On Thu, Dec 15, 2016 at 10:04 AM, Magnus Hagander <mag...@hagander.net> wrote:
> I've started work on a patch to make pg_basebackup use the temporary slots > feature that has been committed (thanks Petr!!). The reason for this is to > avoid the cases where a burst of traffic on the master during the backup > can cause the receive log part of the basebackup to fall far enough behind > that it fails. > > I have a few considerations at this point, about interaction with existing > options. > > Right now, we have -S/--slot which specifies a slot name. If you want to > use that, you have to create the slot ahead of time, and it will be a > permanent slot (of course). This is primarily documented as a feature to > use for replication (to make sure xlog is kept around until the standby is > started up), but it does also solve the same problem. But to use it for > base backups today you have to manually create the slot, then base backup, > then drop the slot, which is error prone. > > My thought is that if -S/--slot is not specified, but -X stream is, then > we use a temporary slot always. This obviously requires the server to be > configured with enough slots (I still think we should change the default > here, but that's a different topic), but I think that's acceptable. Then we > should add a "--no-slot" to make it revert to previous behaviour. > > Does that seem reasonable? Or would people prefer it to default to off? > > > However, it also made me think that the interface for setting up a replica > with a *permanent* slot would be much nicer if we could just have > pg_basebackup create the slot, instead of having to create it manually. > > Basically, I'm envisioning adding an IF_NOT_EXISTS argument to > CREATE_REPLICATION_SLOT, so that pg_basebackup can pass up the slot name it > wants to use and have it created if necessary. Do people think think this > is worth doing? (It would also make pg_receivexlog and pg_receivelogical > easier to use, I think, and it would obviously be implemented there as > well). > > Pah, nevermind this last question. I was looking a completely broken branch -- we already have the if-not-exists parameter for pg_receivexlog/pg_receivelogical. I shouldn't write emails before thinking... -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
