Thanks for taking a look! On Thu, Apr 14, 2022 at 11:36:11AM +0900, Kyotaro Horiguchi wrote: > At Wed, 13 Apr 2022 14:35:21 -0700, Nathan Bossart <nathandboss...@gmail.com> > wrote in >> I initially set out to see if it was possible to automatically adjust these >> parameters on a standby, but that is considerably more difficult. It isn't >> enough to just hook into the restart_after_crash functionality since it >> doesn't go back far enough in the postmaster logic. IIUC we'd need to >> reload preloaded libraries (which there is presently no support for), >> recalculate MaxBackends, etc. Another option I considered was to > > Sure. > >> automatically adjust the parameters during startup so that you just need to >> restart the server. However, we need to know for sure that the server is >> going to be a hot standby, and I don't believe we have that information >> where such GUC changes would need to occur (I could be wrong about this). > > Conldn't we use AlterSystemSetConfigFile for this purpose in > CheckRequiredParameterValues?
That's an interesting idea. When an incompatible parameter change is detected, the server would automatically run the equivalent of an ALTER SYSTEM SET command before shutting down or pausing replay. I might draft up a proof-of-concept to see what this looks like and how well it works. >> Anyway, for now I'm just proposing the modest change described above, but >> I'd welcome any discussion about improving matters further in this area. >> >> [0] >> https://postgr.es/m/4ad69a4c-cc9b-0dfe-0352-8b1b0cd36c7b%402ndquadrant.com > > Is the reason for the enum the extensibility to add a new choice like > "auto-adjust"? Yes. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
