Re: pg_basebackup / recovery

Στις 13/4/23 01:31, ο/η Michael Paquier έγραψε:
> On Wed, Apr 12, 2023 at 01:45:56PM +0300, Achilleas Mantzios - cloud wrote:
>> On 4/12/23 12:32, Fabrice Chapuis wrote:
>>> During recovery process of a self contained backup, how postgres know to
>>> stop reading wal when consistency is reached?
>> Because it knows the full packup info. It will observe the
>>
>> STOP WAL LOCATION: 3BC7/4B000130 (file 0000000200003BC70000004B)
>>
>> inside the backup file
> There is a bit more to that in the recovery logic, depending mostly
> on the presence of backup_ label file in the data folder when recovery
> begins.  Once the backup_label is found at the beginning of recovery,
> its information is stored in the control file and the file is renamed
> to backup_label.old hence stopping the server when recovery has not
> reached its expected point would rely on the control file contents
> later on.  Then, the startup process and its WAL redo makes sure that
> WAL replays until it finds the WAL record marking the end of the
> backup.  Grepping for XLOG_BACKUP_END (WAL record type in this case)
> shows all the areas that rely on that, and xlogrecovery.c covers the
> most relevant bits.

Thank you for the info!

Sorry about my stupid typo "packup" :(

> --
> Michael

-- 
Achilleas Mantzios
  IT DEV - HEAD
  IT DEPT
  Dynacom Tankers Mgmt