Beware, the echo command always returns the same exit status, whether the archiving had succeeded or not. You might lose WAL files!
Regarding the restore command: It will be executed only if the slave is not capable of receiving all WALs via streaming replication, e. g. in case the slave was of for a while. Regards, Holger Am 31. Juli 2019 11:28:44 MESZ schrieb Mariel Cherkassky <mariel.cherkas...@gmail.com>: >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 will be 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 was launched"' > >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_sender and wal receiver. I >dont see in my logs in the secondary that the restore_command is used >but I >see that the same wal files as in the primary are exists on the pg_xlog >in >the secondary. Does the streaming replication generates wals on the >secondary from the wals records that it receives from the primary ? -- Holger Jakobs, Bergisch Gladbach +49 178 9759012 - sent from mobile, therefore short -
