Re: shared-memory based stats collector

On Fri, Mar 5, 2021 at 8:32 PM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>
wrote:

>
>
> On 2021/03/05 17:18, Kyotaro Horiguchi wrote:
> > At Thu, 21 Jan 2021 12:03:48 +0900 (JST), Kyotaro Horiguchi <
> horikyota(dot)ntt(at)gmail(dot)com> wrote in
> >> Commit 960869da08 (database statistics) conflicted with this. Rebased.
> >>
> >> I'm concerned about the behavior that pgstat_update_connstats calls
> >> GetCurrentTimestamp() every time stats update happens (with intervals
> >> of 10s-60s in this patch). But I didn't change that design since that
> >> happens with about 0.5s intervals in master and the rate is largely
> >> reduced in this patch, to make this patch simpler.
> >
> > I stepped on my foot, and another commit coflicted. Just rebased.
>
> Thanks for rebasing the patches!
>
> I think that 0003 patch is self-contained and useful, for example which
> enables us to monitor archiver process in pg_stat_activity. So IMO
> it's worth pusing 0003 patch firstly.
>
> Here are the review comments for 0003 patch.
>
> + /* Archiver process's latch */
> + Latch *archiverLatch;
> + /* Current shared estimate of appropriate spins_per_delay value */
>
> The last line in the above seems not necessary.
>
> In proc.h, NUM_AUXILIARY_PROCS needs to be incremented.
>
> /* ----------
> * Functions called from postmaster
> * ----------
> */
> extern int pgarch_start(void);
>
> In pgarch.h, the above is not necessary.
>
> +extern void XLogArchiveWakeup(void);
>
> This seems no longer necessary.
>
> +extern void XLogArchiveWakeupStart(void);
> +extern void XLogArchiveWakeupEnd(void);
> +extern void XLogArchiveWakeup(void);
>
> These seem also no longer necessary.
>
> PgArchPID = 0;
> if (!EXIT_STATUS_0(exitstatus))
> - LogChildExit(LOG, _("archiver process"),
> - pid, exitstatus);
> - if (PgArchStartupAllowed())
> - PgArchPID = pgarch_start();
> + HandleChildCrash(pid, exitstatus,
> +
> _("archiver process"));
>
> I don't think that we should treat non-zero exit condition as a crash,
> as before. Otherwise when archive_command fails on a signal,
> archiver emits FATAL error and which leads the server restart.
>
> - * walwriter, autovacuum, or background worker.
> + * walwriter, autovacuum, archiver or background worker.
> *
> * The objectives here are to clean up our local state about the child
> * process, and to signal all other remaining children to quickdie.
> @@ -3609,6 +3606,18 @@ HandleChildCrash(int pid, int exitstatus, const
> char *procname)
> signal_child(AutoVacPID, (SendStop ? SIGSTOP : SIGQUIT));
> }
>
> + /* Take care of the archiver too */
> + if (pid == PgArchPID)
> + PgArchPID = 0;
> + else if (PgArchPID != 0 && take_action)
> + {
> + ereport(DEBUG2,
> + (errmsg_internal("sending %s to process
> %d",
> + (SendStop
> ? "SIGSTOP" : "SIGQUIT"),
> + (int)
> PgArchPID)));
> + signal_child(PgArchPID, (SendStop ? SIGSTOP : SIGQUIT));
> + }
> +
>
> Same as above.
>
>
> In xlogarchive.c, "#include "storage/pmsignal.h"" is no longer necessary.
>
>
> pgarch_forkexec() should be removed from pgarch.c because it's no longer
> used.
>
>
> /* ------------------------------------------------------------
> * Public functions called from postmaster follow
> * ------------------------------------------------------------
> */
>
> The definition of PgArchiverMain() should be placed just
> after the above comment.
>
>
> exit(0) in PgArchiverMain() should be proc_exit(0)?
>
> Regards,
>
> --
> Fujii Masao
> Advanced Computing Technology Center
> Research and Development Headquarters
> NTT DATA CORPORATION
>
>
>
The code does not compile and has compilation warnings and errors.

------
pgstat.c:446:25: note: ‘cached_slrustats’ declared here
static PgStat_SLRUStats cached_slrustats;
^~~~~~~~~~~~~~~~
guc.c:4372:4: error: use of undeclared identifier 'pgstat_temp_directory';
did you mean 'pgstat_stat_directory'?
&pgstat_temp_directory,
^~~~~~~~~~~~~~~~~~~~~
pgstat_stat_directory
../../../../src/include/pgstat.h:922:14: note: 'pgstat_stat_directory'
declared here
extern char *pgstat_stat_directory;
^
guc.c:4373:3: error: use of undeclared identifier 'PG_STAT_TMP_DIR'
PG_STAT_TMP_DIR,
^
guc.c:4374:25: error: use of undeclared identifier
'assign_pgstat_temp_directory'
check_canonical_path, assign_pgstat_temp_directory, NULL

-------

Can we get an updated patch?

I am marking the patch "Waiting on Author"

--
Ibrar Ahmed