WAL archive on slave - Mailing list pgsql-general

From James Sewell
Subject WAL archive on slave
Date
Msg-id CANkGpBuD4xDW+gFLA7a-=i03-XT2uwtJQbsmFa=nGWMeTWhvgA@mail.gmail.com
Whole thread Raw
Responses Re: WAL archive on slave  (Albe Laurenz <laurenz.albe@wien.gv.at>)
List pgsql-general
Hello,

My understanding is that WAL archiving can not be enabled on the slave in a streaming replication pair.

If this is correct, is there a reason behind it? I can see logs showing up in pg_xlog, so could they not be archived?

The reason I ask is if this happened it would allow the following with a streaming replication pair (A,B):

  1. Start A as master
  2. Attach B as slave using basebackup
  3. work ....
  4. Promote B to master
  5. Restore A from a scheduled backup to a time before promotion
  6. Attach A as slave pointing at B's WAL archive 
If we used A's WAL archive in this case and A had writes after the promotion then we would get timeline errors.

As far as I can tell, using the WAL archive from B would resolve this issue.

Or have I missed something here?

Cheers,


Cheers,

James Sewell,
PostgreSQL Team Lead / Solutions Architect
______________________________________
 

Level 2, 50 Queen St, Melbourne VIC 3000

(+61) 3 8370 8000  W www.lisasoft.com  (+61) 3 8370 8099
 


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