v4-0001-Detect-dropped-connections-while-running-queries.patch

From 8962b1ac40cf63c90af3e65dc15d554d764483dc Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Mon, 1 Mar 2021 18:08:23 +1300
Subject: [PATCH v4 1/2] Detect dropped connections while running queries.

Provide a new optional GUC that can be used to check whether the client
connection has gone away periodically while running very long queries.

Author: Sergey Cherkashin <s.cherkashin@postgrespro.ru>
Author: <your name here>
Discussion: https://postgr.es/m/77def86b27e41f0efcba411460e929ae%40postgrespro.ru
---
 doc/src/sgml/config.sgml                      |  20 ++++
 src/backend/libpq/pqcomm.c                    |  31 +++++
 src/backend/tcop/postgres.c                   |   5 +
 src/backend/utils/init/globals.c              |   1 +
 src/backend/utils/init/postinit.c             |  13 +++
 src/backend/utils/misc/guc.c                  |  10 ++
 src/backend/utils/misc/postgresql.conf.sample |   3 +
 src/include/libpq/libpq.h                     |   2 +
 src/include/miscadmin.h                       |   3 +-
 src/include/utils/timeout.h                   |   1 +
 src/test/modules/Makefile                     |   1 +
 src/test/modules/connection/Makefile          |  16 +++
 .../connection/t/001_close_connection.pl      | 107 ++++++++++++++++++
 13 files changed, 212 insertions(+), 1 deletion(-)
 create mode 100644 src/test/modules/connection/Makefile
 create mode 100644 src/test/modules/connection/t/001_close_connection.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 967de73596..cadf6a9e7d 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -9231,6 +9231,26 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-client-connection-check-interval" xreflabel="client_connection_check_interval">
+      <term><varname>client_connection_check_interval</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>client_connection_check_interval</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Sets a time interval, in milliseconds, between periodic
+        verification of client-server connection during query execution.
+        If the client aborts the connection, the query is terminated.
+       </para>
+       <para>
+        Default value is <literal>zero</literal> - it disables connection
+        checks, so the backend will detect client disconnection only when trying
+        to send a response to the query.
+       </para>
+      </listitem>
+     </varlistentry>
+
      </variablelist>
     </sect2>
    </sect1>
diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index 4c7b1e7bfd..9f33138105 100644
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -104,6 +104,7 @@
  */
 int			Unix_socket_permissions;
 char	   *Unix_socket_group;
+int 		client_connection_check_interval;
 
 /* Where the Unix socket files are (list of palloc'd strings) */
 static List *sock_paths = NIL;
@@ -1921,3 +1922,33 @@ pq_settcpusertimeout(int timeout, Port *port)
 
 	return STATUS_OK;
 }
+
+/* --------------------------------
+ *	pq_check_client_connection - check if client connected to socket or not
+ * --------------------------------
+ */
+void pq_check_client_connection(void)
+{
+	CheckClientConnectionPending = false;
+	if (IsUnderPostmaster &&
+		MyProcPort != NULL && !PqCommReadingMsg && !PqCommBusy)
+	{
+		char nextbyte;
+		int r;
+
+#ifdef WIN32
+		pgwin32_noblock = 1;
+#endif
+		r = recv(MyProcPort->sock, &nextbyte, 1, MSG_PEEK);
+#ifdef WIN32
+		pgwin32_noblock = 0;
+#endif
+
+		if (r == 0 || (r == -1 &&
+			errno != EAGAIN && errno != EWOULDBLOCK && errno != EINTR))
+		{
+			ClientConnectionLost = true;
+			InterruptPending = true;
+		}
+	}
+}
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 8a0332dde9..c9be532362 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3061,6 +3061,8 @@ ProcessInterrupts(void)
 					(errcode(ERRCODE_ADMIN_SHUTDOWN),
 					 errmsg("terminating connection due to administrator command")));
 	}
+	if (CheckClientConnectionPending)
+		pq_check_client_connection();
 	if (ClientConnectionLost)
 	{
 		QueryCancelPending = false; /* lost connection trumps QueryCancel */
@@ -4288,6 +4290,9 @@ PostgresMain(int argc, char *argv[],
 		 */
 		CHECK_FOR_INTERRUPTS();
 		DoingCommandRead = false;
+		if (client_connection_check_interval)
+			enable_timeout_after(SKIP_CLIENT_CHECK_TIMEOUT,
+								 client_connection_check_interval);
 
