On Mon, May 17, 2010 at 7:44 AM, Fujii Masao <masao.fu...@gmail.com> wrote: > On Mon, May 17, 2010 at 8:02 PM, Robert Haas <robertmh...@gmail.com> wrote: >>> (1) >>> Smart or fast shutdown requested in PM_STARTUP state always removes >>> the backup_label file if it exists. But it might be still required >>> for subsequent recovery. I changed your patch so that additionally >>> the postmaster skips deleting the backup_label in that case. >> >> Can you explain in a little more detail how this can cause a problem? >> I'm not very familiar with how the backup label is used. >> >> Also, why is this different in PM_STARTUP than in PM_RECOVERY? >> PM_RECOVERY doesn't guarantee that we've reached consistency. > > Before the startup process sends the PMSIGNAL_RECOVERY_STARTED signal > (i.e., when the postmaster is in PM_STARTUP state), it reads the > backup_label file to know the recovery starting WAL location, saves > that information in pg_control file, and rename the file "backup_label" > to "backup_label.old". > > If the backup_label file is removed before pg_control is updated, > subsequent recovery cannot get the right recovery starting location. > This is the problem that I'm concerned. > > The smart shutdown during recovery and the fast shutdown might call > CancelBackup() and remove the backup_label file. So if shutdown is > requested in PM_STARTUP state, the problem would happen.
OK, I think I understand now. But, the SIGTERM sent by the postmaster doesn't kill the recovery process unconditionally. It will invoke StartupProcShutdownHandler(), which will set set shutdown_requested = true. That gets checked by RestoreArchivedFile() and HandleStartupProcInterrupts(), and I think that neither of those can get invoked until after the control file has been updated. Do you see a way it can happen? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise Postgres Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
