Use WL_SOCKET_CLOSED for client_connection_check_interval.

Previously we used poll() directly to check for a POLLRDHUP event.
Instead, use the WaitEventSet API to poll the socket for
WL_SOCKET_CLOSED, which knows how to detect this condition on many more
operating systems.

Reviewed-by: Zhihong Yu <[email protected]>
Reviewed-by: Maksim Milyutin <[email protected]>
Reviewed-by: Andres Freund <[email protected]>
Discussion: https://postgr.es/m/77def86b27e41f0efcba411460e929ae%40postgrespro.ru

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index fc63172efde3070579f995bad4cd7046da26cea9..53b361e7a92de0ebb3c93f1e54d163bf7f2455d5 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1012,9 +1012,9 @@ include_dir 'conf.d'
         the kernel reports that the connection is closed.
        </para>
        <para>
-        This option is currently available only on systems that support the
-        non-standard <symbol>POLLRDHUP</symbol> extension to the
-        <symbol>poll</symbol> system call, including Linux.
+        This option relies on kernel events exposed by Linux, macOS, illumos
+        and the BSD family of operating systems, and is not currently available
+        on other systems.
        </para>
        <para>
         If the value is specified without units, it is taken as milliseconds.

diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index 22eb04948ecd1a9c2facbad7eabaa53a0c02c0aa..9e34f616debc4ec4236bf60ab603eb51bf771343 100644 (file)
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -204,7 +204,7 @@ pq_init(void)
                (errmsg("could not set socket to nonblocking mode: %m")));
 #endif
 
-   FeBeWaitSet = CreateWaitEventSet(TopMemoryContext, 3);
+   FeBeWaitSet = CreateWaitEventSet(TopMemoryContext, FeBeWaitSetNEvents);
    socket_pos = AddWaitEventToSet(FeBeWaitSet, WL_SOCKET_WRITEABLE,
                                   MyProcPort->sock, NULL, NULL);
    latch_pos = AddWaitEventToSet(FeBeWaitSet, WL_LATCH_SET, PGINVALID_SOCKET,
@@ -1960,33 +1960,33 @@ pq_settcpusertimeout(int timeout, Port *port)
 bool
 pq_check_connection(void)
 {
-#if defined(POLLRDHUP)
-   /*
-    * POLLRDHUP is a Linux extension to poll(2) to detect sockets closed by
-    * the other end.  We don't have a portable way to do that without
-    * actually trying to read or write data on other systems.  We don't want
-    * to read because that would be confused by pipelined queries and COPY
-    * data. Perhaps in future we'll try to write a heartbeat message instead.
-    */
-   struct pollfd pollfd;
+   WaitEvent   events[FeBeWaitSetNEvents];
    int         rc;
 
-   pollfd.fd = MyProcPort->sock;
-   pollfd.events = POLLOUT | POLLIN | POLLRDHUP;
-   pollfd.revents = 0;
-
-   rc = poll(&pollfd, 1, 0);
+   /*
+    * It's OK to modify the socket event filter without restoring, because
+    * all FeBeWaitSet socket wait sites do the same.
+    */
+   ModifyWaitEvent(FeBeWaitSet, FeBeWaitSetSocketPos, WL_SOCKET_CLOSED, NULL);
 
-   if (rc < 0)
+retry:
+   rc = WaitEventSetWait(FeBeWaitSet, 0, events, lengthof(events), 0);
+   for (int i = 0; i < rc; ++i)
    {
-       ereport(COMMERROR,
-               (errcode_for_socket_access(),
-                errmsg("could not poll socket: %m")));
-       return false;
+       if (events[i].events & WL_SOCKET_CLOSED)
+           return false;
+       if (events[i].events & WL_LATCH_SET)
+       {
+           /*
+            * A latch event might be preventing other events from being
+            * reported.  Reset it and poll again.  No need to restore it
+            * because no code should expect latches to survive across
+            * CHECK_FOR_INTERRUPTS().
+            */
+            ResetLatch(MyLatch);
+            goto retry;
+       }
    }
-   else if (rc == 1 && (pollfd.revents & (POLLHUP | POLLRDHUP)))
-       return false;
-#endif
 
    return true;
 }

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f505413a7f96f065cea6d1620e36d4f8e6bf5920..e2fe219aa82be5bbf4c1d5c03a21c64717ecee8e 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -12192,14 +12192,11 @@ check_huge_page_size(int *newval, void **extra, GucSource source)
 static bool
 check_client_connection_check_interval(int *newval, void **extra, GucSource source)
 {
-#ifndef POLLRDHUP
-   /* Linux only, for now.  See pq_check_connection(). */
-   if (*newval != 0)
+   if (!WaitEventSetCanReportClosed() && *newval != 0)
    {
-       GUC_check_errdetail("client_connection_check_interval must be set to 0 on platforms that lack POLLRDHUP.");
+       GUC_check_errdetail("client_connection_check_interval must be set to 0 on this platform");
        return false;
    }
-#endif
    return true;
 }
 

diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index f0786e08b48ce56dce106b456b2462bde55e2dda..d348a55812e818b2175fa1af25f8a69f9e55957d 100644 (file)
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -62,6 +62,7 @@ extern WaitEventSet *FeBeWaitSet;
 
 #define FeBeWaitSetSocketPos 0
 #define FeBeWaitSetLatchPos 1
+#define FeBeWaitSetNEvents 3
 
 extern int StreamServerPort(int family, const char *hostName,
                             unsigned short portNumber, const char *unixSocketDir,