On Mon, 2009-04-13 at 14:52 +0900, Fujii Masao wrote: > A lookahead (the +1) may have pg_standby get stuck as follows. > Am I missing something? > > 1. the trigger file containing "smart" is created. > 2. pg_standby is executed. > 2-1. nextWALfile is restored. > 2-2. the trigger file is deleted because nextWALfile+1 doesn't exist. > 3. the restored nextWALfile is applied. > 4. pg_standby is executed again to restore nextWALfile+1.
This can't happen. (4) will never occur when (2-2) has occurred. A non-zero error code means file not available which will cause recovery to end and hence no requests for further WAL files are made. It does *seem* as if there is a race condition there in that another WAL file may arrive after we have taken the decision there are no more WAL files, but it's not a problem. That could happen if we issue the trigger while the master is still up, which is a mistake - why would we do that? If we only issue the trigger once we are happy the master is down then we don't get a problem. So lets do it the next+1 way, when triggered. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
