I currently have a slave02 server that is replicating from another slave01 via Cascading replication. The master01 server is shipping wal_files (via ssh) to both slaves.
I'm doing some tests on slave02 to test the recovery via wal_files... The goal here is to stop postgres, wait few minutes, start postgres again, watch it recovering from wal_files, once it's done see the streaming replication start working again.
1 - Stop postgres on slave02(streaming replication + wal_files)
2 - Wait for 5 minutes
3 - Start postgres - The goal here is to tail the logs to see if the wal_files are being successfully recovered
However, when doing step3 I get these messages:
cp: cannot stat '/walfiles/0000000200001AF8000000A4': No such file or directory
cp: cannot stat '/walfiles/0000000200001AF8000000A5': No such file or directory
cp: cannot stat '/walfiles/0000000200001AF8000000A6': No such file or directory
LOG: consistent recovery state reached at 1AF8/AB629F90
LOG: database system is ready to accept read only connections
LOG: streaming replication successfully connected to primary
still on slave01: Sometimes the log_delay time is bigger.. sometimes is lower
SELECT CASE WHEN pg_last_xlog_receive_location() = pg_last_xlog_replay_location() THEN 0 ELSE EXTRACT (EPOCH FROM now() - pg_last_xact_replay_timestamp()) END AS log_delay;
log_delay
-----------
0.386863
On master01:
select * from pg_current_xlog_location();
pg_current_xlog_location
--------------------------
1AF8/D3F47A80
QUESTION:
So.. I just wanna understand what's the risk of those errors... what's happening?
cp: cannot stat '/walfiles/0000000200001AF8000000A5': No such file or directory - Means it didn't find the file. However, the file exists on the Master, but it didn't start shipping yet. What are the consequences of that?
That is just saying that the slave cannot find the WAL file. That should not be of big importance. Eventually, that will vanish when the log file gets shipped from the master. Also "cp: cannot stat." errors have been been fixed in 9.3 i believe.
Hi Venkata !
Yeah that's fine.. the streaming replication is already working fine.
But, as it didn't find/recover some of the wal_files, doesn't that mean that the DB isn't up-to-date?
Otherwise what's the purpose of the wal_files if not be responsible to contain the essential data to the DB be up-to-date?
