2018-06-01 9:00 GMT-03:00 Michael Paquier <mich...@paquier.xyz>: > On Thu, May 31, 2018 at 10:59:04PM -0400, Robert Haas wrote: >> On Wed, May 30, 2018 at 2:00 PM, Michael Paquier <mich...@paquier.xyz> wrote: >>> Hm. There could be an argument for improving the user experience here >>> so as some cleanup is at least attempted except if --no-clean is defined >>> by the caller when --create-slot is used. Do we want an open item for >>> this issue? >> >> Sounds like new development to me. This isn't a bug. > > Still, it seems to me that the user experience is a bit horrible with > this new interface of pg_basebackup. If --create-slot is used, then a > slot is created before starting a backup. If the slot already exists, > then pg_basebackup complains and exits. In order to drop the slot with > a only user who has replication access rights (because nobody is really > going to have a user who has SQL access so as the slot is dropped), then > the only simple way is to use pg_receivewal --drop-slot, making the > whole flow inconsistent. pg_basebackup is usually in server-side > packages, and pg_receivewal is on the client side. The server packages > requiring the client packages, then we are sure that pg_basebackup will > drag in pg_receivewal. > Debian and derivatives put pg_basebackup in the client package (indeed, it a client program). A possible fix is to drop the slot if there is an error. However, if the problem is connectivity, we can't drop it. In this case, we can print a user-friendly error saying that the user should drop that slot before try again). If we follow this idea, then I consider it to be a bug fix.
> Still, shouldn't there be a --drop-slot option in pg_basebackup? In > this case, if --drop-slot is used, then the slot is dropped and > pg_basebackup exits immediately. > I don't like it. You should send an extra command to recover from an error. It also does not follow the idempotent behavior. I know that you are trying to mimic pg_receivewal options but I prefer another option that removes the slot if it exists (say, --drop-slot-if-exists). In this case, I consider this option as new development. -- Euler Taveira Timbira - http://www.timbira.com.br/ PostgreSQL: Consultoria, Desenvolvimento, Suporte 24x7 e Treinamento
