Re: A question regarding streaming replication - Mailing list pgsql-admin

From Fabio Pardi
Subject Re: A question regarding streaming replication
Date
Msg-id b3c08032-f1b8-0e89-8e12-8ca22ada54ff@portavita.eu
Whole thread Raw
List pgsql-admin
Hi Mariel,

please, as already you have been told already in other occasions, do not cross-post. 

Posting to 2 mailing lists will disperse the answers, duplicate the efforts and probably waste time that might go into
helpingsomebody else. 
 

Same reason why not to call 2 ambulances when somebody does not feel good.

regards,

fabio pardi


On 31/07/2019 11:28, Mariel Cherkassky wrote:
> Hey all,
> I have a  questions regarding streaming replication that I would like to ask in order to understand the feature
better: 
 
> I have 2 nodes configured with replication (primary + secondary).
> In my primary I configured streaming replcation + archiving. My archive command : 
> gzip < %p > /var/lib/pgsql/archive/%f ; echo "archiving wal %f"
> 
> Correct me if I'm wrong but my archive_command will be run when the archive_timeout is reached or when the wal is
full(16MB). The wal file is created with default size of 16MB and it will be archived only after 16MB of wal records
willbe created.
 
> 
> In my secondary I have the following settings : 
> restore_command = 'rsync -avzhe ssh postgres@my_primary :/var/lib/pgsql/archive/%f /var/lib/pgsql/archive/%f ; gunzip
</var/lib/pgsql/archive/%f > %p; echo "restore command was launched"'
 
> archive_cleanup_command = '/usr/pgsql-9.6/bin/pg_archivecleanup /var/lib/pgsql/archive %r; "archive_cleanupup for %r
waslaunched"'
 
> 
> Which means, that the restore command on the secondary connects to the primary, copies the wal file from the archive
dir, unzip it and saves it in the pg_xlog dir of the database.
 
> 
> my question : 
> When exactly the restore_command will be used ? I use streaming replication therefore wal records are passed through
wal_senderand wal receiver. I dont see in my logs in the secondary that the restore_command is used but I see that the
samewal files as in the primary are exists on the pg_xlog in the secondary. Does the streaming replication generates
walson the secondary from the wals records that it receives from the primary ?
 
> 
> 



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