On Fri, Sep 09, 2022 at 12:14:25PM +0530, Bharath Rupireddy wrote: > On Fri, Sep 9, 2022 at 10:57 AM Kyotaro Horiguchi > <horikyota....@gmail.com> wrote: >> At Thu, 8 Sep 2022 10:53:56 -0700, Nathan Bossart <nathandboss...@gmail.com> >> wrote in >> > My general point is that we should probably offer some basic preventative >> > measure against flipping back and forth between streaming and archive >> > recovery while making zero progress. As I noted, maybe that's as simple as >> > having WaitForWALToBecomeAvailable() attempt to restore a file from archive >> > at least once before the new parameter forces us to switch to streaming >> > replication. There might be other ways to handle this. >> >> +1. > > Hm. In that case, I think we can get rid of timeout based switching > mechanism and have this behaviour - the standby can attempt to switch > to streaming mode from archive, say, after fetching 1, 2 or a > configurable number of WAL files. In fact, this is the original idea > proposed by Satya in this thread.
IMO the timeout approach would be more intuitive for users. When it comes to archive recovery, "WAL segment" isn't a standard unit of measure. WAL segment size can differ between clusters, and WAL files can have different amounts of data or take different amounts of time to replay. So I think it would be difficult for the end user to decide on a value. However, even the timeout approach has this sort of problem. If your parameter is set to 1 minute, but the current archive takes 5 minutes to recover, you won't really be testing streaming replication once a minute. That would likely need to be documented. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
