I wrote:
> I propose that it'd be a good idea to try to set the stats socket's
> receive buffer size to be a minimum of, say, 100K on all platforms.
> Code for this would be analogous to what we already have in pqcomm.c
> (circa line 760) for forcing up the send buffer size, but SO_RCVBUF
> not SO_SNDBUF.
I experimented with the attached patch. Modern platforms such as
recent Linux and macOS seem to have default receive buffer sizes
in the 100K-200K range. The default is less in older systems, but
even my very oldest dinosaurs will let you set it to at least 256K.
(Don't have Windows to try, though.)
I propose committing this (less the debug logging part) to HEAD
once the beta is out, and then back-patching if it doesn't break
anything and seems to improve matters on frogmouth.
regards, tom lane
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index d4feed1..d868976 100644
*** a/src/backend/postmaster/pgstat.c
--- b/src/backend/postmaster/pgstat.c
***************
*** 93,98 ****
--- 93,101 ----
#define PGSTAT_POLL_LOOP_COUNT (PGSTAT_MAX_WAIT_TIME / PGSTAT_RETRY_DELAY)
#define PGSTAT_INQ_LOOP_COUNT (PGSTAT_INQ_INTERVAL / PGSTAT_RETRY_DELAY)
+ /* Minimum receive buffer size for the collector's socket. */
+ #define PGSTAT_MIN_RCVBUF (100 * 1024)
+
/* ----------
* The initial size hints for the hash tables used in the collector.
*************** retry2:
*** 574,579 ****
--- 577,620 ----
goto startup_failed;
}
+ /*
+ * Try to ensure that the socket's receive buffer is at least
+ * PGSTAT_MIN_RCVBUF bytes, so that it won't easily overflow and lose
+ * data. Use of UDP protocol means that we are willing to lose data under
+ * heavy load, but we don't want it to happen just because of ridiculously
+ * small default buffer sizes (such as 8KB on older Windows versions).
+ */
+ {
+ int old_rcvbuf;
+ int new_rcvbuf;
+ ACCEPT_TYPE_ARG3 rcvbufsize = sizeof(old_rcvbuf);
+
+ if (getsockopt(pgStatSock, SOL_SOCKET, SO_RCVBUF,
+ (char *) &old_rcvbuf, &rcvbufsize) < 0)
+ {
+ elog(LOG, "getsockopt(SO_RCVBUF) failed: %m");
+ /* if we can't get existing size, always try to set it */
+ old_rcvbuf = 0;
+ }
+
+ new_rcvbuf = PGSTAT_MIN_RCVBUF;
+ if (old_rcvbuf < new_rcvbuf)
+ {
+ if (setsockopt(pgStatSock, SOL_SOCKET, SO_RCVBUF,
+ (char *) &new_rcvbuf, sizeof(new_rcvbuf)) < 0)
+ elog(LOG, "setsockopt(SO_RCVBUF) failed: %m");
+ }
+
+ /* this part is just for debugging, not needed at commit: */
+ rcvbufsize = sizeof(new_rcvbuf);
+ if (getsockopt(pgStatSock, SOL_SOCKET, SO_RCVBUF,
+ (char *) &new_rcvbuf, &rcvbufsize) < 0)
+ elog(LOG, "getsockopt(SO_RCVBUF) failed: %m");
+ else
+ elog(LOG, "getsockopt(SO_RCVBUF) was %d, now %d",
+ old_rcvbuf, new_rcvbuf);
+ }
+
pg_freeaddrinfo_all(hints.ai_family, addrs);
return;
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