postgres_fdw: Fix bug in connection status check.

MasaoFujii · MasaoFujii · commit 454aab4b738e · 2024-07-27T03:58:48.000+09:00
The buildfarm member "hake" reported a failure in the regression test added by commit 857df3c, where postgres_fdw_get_connections(true) returned unexpected results. The function postgres_fdw_get_connections(true) checks if a connection is closed by using POLLRDHUP in the requested events and calling poll(). Previously, the function only considered POLLRDHUP or 0 as valid returned events. However, poll() can also return POLLHUP, POLLERR, and/or POLLNVAL. So if any of these events were returned, postgres_fdw_get_connections(true) would report incorrect results. postgres_fdw_get_connections(true) failed to account for these return events. This commit updates postgres_fdw_get_connections(true) to correctly report a closed connection when poll() returns not only POLLRDHUP but also POLLHUP, POLLERR, or POLLNVAL. Discussion: https://postgr.es/m/fd8f6186-9e1e-4b9a-92c5-e71e3697d381@oss.nttdata.com
diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c
@@ -2309,7 +2309,8 @@ pgfdw_conn_check(PGconn *conn)
 		if (result < 0)
 			return -1;
 
-		return (input_fd.revents & POLLRDHUP) ? 1 : 0;
+		return (input_fd.revents &
+				(POLLRDHUP | POLLHUP | POLLERR | POLLNVAL)) ? 1 : 0;
 	}
 #else
 	return 0;

Original file line number	Diff line number	Diff line change
`@@ -2309,7 +2309,8 @@ pgfdw_conn_check(PGconn *conn)`
`2309`	`2309`	`if (result < 0)`
`2310`	`2310`	`return -1;`
`2311`	`2311`
`2312`		`- return (input_fd.revents & POLLRDHUP) ? 1 : 0;`
	`2312`	`+ return (input_fd.revents &`
	`2313`	`+ (POLLRDHUP \| POLLHUP \| POLLERR \| POLLNVAL)) ? 1 : 0;`
`2313`	`2314`	`}`
`2314`	`2315`	`#else`
`2315`	`2316`	`return 0;`