 		/*
 		 * (6) check for any other interesting events that happened while we
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index a5976ad5b1..b42a516bc4 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -30,6 +30,7 @@ ProtocolVersion FrontendProtocol;
 volatile sig_atomic_t InterruptPending = false;
 volatile sig_atomic_t QueryCancelPending = false;
 volatile sig_atomic_t ProcDiePending = false;
+volatile sig_atomic_t CheckClientConnectionPending = false;
 volatile sig_atomic_t ClientConnectionLost = false;
 volatile sig_atomic_t IdleInTransactionSessionTimeoutPending = false;
 volatile sig_atomic_t IdleSessionTimeoutPending = false;
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index e5965bc517..002b6c9fd1 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -34,6 +34,7 @@
 #include "catalog/pg_db_role_setting.h"
 #include "catalog/pg_tablespace.h"
 #include "libpq/auth.h"
+#include "libpq/libpq.h"
 #include "libpq/libpq-be.h"
 #include "mb/pg_wchar.h"
 #include "miscadmin.h"
@@ -73,6 +74,7 @@ static void StatementTimeoutHandler(void);
 static void LockTimeoutHandler(void);
 static void IdleInTransactionSessionTimeoutHandler(void);
 static void IdleSessionTimeoutHandler(void);
+static void ClientCheckTimeoutHandler(void);
 static bool ThereIsAtLeastOneRole(void);
 static void process_startup_options(Port *port, bool am_superuser);
 static void process_settings(Oid databaseid, Oid roleid);
@@ -621,6 +623,7 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
 		RegisterTimeout(IDLE_IN_TRANSACTION_SESSION_TIMEOUT,
 						IdleInTransactionSessionTimeoutHandler);
 		RegisterTimeout(IDLE_SESSION_TIMEOUT, IdleSessionTimeoutHandler);
+		RegisterTimeout(SKIP_CLIENT_CHECK_TIMEOUT, ClientCheckTimeoutHandler);
 	}
 
 	/*
@@ -1243,6 +1246,16 @@ IdleSessionTimeoutHandler(void)
 	SetLatch(MyLatch);
 }
 
+static void
+ClientCheckTimeoutHandler(void)
+{
+	CheckClientConnectionPending = true;
+	InterruptPending = true;
+	if (client_connection_check_interval > 0)
+		enable_timeout_after(SKIP_CLIENT_CHECK_TIMEOUT,
+							 client_connection_check_interval);
+}
+
 /*
  * Returns true if at least one role is defined in this database cluster.
  */
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 3fd1a5fbe2..53db7b042e 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -3446,6 +3446,16 @@ static struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"client_connection_check_interval", PGC_USERSET, CLIENT_CONN_OTHER,
+			gettext_noop("Sets the time interval for checking connection with the client."),
+			gettext_noop("A value of -1 disables this feature. Zero selects a suitable default value."),
+			GUC_UNIT_MS
+		},
+		&client_connection_check_interval,
+		0, 0, INT_MAX,
+		NULL, NULL, NULL
+	},
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index ee06528bb0..6609c1426f 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -718,6 +718,9 @@
 
 #dynamic_library_path = '$libdir'
 
+#client_connection_check_interval = 1000	# set time interval between
+											# connection checks, in ms
+											# 0 is disabled
 
 #------------------------------------------------------------------------------
 # LOCK MANAGEMENT
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index b20deeb555..55e605a82e 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -71,6 +71,7 @@ extern int	pq_getbyte(void);
 extern int	pq_peekbyte(void);
 extern int	pq_getbyte_if_available(unsigned char *c);
 extern int	pq_putmessage_v2(char msgtype, const char *s, size_t len);
+extern void pq_check_client_connection(void);
 
 /*
  * prototypes for functions in be-secure.c
@@ -109,6 +110,7 @@ extern ssize_t secure_open_gssapi(Port *port);
 extern char *SSLCipherSuites;
 extern char *SSLECDHCurve;
 extern bool SSLPreferServerCiphers;
+extern int client_connection_check_interval;
 extern int	ssl_min_protocol_version;
 extern int	ssl_max_protocol_version;
 
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 1bdc97e308..39fe759e9e 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -84,7 +84,8 @@ extern PGDLLIMPORT volatile sig_atomic_t ProcDiePending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleInTransactionSessionTimeoutPending;
 extern PGDLLIMPORT volatile sig_atomic_t IdleSessionTimeoutPending;
 extern PGDLLIMPORT volatile sig_atomic_t ProcSignalBarrierPending;
-
+extern PGDLLIMPORT volatile sig_atomic_t ConfigReloadPending;
+extern PGDLLIMPORT volatile sig_atomic_t CheckClientConnectionPending;
 extern PGDLLIMPORT volatile sig_atomic_t ClientConnectionLost;
 
