Improve test coverage for LISTEN/NOTIFY.

Back-patch commit b10f40bf0 into older branches.  This adds reporting
of NOTIFY messages to isolationtester.c, and extends the async-notify
test to include direct tests of basic NOTIFY functionality.

This provides useful infrastructure for testing a bug fix I'm about
to back-patch, and there seems no good reason not to have better tests
of LISTEN/NOTIFY in the back branches.  The commit's survived long
enough in HEAD to make it unlikely that it will cause problems.

Back-patch as far as 9.6.  isolationtester.c changed too much in 9.6
to make it sane to try to fix older branches this way, and I don't
really want to back-patch those changes too.

Discussion: https://postgr.es/m/31304.1564246011@sss.pgh.pa.us

src/test/isolation/expected/async-notify.out

@@ -1,17 +1,102 @@
 Parsed test spec with 2 sessions
 
-starting permutation: listen begin check notify check
+starting permutation: listenc notify1 notify2 notify3 notifyf
-step listen: LISTEN a;
+step listenc: LISTEN c1; LISTEN c2;
-step begin: BEGIN;
+step notify1: NOTIFY c1;
-step check: SELECT pg_notification_queue_usage() > 0 AS nonzero;
+notifier: NOTIFY "c1" with payload "" from notifier
+step notify2: NOTIFY c2, 'payload';
+notifier: NOTIFY "c2" with payload "payload" from notifier
+step notify3: NOTIFY c3, 'payload3';
+step notifyf: SELECT pg_notify('c2', NULL);
+pg_notify      
+
+               
+notifier: NOTIFY "c2" with payload "" from notifier
+
+starting permutation: listenc notifyd1 notifyd2 notifys1
+step listenc: LISTEN c1; LISTEN c2;
+step notifyd1: NOTIFY c2, 'payload'; NOTIFY c1; NOTIFY "c2", 'payload';
+notifier: NOTIFY "c2" with payload "payload" from notifier
+notifier: NOTIFY "c1" with payload "" from notifier
+step notifyd2: NOTIFY c1; NOTIFY c1; NOTIFY c1, 'p1'; NOTIFY c1, 'p2';
+notifier: NOTIFY "c1" with payload "" from notifier
+notifier: NOTIFY "c1" with payload "p1" from notifier
+notifier: NOTIFY "c1" with payload "p2" from notifier
+step notifys1: 
+	BEGIN;
+	NOTIFY c1, 'payload'; NOTIFY "c2", 'payload';
+	NOTIFY c1, 'payload'; NOTIFY "c2", 'payload';
+	SAVEPOINT s1;
+	NOTIFY c1, 'payload'; NOTIFY "c2", 'payload';
+	NOTIFY c1, 'payloads'; NOTIFY "c2", 'payloads';
+	NOTIFY c1, 'payload'; NOTIFY "c2", 'payload';
+	NOTIFY c1, 'payloads'; NOTIFY "c2", 'payloads';
+	RELEASE SAVEPOINT s1;
+	SAVEPOINT s2;
+	NOTIFY c1, 'rpayload'; NOTIFY "c2", 'rpayload';
+	NOTIFY c1, 'rpayloads'; NOTIFY "c2", 'rpayloads';
+	NOTIFY c1, 'rpayload'; NOTIFY "c2", 'rpayload';
+	NOTIFY c1, 'rpayloads'; NOTIFY "c2", 'rpayloads';
+	ROLLBACK TO SAVEPOINT s2;
+	COMMIT;
+
+notifier: NOTIFY "c1" with payload "payload" from notifier
+notifier: NOTIFY "c2" with payload "payload" from notifier
+notifier: NOTIFY "c1" with payload "payload" from notifier
+notifier: NOTIFY "c2" with payload "payload" from notifier
+notifier: NOTIFY "c1" with payload "payloads" from notifier
+notifier: NOTIFY "c2" with payload "payloads" from notifier
+
+starting permutation: llisten notify1 notify2 notify3 notifyf lcheck
+step llisten: LISTEN c1; LISTEN c2;
+step notify1: NOTIFY c1;
+step notify2: NOTIFY c2, 'payload';
+step notify3: NOTIFY c3, 'payload3';
+step notifyf: SELECT pg_notify('c2', NULL);
+pg_notify      
+
+               
+step lcheck: SELECT 1 AS x;
+x              
+
+1              
+listener: NOTIFY "c1" with payload "" from notifier
+listener: NOTIFY "c2" with payload "payload" from notifier
+listener: NOTIFY "c2" with payload "" from notifier
+
+starting permutation: listenc llisten notify1 notify2 notify3 notifyf lcheck
+step listenc: LISTEN c1; LISTEN c2;
+step llisten: LISTEN c1; LISTEN c2;
+step notify1: NOTIFY c1;
+notifier: NOTIFY "c1" with payload "" from notifier
+step notify2: NOTIFY c2, 'payload';
+notifier: NOTIFY "c2" with payload "payload" from notifier
+step notify3: NOTIFY c3, 'payload3';
+step notifyf: SELECT pg_notify('c2', NULL);
+pg_notify      
+
+               
+notifier: NOTIFY "c2" with payload "" from notifier
+step lcheck: SELECT 1 AS x;
+x              
+
+1              
+listener: NOTIFY "c1" with payload "" from notifier
+listener: NOTIFY "c2" with payload "payload" from notifier
+listener: NOTIFY "c2" with payload "" from notifier
+
+starting permutation: llisten lbegin usage bignotify usage
+step llisten: LISTEN c1; LISTEN c2;
+step lbegin: BEGIN;
+step usage: SELECT pg_notification_queue_usage() > 0 AS nonzero;
 nonzero        
 
