Re: Stefan's bug (was: max_standby_delay considered harmful)

On Tue, May 18, 2010 at 2:26 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Tue, 2010-05-18 at 12:02 +0900, Fujii Masao wrote:
>> On Mon, May 17, 2010 at 9:01 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> >> (1)
>> >> Smart or fast shutdown requested in PM_STARTUP state always removes
>> >> the backup_label file if it exists. But it might be still required
>> >> for subsequent recovery. I changed your patch so that additionally
>> >> the postmaster skips deleting the backup_label in that case.
>> >
>> > Don't like the name NeedBackupLabel seems too specific. That really
>> > corresponds to "we were in recovery". We should have a couple of
>> > super-states that correspond to am in recovery/am not in recovery so we
>> > can drive it from that.
>>
>> ISTM that we can use XLogCtl->SharedRecoveryInProgress for that.
>> Is this OK?
>
> That can change state at any time. Would that work?

Yes. XLogCtl->SharedRecoveryInProgress is set to TRUE only when
XLogCtl structure is initialized (i.e., XLOGShmemInit), and it's
set to FALSE only at the end of recovery.

Here is the updated patch (fix_smart_shutdown_in_recovery_v3_fujii.patch).
I used XLogCtl->SharedRecoveryInProgress instead of NeedBackupLabel,
which made the patch very simple. And I prevented the postmaster
from invoking walreceiver after shutdown or recovery.

>> (2)
>> pg_ctl -ms stop emits the following warning whenever there is the
>> backup_label file in $PGDATA.
>>
>> WARNING: online backup mode is active
>> Shutdown will not complete until pg_stop_backup() is called.
>>
>> This warning doesn't fit in with the shutdown during recovery case.
>> Since smart shutdown might be requested by other than pg_ctl, the
>> warning should be emitted in server side rather than client, I think.
>> How about moving the warning to the server side?

Though I'm not sure if this should be fixed for 9.0, I attached the
patch (move_bkp_cancel_warning_v1.patch).

Regards,

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