Re: Re: [COMMITTERS] pgsql: Make CheckRequiredParameterValues() depend upon correct

On Tue, Apr 27, 2010 at 7:50 PM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>> It's OK in pg_start_backup(), but seems NG in pg_stop_backup() since
>> it waits until some WAL files have been archived by the archiver. No?
>
> Good point, that logic would need to be changed too. Should it simply
> return immediately if archive_mode=off?

What if we wrongly set archive_mode to on and wal_mode to minimal?
I think that checking XLogArchivingActive() in pg_stop_backup() is
adequate.

>>>> + /*
>>>> +  * For Hot Standby, the WAL must be generated with 'hot_standby' mode,
>>>> +  * and we must have at least as many backend slots as the primary.
>>>> +  */
>>>> + if (InArchiveRecovery && XLogRequestRecoveryConnections)
>>>> + {
>>>> +   if (ControlFile->wal_mode < WAL_MODE_HOT_STANDBY)
>>>> +       ereport(ERROR,
>>>> +              (errmsg("recovery connections cannot start because
>>>> wal_mode was not set to 'hot_standby' on the WAL source server")));
>>>>
>>>> This seems to always prevent the server from doing an archive recovery
>>>> since wal_mode is expected to be WAL_MODE_ARCHIVE in that case.
>>> No, it doesn't prevent archive recovery. It only prevents hot standby if
>>> wal_mode was not 'hot_standby' in the master. I think you missed the "&&
>>> XLogRequestRecoveryConnections" condition above.
>>
>> Even if we do only archive recovery, XLogRequestRecoveryConnections
>> might be TRUE. Or we need to ensure that the recovery_connection is
>> FALSE in the postgresql.conf before starting archive recovery?
>
> Umm, yes, if you have recovery_connnections=on, it means you want hot
> standby. And for that you need wal_mode='hot_standby'.

Since the default value of recovery_connections is TRUE, I think that
the trouble which I encountered would often happen. We should disable
recovery_connections by default? Furthermore should move it from
postgresql.conf to recovery.conf?

On the other hand, I feel that recovery_connections=on in an archive
recovery is valid configuration *until* any read only connections are
requested. How about moving the above check to postmaster or backend?

Regards,

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