On Mon, Jun 15, 2020 at 03:19:29PM +0200, Laurenz Albe wrote: ! On Mon, 2020-06-15 at 14:50 +0200, Peter wrote: ! > ! An example: ! > ! ! > ! - Backup #1 calls "pgpre.sh" ! > ! - Backup #1 starts copying files ! > ! - Backup #2 calls "pgpre.sh". ! > ! This will cancel the first backup. ! > ! - Backup #1 completes copying files. ! > ! - Backup #1 calls "pgpost.sh". ! > ! It will receive an error. ! > ! So it has to invalidate the backup. ! > ! - Backup #2 completes copying files. ! > ! - Backup #2 calls "pgpost.sh". ! > ! It gets a "backup_label" file and completes the backup. ! > ! > That's not true. ! ! Ah, yes, you are right. Thank You. ! Since "pgpre.sh" and "pgpost.sh" are independent, there ! is no way to tell which of them belongs to which other. Correct. ! So calling "pgpost.sh" indeed ends the most recently started ! backup and returns "backup_label" accordingly. ! ! That means: the caller of the scripts has to make sure ! not to start a second backup while the first one is running. Never run two backups in parallel with such an approach, exactly. And that is one of a couple of likely pitfalls I perceived when looking at that new API. We could fix that, but that will then get more complicated - and people will usually not do that. And that's why I consider that new API as rather dangerous. cheerio, PMc
