Restart the apply worker if the privileges have been revoked.

Restart the apply worker if the subscription owner's superuser privileges
have been revoked. This is required so that the subscription connection
string gets revalidated and use the password option to connect to the
publisher for non-superusers, if required.

Author: Vignesh C
Reviewed-by: Amit Kapila
Discussion: http://postgr.es/m/CALDaNm2Dxmhq08nr4P6G+24QvdBo_GAVyZ_Q1TcGYK+8NHs9xw@mail.gmail.com

src/backend/catalog/pg_subscription.c

@@ -108,6 +108,9 @@ GetSubscription(Oid subid, bool missing_ok)
 								   Anum_pg_subscription_suborigin);
 	sub->origin = TextDatumGetCString(datum);
 
+	/* Is the subscription owner a superuser? */
+	sub->ownersuperuser = superuser_arg(sub->owner);
+
 	ReleaseSysCache(tup);
 
 	return sub;

src/backend/commands/subscriptioncmds.c

@@ -869,7 +869,7 @@ AlterSubscription_refresh(Subscription *sub, bool copy_data,
 	load_file("libpqwalreceiver", false);
 
 	/* Try to connect to the publisher. */
-	must_use_password = !superuser_arg(sub->owner) && sub->passwordrequired;
+	must_use_password = sub->passwordrequired && !sub->ownersuperuser;
 	wrconn = walrcv_connect(sub->conninfo, true, must_use_password,
 							sub->name, &err);
 	if (!wrconn)
@@ -1249,7 +1249,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 			load_file("libpqwalreceiver", false);
 			/* Check the connection info string. */
 			walrcv_check_conninfo(stmt->conninfo,
-								  sub->passwordrequired && !superuser_arg(sub->owner));
+								  sub->passwordrequired && !sub->ownersuperuser);
 
 			values[Anum_pg_subscription_subconninfo - 1] =
 				CStringGetTextDatum(stmt->conninfo);

src/backend/replication/logical/tablesync.c

@@ -1275,13 +1275,11 @@ LogicalRepSyncTableStart(XLogRecPtr *origin_startpos)
 	relstate = GetSubscriptionRelState(MyLogicalRepWorker->subid,
 									   MyLogicalRepWorker->relid,
 									   &relstate_lsn);
+	CommitTransactionCommand();
 
 	/* Is the use of a password mandatory? */
 	must_use_password = MySubscription->passwordrequired &&
-		!superuser_arg(MySubscription->owner);
-
-	/* Note that the superuser_arg call can access the DB */
-	CommitTransactionCommand();
+		!MySubscription->ownersuperuser;
 
 	SpinLockAcquire(&MyLogicalRepWorker->relmutex);
 	MyLogicalRepWorker->relstate = relstate;

src/backend/replication/logical/worker.c

@@ -3966,6 +3966,24 @@ maybe_reread_subscription(void)
 		apply_worker_exit();
 	}
 
+	/*
+	 * Exit if the subscription owner's superuser privileges have been
+	 * revoked.
+	 */
+	if (!newsub->ownersuperuser && MySubscription->ownersuperuser)
+	{
+		if (am_parallel_apply_worker())
+			ereport(LOG,
+					errmsg("logical replication parallel apply worker for subscription \"%s\" will stop because the subscription owner's superuser privileges have been revoked",
+						   MySubscription->name));
+		else
+			ereport(LOG,
+					errmsg("logical replication worker for subscription \"%s\" will restart because the subscription owner's superuser privileges have been revoked",
+						   MySubscription->name));
+
+		apply_worker_exit();
+	}
+
 	/* Check for other changes that should never happen too. */
 	if (newsub->dbid != MySubscription->dbid)
 	{
@@ -4492,13 +4510,11 @@ run_apply_worker()
 	replorigin_session_setup(originid, 0);
 	replorigin_session_origin = originid;
 	origin_startpos = replorigin_session_get_progress(false);
+	CommitTransactionCommand();
 
 	/* Is the use of a password mandatory? */
 	must_use_password = MySubscription->passwordrequired &&
-		!superuser_arg(MySubscription->owner);
-
-	/* Note that the superuser_arg call can access the DB */
-	CommitTransactionCommand();
+		!MySubscription->ownersuperuser;
 
 	LogRepWorkerWalRcvConn = walrcv_connect(MySubscription->conninfo, true,
 											must_use_password,
@@ -4621,11 +4637,18 @@ InitializeLogRepWorker(void)
 	SetConfigOption("synchronous_commit", MySubscription->synccommit,
 					PGC_BACKEND, PGC_S_OVERRIDE);
 
-	/* Keep us informed about subscription changes. */
+	/*
+	 * Keep us informed about subscription or role changes. Note that the
+	 * role's superuser privilege can be revoked.
+	 */
 	CacheRegisterSyscacheCallback(SUBSCRIPTIONOID,
 								  subscription_change_cb,
 								  (Datum) 0);
 
+	CacheRegisterSyscacheCallback(AUTHOID,
+								  subscription_change_cb,
+								  (Datum) 0);
+
 	if (am_tablesync_worker())
 		ereport(LOG,
 				(errmsg("logical replication table synchronization worker for subscription \"%s\", table \"%s\" has started",

src/include/catalog/pg_subscription.h

@@ -127,6 +127,7 @@ typedef struct Subscription
 								 * skipped */
 	char	   *name;			/* Name of the subscription */
 	Oid			owner;			/* Oid of the subscription owner */
+	bool		ownersuperuser; /* Is the subscription owner a superuser? */
 	bool		enabled;		/* Indicates if the subscription is enabled */
 	bool		binary;			/* Indicates if the subscription wants data in
 								 * binary format */

src/test/subscription/t/027_nosuperuser.pl

@@ -104,6 +104,7 @@ for my $node ($node_publisher, $node_subscriber)
   CREATE ROLE regress_admin SUPERUSER LOGIN;
   CREATE ROLE regress_alice NOSUPERUSER LOGIN;
   GRANT CREATE ON DATABASE postgres TO regress_alice;
+  GRANT PG_CREATE_SUBSCRIPTION TO regress_alice;
   SET SESSION AUTHORIZATION regress_alice;
   CREATE SCHEMA alice;
   GRANT USAGE ON SCHEMA alice TO regress_admin;
@@ -303,4 +304,27 @@ GRANT SELECT ON alice.unpartitioned TO regress_alice;
 expect_replication("alice.unpartitioned", 3, 17, 21,
 	"restoring SELECT permission permits replication to continue");
 
+# The apply worker should get restarted after the superuser privileges are
+# revoked for subscription owner alice.
+grant_superuser("regress_alice");
+$node_subscriber->safe_psql(
+	'postgres', qq(
+SET SESSION AUTHORIZATION regress_alice;
+CREATE SUBSCRIPTION regression_sub CONNECTION '$publisher_connstr' PUBLICATION alice;
+));
+
+# Wait for initial sync to finish
+$node_subscriber->wait_for_subscription_sync($node_publisher,
+	'regression_sub');
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+revoke_superuser("regress_alice");
+
+# After the user becomes non-superuser the apply worker should be restarted.
+$node_subscriber->wait_for_log(
+	qr/LOG: ( [A-Z0-9]+:)? logical replication worker for subscription \"regression_sub\" will restart because the subscription owner's superuser privileges have been revoked/,
+	$offset);
+
 done_testing();