LOG: database system was interrupted; last known up at 2013-12-08 18:57:00 JST
> LOG: creating missing WAL directory "pg_xlog/archive_status"
> cp: cannot stat `../arc/00000002.history':
> LOG: starting archive recovery
> LOG: restored log file "000000010000000000000041" from archive
> LOG: redo starts at 0/41000028
> LOG: consistent recovery state reached at 0/410000F0
> LOG: database system is ready to accept read only connections
> LOG: restored log file "000000010000000000000042" from archive
> FATAL: cannot wait on a latch owned by another process
> LOG: startup process (PID 30501) exited with exit code 1
> LOG: terminating any other active server processes
We need recovery flag for controling PITR situation.

That's all for now.
If you are busy, please fix in your pace. I'm busy and I'd like to wait your
time, too:-)

Regards,
--
Mitsumasa KONDO
NTT Open Source Software Center