On Wed, Apr 6, 2016 at 8:11 PM, Fujii Masao <masao.fujii@gmail.com> wrote: > > On Wed, Apr 6, 2016 at 11:14 PM, Amit Kapila <amit.kapila16@gmail.com> wrote: > > On Wed, Apr 6, 2016 at 7:03 PM, Fujii Masao <masao.fujii@gmail.com> wrote: > >> > >> On Wed, Apr 6, 2016 at 8:59 PM, Amit Kapila <amit.kapila16@gmail.com> > >> wrote: > >> > > >> >> BTW, we can move SyncRepUpdateConfig() just after ProcessConfigFile() > >> >> from pg_stat_get_wal_senders() and every backends always parse the > >> >> value > >> >> of s_s_names when the setting is changed. > >> >> > >> > > >> > That sounds appropriate, but not sure what is exact place to call it. > >> > >> Maybe just after the following ProcessConfigFile(). > >> > >> ----------------------------------------- > >> /* > >> * (6) check for any other interesting events that happened while we > >> * slept. > >> */ > >> if (got_SIGHUP) > >> { > >> got_SIGHUP = false; > >> ProcessConfigFile(PGC_SIGHUP); > >> } > >> ----------------------------------------- > >> > >> If we do the move, we also need to either (1) make postmaster call > >> SyncRepUpdateConfig() and pass the parsed result to any forked backends > >> via a file like write_nondefault_variables() does for EXEC_BACKEND > >> environment, or (2) make a backend call SyncRepUpdateConfig() during > >> its initialization phase so that the first call of pg_stat_replication > >> can use the parsed result. (1) seems complicated and overkill. > >> (2) may add very small overhead into the fork of a backend. It would > >> be almost negligible, though. So which logic should we adopt? > >> > > > > Won't it be possible to have assign_* function for synchronous_standby_names > > as we have for some of the other settings like assign_XactIsoLevel and then > > call SyncRepUpdateConfig() in that function? > > It's possible, but still seems to need (1), i.e., the variable that assign_XXX > function assigned needs to be passed to a backend via file for EXEC_BACKEND > environment. >
But for that, I think we don't need to do anything extra. I mean write_nondefault_variables() will automatically write the non-default value of variable and then during backend initialization, it will call read_nondefault_variables which will call set_config_option for non-default parameters and that should set the required value if we have assign_* function defined for the variable.