 f              
-step notify: SELECT count(pg_notify('a', s::text)) FROM generate_series(1, 1000) s;
+step bignotify: SELECT count(pg_notify('c1', s::text)) FROM generate_series(1, 1000) s;
 count          
 
 1000           
-step check: SELECT pg_notification_queue_usage() > 0 AS nonzero;
+step usage: SELECT pg_notification_queue_usage() > 0 AS nonzero;
 nonzero        
 
 t              

src/test/isolation/isolationtester.c

@@ -23,10 +23,12 @@
 
 /*
  * conns[0] is the global setup, teardown, and watchdog connection.  Additional
- * connections represent spec-defined sessions.
+ * connections represent spec-defined sessions.  We also track the backend
+ * PID, in numeric and string formats, for each connection.
  */
 static PGconn **conns = NULL;
-static const char **backend_pids = NULL;
+static int *backend_pids = NULL;
+static const char **backend_pid_strs = NULL;
 static int	nconns = 0;
 
 /* In dry run only output permutations to be run by the tester. */
@@ -42,7 +44,7 @@ static void run_permutation(TestSpec *testspec, int nsteps, Step **steps);
 
 #define STEP_NONBLOCK	0x1		/* return 0 as soon as cmd waits for a lock */
 #define STEP_RETRY		0x2		/* this is a retry of a previously-waiting cmd */
-static bool try_complete_step(Step *step, int flags);
+static bool try_complete_step(TestSpec *testspec, Step *step, int flags);
 
 static int	step_qsort_cmp(const void *a, const void *b);
 static int	step_bsearch_cmp(const void *a, const void *b);
@@ -161,8 +163,10 @@ main(int argc, char **argv)
 	 * extra for lock wait detection and global work.
 	 */
 	nconns = 1 + testspec->nsessions;
-	conns = calloc(nconns, sizeof(PGconn *));
+	conns = (PGconn **) pg_malloc0(nconns * sizeof(PGconn *));
-	backend_pids = calloc(nconns, sizeof(*backend_pids));
+	backend_pids = pg_malloc0(nconns * sizeof(*backend_pids));
+	backend_pid_strs = pg_malloc0(nconns * sizeof(*backend_pid_strs));
+
 	for (i = 0; i < nconns; i++)
 	{
 		conns[i] = PQconnectdb(conninfo);
@@ -188,26 +192,9 @@ main(int argc, char **argv)
 								 blackholeNoticeProcessor,
 								 NULL);
 
