Re: Missing WALs when doing pg_basebackup from slave...

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От Venkata Balaji N
Тема Re: Missing WALs when doing pg_basebackup from slave...
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Msg-id CAEyp7J98N0_UNJURr2kM-kTfHGRf1EhynaUHQjOuwkDwNW-FRw@mail.gmail.com
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Ответ на Missing WALs when doing pg_basebackup from slave...  (<marin@kset.org>)
Ответы Re: Missing WALs when doing pg_basebackup from slave...  (<marin@kset.org>)
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On Wed, Jun 10, 2015 at 6:47 PM, <marin@kset.org> wrote:

Is it normal that pg_basebackup runs successfully (rc=0) and there is no
WAL files present?

Yes, it is normal. "pg_basebackup" ensures that required WALs are backed along with the data directory. This is to ensure backup is consistent.
 
The master and slave are sitting idle, after only a few transaction on the
master at the beginning of the day. I noted that all WAL switches are
caused by the backup running on the master. Is it possible the slave is in
a consistent state when it has applied all changes from the previous WAL
and the new WAL hasn't been created yet on the master (so actually no WAL-s
are needed to restore it to a consistent state)?
 
I am not sure if I got your question correct. The amount of transactions in the master database may be low or high, the WALs will be replicated to slave.
To ensure slave is receiving all the WALs, you need to check the sync status between master and slave. If there is no new WAL generated at master, then slave must be in consistent state should have applied all the previous WALs, if not, then all the previous WALs are needed to get the slave to a consistent state. Nothing can be advised straight without knowing your replication configuration/architecture details.

Regards,
Venkata Balaji N

Fujitsu Australia



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