From: Peter Eisentraut <peter@eisentraut.org>
Date: Wed, 25 Jul 2018 09:18:01 +0000 (+0200)
Subject: RECONNECT command
X-Git-Tag: pgbouncer_1_9_0~6
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e24d1fa303f877238e2b6f5141cde3506e9f7b49;p=pgbouncer

RECONNECT command
---

diff --git a/doc/usage.rst b/doc/usage.rst
index aeac92d..3e62d8c 100644
--- a/doc/usage.rst
+++ b/doc/usage.rst
@@ -276,7 +276,7 @@ wait_us
 close_needed
     1 if the connection will be closed as soon as possible,
     because a configuration file reload or DNS update changed the
-    connection information.
+    connection information or **RECONNECT** was issued.
 
 ptr
     Address of internal object for this connection.
@@ -596,6 +596,33 @@ ENABLE db;
 
 Allow new client connections after a previous **DISABLE** command.
 
+RECONNECT [db];
+---------------
+
+Close each open server connection for the given database, or all
+databases, after it is released (according to the pooling mode), even
+if its lifetime is not up yet.  New server connections can be made
+immediately and will connect as necessary according to the pool size
+settings.
+
+This command is useful when the server connection setup has changed,
+for example to perform a gradual switchover to a new server.  It is
+*not* necessary to run this command when the connection string in
+pgbouncer.ini has been changed and reloaded (see **RELOAD**) or when
+DNS resolution has changed, because then the equivalent of this
+command will be run automatically.  This command is only necessary if
+something downstream of PgBouncer routes the connections.
+
+After this command is run, there could be an extended period where
+some server connections go to an old destination and some server
+connections go to a new destination.  This is likely only sensible
+when switching read-only traffic between read-only replicas, or when
+switching between nodes of a multimaster replication setup.  If all
+connections need to be switched at the same time, **PAUSE** is
+recommended instead.  To close server connections without waiting (for
+example, in emergency failover rather than gradual switchover
+scenarios), also consider **KILL**.
+
 KILL db;
 --------
 
diff --git a/src/admin.c b/src/admin.c
index e4dd684..a86fb45 100644
--- a/src/admin.c
+++ b/src/admin.c
@@ -1075,6 +1075,38 @@ static bool admin_cmd_pause(PgSocket *admin, const char *arg)
 	return true;
 }
 
+/* Command: RECONNECT */
+static bool admin_cmd_reconnect(PgSocket *admin, const char *arg)
+{
+	if (!admin->admin_user)
+		return admin_error(admin, "admin access needed");
+
+	if (!arg[0]) {
+		struct List *item;
+		PgPool *pool;
+
+		log_info("RECONNECT command issued");
+		statlist_for_each(item, &pool_list) {
+			pool = container_of(item, PgPool, head);
+			if (pool->db->admin)
+				continue;
+			tag_database_dirty(pool->db);
+		}
+	} else {
+		PgDatabase *db;
+
+		log_info("RECONNECT '%s' command issued", arg);
+		db = find_or_register_database(admin, arg);
+		if (db == NULL)
+			return admin_error(admin, "no such database: %s", arg);
+		if (db == admin->pool->db)
+			return admin_error(admin, "cannot reconnect admin db: %s", arg);
+		tag_database_dirty(db);
+	}
+
+	return admin_ready(admin, "RECONNECT");
+}
+
 /* Command: DISABLE */
 static bool admin_cmd_disable(PgSocket *admin, const char *arg)
 {
@@ -1210,6 +1242,7 @@ static bool admin_show_help(PgSocket *admin, const char *arg)
 		"\tRESUME [<db>]\n"
 		"\tDISABLE <db>\n"
 		"\tENABLE <db>\n"
+		"\tRECONNECT [<db>]\n"
 		"\tKILL <db>\n"
 		"\tSUSPEND\n"
 		"\tSHUTDOWN", "");
@@ -1285,6 +1318,7 @@ static struct cmd_lookup cmd_list [] = {
 	{"enable", admin_cmd_enable},
 	{"kill", admin_cmd_kill},
 	{"pause", admin_cmd_pause},
+	{"reconnect", admin_cmd_reconnect},
 	{"reload", admin_cmd_reload},
 	{"resume", admin_cmd_resume},
 	{"select", admin_cmd_show},
diff --git a/test/test.sh b/test/test.sh
index 2ebb530..5fc6758 100755
--- a/test/test.sh
+++ b/test/test.sh
@@ -458,6 +458,16 @@ test_database_change() {
 	test "$db1" = "p1" -a "$db2" = "p0"
 }
 
+# test reconnect
+test_reconnect() {
+	bp1=`psql -X -tAq -c "select pg_backend_pid()" p1`
+	admin "reconnect p1"
+	sleep 1
+	bp2=`psql -X -tAq -c "select pg_backend_pid()" p1`
+	echo "bp1=$bp1 bp2=$bp2"
+	test "$bp1" != "$bp2"
+}
+
 # test auth_user
 test_auth_user() {
 	admin "set auth_type='md5'"
@@ -497,6 +507,7 @@ test_suspend_resume
 test_enable_disable
 test_database_restart
 test_database_change
+test_reconnect
 "
 
 if [ $# -gt 0 ]; then