-		/* Get the backend pid for lock wait checking. */
+		/* Save each connection's backend PID for subsequent use. */
-		res = PQexec(conns[i], "SELECT pg_backend_pid()");
+		backend_pids[i] = PQbackendPID(conns[i]);
-		if (PQresultStatus(res) == PGRES_TUPLES_OK)
+		backend_pid_strs[i] = psprintf("%d", backend_pids[i]);
-		{
-			if (PQntuples(res) == 1 && PQnfields(res) == 1)
-				backend_pids[i] = pg_strdup(PQgetvalue(res, 0, 0));
-			else
-			{
-				fprintf(stderr, "backend pid query returned %d rows and %d columns, expected 1 row and 1 column",
-						PQntuples(res), PQnfields(res));
-				exit_nicely();
-			}
-		}
-		else
-		{
-			fprintf(stderr, "backend pid query failed: %s",
-					PQerrorMessage(conns[i]));
-			exit_nicely();
-		}
-		PQclear(res);
 	}
 
 	/* Set the session index fields in steps. */
@@ -232,9 +219,9 @@ main(int argc, char **argv)
 	appendPQExpBufferStr(&wait_query,
 						 "SELECT pg_catalog.pg_isolation_test_session_is_blocked($1, '{");
 	/* The spec syntax requires at least one session; assume that here. */
-	appendPQExpBufferStr(&wait_query, backend_pids[1]);
+	appendPQExpBufferStr(&wait_query, backend_pid_strs[1]);
 	for (i = 2; i < nconns; i++)
-		appendPQExpBuffer(&wait_query, ",%s", backend_pids[i]);
+		appendPQExpBuffer(&wait_query, ",%s", backend_pid_strs[i]);
 	appendPQExpBufferStr(&wait_query, "}')");
 
 	res = PQprepare(conns[0], PREP_WAITING, wait_query.data, 0, NULL);
@@ -553,7 +540,7 @@ run_permutation(TestSpec *testspec, int nsteps, Step **steps)
 				oldstep = waiting[w];
 
 				/* Wait for previous step on this connection. */
-				try_complete_step(oldstep, STEP_RETRY);
+				try_complete_step(testspec, oldstep, STEP_RETRY);
 
 				/* Remove that step from the waiting[] array. */
 				if (w + 1 < nwaiting)
@@ -575,7 +562,8 @@ run_permutation(TestSpec *testspec, int nsteps, Step **steps)
 			nerrorstep = 0;
 			while (w < nwaiting)
 			{
-				if (try_complete_step(waiting[w], STEP_NONBLOCK | STEP_RETRY))
+				if (try_complete_step(testspec, waiting[w],
+									  STEP_NONBLOCK | STEP_RETRY))
 				{
 					/* Still blocked on a lock, leave it alone. */
 					w++;
@@ -604,14 +592,15 @@ run_permutation(TestSpec *testspec, int nsteps, Step **steps)
 		}
 
 		/* Try to complete this step without blocking.  */
-		mustwait = try_complete_step(step, STEP_NONBLOCK);
+		mustwait = try_complete_step(testspec, step, STEP_NONBLOCK);
 
 		/* Check for completion of any steps that were previously waiting. */
 		w = 0;
 		nerrorstep = 0;
 		while (w < nwaiting)
 		{
-			if (try_complete_step(waiting[w], STEP_NONBLOCK | STEP_RETRY))
+			if (try_complete_step(testspec, waiting[w],
+								  STEP_NONBLOCK | STEP_RETRY))
 				w++;
 			else
 			{
@@ -634,7 +623,7 @@ run_permutation(TestSpec *testspec, int nsteps, Step **steps)
 	/* Wait for any remaining queries. */
 	for (w = 0; w < nwaiting; ++w)
 	{
-		try_complete_step(waiting[w], STEP_RETRY);
+		try_complete_step(testspec, waiting[w], STEP_RETRY);
 		report_error_message(waiting[w]);
 	}
 