 /* these are marked volatile because they are examined by signal handlers: */
diff --git a/src/include/utils/timeout.h b/src/include/utils/timeout.h
index ecb2a366a5..89d94ebe18 100644
--- a/src/include/utils/timeout.h
+++ b/src/include/utils/timeout.h
@@ -32,6 +32,7 @@ typedef enum TimeoutId
 	STANDBY_LOCK_TIMEOUT,
 	IDLE_IN_TRANSACTION_SESSION_TIMEOUT,
 	IDLE_SESSION_TIMEOUT,
+	SKIP_CLIENT_CHECK_TIMEOUT,
 	/* First user-definable timeout reason */
 	USER_TIMEOUT,
 	/* Maximum number of timeout reasons */
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 5391f461a2..ac0196f711 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -7,6 +7,7 @@ include $(top_builddir)/src/Makefile.global
 SUBDIRS = \
 		  brin \
 		  commit_ts \
+		  connection \
 		  delay_execution \
 		  dummy_index_am \
 		  dummy_seclabel \
diff --git a/src/test/modules/connection/Makefile b/src/test/modules/connection/Makefile
new file mode 100644
index 0000000000..5c44d7ad40
--- /dev/null
+++ b/src/test/modules/connection/Makefile
@@ -0,0 +1,16 @@
+# src/test/modules/connection/Makefile
+
+subdir = src/test/modules/connection
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+export with_openssl
+
+check:
+	$(prove_check)
+
+installcheck:
+	$(prove_installcheck)
+
+clean distclean maintainer-clean:
+	rm -rf tmp_check
diff --git a/src/test/modules/connection/t/001_close_connection.pl b/src/test/modules/connection/t/001_close_connection.pl
new file mode 100644
index 0000000000..7f727833ec
--- /dev/null
+++ b/src/test/modules/connection/t/001_close_connection.pl
@@ -0,0 +1,107 @@
+# Check if backend stopped after client disconnection
+use strict;
+use warnings;
+use PostgresNode;
+use TestLib;
+use Test::More;
+use File::Copy;
+
+if ($ENV{with_openssl} eq 'yes')
+{
+    plan tests => 3;
+}
+else
+{
+    plan tests => 2;
+}
+
+my $long_query = q{
+DO
+$$
+DECLARE row_data RECORD;
+BEGIN
+EXECUTE 'CREATE TABLE IF NOT EXISTS keep_alive_test AS SELECT generate_series(0,100000) AS tt';
+FOR row_data IN
+    SELECT tt
+    FROM keep_alive_test
+LOOP
+    EXECUTE 'SELECT count(*) FROM keep_alive_test';
+END LOOP;
+END$$;
+};
+my $set_guc_on = q{
+    SET client_connection_check_interval = 1000;
+};
+my $set_guc_off = q{
+    SET client_connection_check_interval = 0;
+};
+my ($pid, $timed_out);
+
+my $node = get_new_node('node');
+$node->init;
+$node->start;
+
+#########################################################
+# TEST 1: GUC client_connection_check_interval: enabled #
+#########################################################
+
+# Set GUC options, get backend pid and run a long time query
+$node->psql('postgres', "$set_guc_on SELECT pg_backend_pid(); $long_query",
+            stdout => \$pid, timeout => 2, timed_out => \$timed_out);
+
+# Give time to the backend to detect client disconnected
+sleep 3;
+# Check if backend is still alive
+my $is_alive = $node->safe_psql('postgres', "SELECT count(*) FROM pg_stat_activity where pid = $pid;");
+is($is_alive, '0', 'Test: client_connection_check_interval enable');
+$node->stop;
+
+##########################################################
+# TEST 2: GUC client_connection_check_interval: disabled #
+##########################################################
+
+$node->start;
+$node->psql('postgres', "$set_guc_off SELECT pg_backend_pid(); $long_query",
+            stdout => \$pid, timeout => 2, timed_out => \$timed_out);
+# Give time to the client to disconnect
+sleep 3;
+# Check if backend is still alive
+$is_alive = $node->safe_psql('postgres', "SELECT count(*) FROM pg_stat_activity where pid = $pid;");
+is($is_alive, '1', 'Test: client_connection_check_interval disable');
+$node->stop;
+
+##########################################################
+# TEST 3: Using client_connection_check_interval when    #
+#         client connected using SSL                     #
+##########################################################
+
+if ($ENV{with_openssl} eq 'yes')
+{
+    # The client's private key must not be world-readable, so take a copy
+    # of the key stored in the code tree and update its permissions.
+    copy("../../ssl/ssl/client.key", "../../ssl/ssl/client_tmp.key");
+    chmod 0600, "../../ssl/ssl/client_tmp.key";
+    copy("../../ssl/ssl/client-revoked.key", "../../ssl/ssl/client-revoked_tmp.key");
+    chmod 0600, "../../ssl/ssl/client-revoked_tmp.key";
+    $ENV{PGHOST} = $node->host;
+    $ENV{PGPORT} = $node->port;
+
+    open my $sslconf, '>', $node->data_dir . "/sslconfig.conf";
+    print $sslconf "ssl=on\n";
+    print $sslconf "ssl_cert_file='server-cn-only.crt'\n";
+    print $sslconf "ssl_key_file='server-password.key'\n";
+    print $sslconf "ssl_passphrase_command='echo secret1'\n";
+    close $sslconf;
+
+    $node->start;
+    $node->psql('postgres', "$set_guc_on SELECT pg_backend_pid(); $long_query",
+                stdout => \$pid, timeout => 2, timed_out => \$timed_out,
+                sslmode => 'require');
+
+    # Give time to the backend to detect client disconnected
+    sleep 3;
+    # Check if backend is still alive
+    my $is_alive = $node->safe_psql('postgres', "SELECT count(*) FROM pg_stat_activity where pid = $pid;");
+    is($is_alive, '0', 'Test: client_connection_check_interval enabled, SSL');
+    $node->stop;
+}
-- 
2.30.1