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

On Tue, Apr 27, 2010 at 7:24 AM, Fujii Masao <masao.fujii@gmail.com> wrote:
> On Tue, Apr 27, 2010 at 7:50 PM, Heikki Linnakangas
> <heikki.linnakangas@enterprisedb.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 it waits until some WAL files have been archived by the archiver.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.

That case should be rejected at primary startup.

>>>>> + /*
>>>>> +  * 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?

Or just not starting recovery connections, but still doing archive
recovery?  I think in this case a WARNING might be adequate.

...Robert