On Wed, Jan 22, 2014 at 09:32:09AM -0500, Robert Haas wrote: > On Tue, Jan 21, 2014 at 2:58 PM, Noah Misch <n...@leadboat.com> wrote: > >> What do people prefer? > > > > I recommend performing cleanup on the control segment named in PGShmemHeader > > just before shmdt() in PGSharedMemoryCreate(). No new ERROR or WARNING > > sites > > are necessary. Have dsm_postmaster_startup() continue to perform a cleanup > > on > > the control segment named in the state file. > > I think I'm on board with the first two sentences of this, but after > Fujii Masao's email yesterday, I can't help thinking that what you > propose the third sentence is a bad idea. He cloned a master to > create a standby server on the same machine, and the standby startup > ate the master's dynamic shared memory. We could teach pg_basebackup > not to copy the state file, but that wouldn't help people who take > base backups using the file system copy method, which is a lot of > people.
I agree we should not rely on folks learning to omit the state file from base backups. Abandoning the state file is one way to resolve that, and the reasons I outlined for preferring to keep it were not overriding concerns. We could instead store a postmaster PID in dsm_control_header and only clean if that PID is dead. We could make DSM startup aware of whether we're using a backup label, but that would be awkward thanks to StartupXLOG() happening a good bit later. Yeah, abandoning the state file is looking attractive. -- Noah Misch EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