@@ -697,7 +686,7 @@ run_permutation(TestSpec *testspec, int nsteps, Step **steps)
  * a lock, returns true.  Otherwise, returns false.
  */
 static bool
-try_complete_step(Step *step, int flags)
+try_complete_step(TestSpec *testspec, Step *step, int flags)
 {
 	PGconn	   *conn = conns[1 + step->session];
 	fd_set		read_set;
@@ -706,6 +695,7 @@ try_complete_step(Step *step, int flags)
 	int			sock = PQsocket(conn);
 	int			ret;
 	PGresult   *res;
+	PGnotify   *notify;
 	bool		canceled = false;
 
 	if (sock < 0)
@@ -742,7 +732,7 @@ try_complete_step(Step *step, int flags)
 				bool		waiting;
 
 				res = PQexecPrepared(conns[0], PREP_WAITING, 1,
-									 &backend_pids[step->session + 1],
+									 &backend_pid_strs[step->session + 1],
 									 NULL, NULL, 0);
 				if (PQresultStatus(res) != PGRES_TUPLES_OK ||
 					PQntuples(res) != 1)
@@ -884,6 +874,36 @@ try_complete_step(Step *step, int flags)
 		PQclear(res);
 	}
 
+	/* Report any available NOTIFY messages, too */
+	PQconsumeInput(conn);
+	while ((notify = PQnotifies(conn)) != NULL)
+	{
+		/* Try to identify which session it came from */
+		const char *sendername = NULL;
+		char		pidstring[32];
+		int			i;
+
+		for (i = 0; i < testspec->nsessions; i++)
+		{
+			if (notify->be_pid == backend_pids[i + 1])
+			{
+				sendername = testspec->sessions[i]->name;
+				break;
+			}
+		}
+		if (sendername == NULL)
+		{
+			/* Doesn't seem to be any test session, so show the hard way */
+			snprintf(pidstring, sizeof(pidstring), "PID %d", notify->be_pid);
+			sendername = pidstring;
+		}
+		printf("%s: NOTIFY \"%s\" with payload \"%s\" from %s\n",
+			   testspec->sessions[step->session]->name,
+			   notify->relname, notify->extra, sendername);
+		PQfreemem(notify);
+		PQconsumeInput(conn);
+	}
+
 	return false;
 }
 

src/test/isolation/specs/async-notify.spec

@@ -1,14 +1,70 @@
-# Verify that pg_notification_queue_usage correctly reports a non-zero result,
+# Tests for LISTEN/NOTIFY
-# after submitting notifications while another connection is listening for
-# those notifications and waiting inside an active transaction.
 
-session "listener"
+# Most of these tests use only the "notifier" session and hence exercise only
-step "listen"	{ LISTEN a; }
+# self-notifies, which are convenient because they minimize timing concerns.
-step "begin"	{ BEGIN; }
+# Note we assume that each step is delivered to the backend as a single Query
-teardown		{ ROLLBACK; UNLISTEN *; }
+# message so it will run as one transaction.
 
 session "notifier"
-step "check"	{ SELECT pg_notification_queue_usage() > 0 AS nonzero; }
+step "listenc"	{ LISTEN c1; LISTEN c2; }
-step "notify"	{ SELECT count(pg_notify('a', s::text)) FROM generate_series(1, 1000) s; }
+step "notify1"	{ NOTIFY c1; }
+step "notify2"	{ NOTIFY c2, 'payload'; }
+step "notify3"	{ NOTIFY c3, 'payload3'; }  # not listening to c3
+step "notifyf"	{ SELECT pg_notify('c2', NULL); }
+step "notifyd1"	{ NOTIFY c2, 'payload'; NOTIFY c1; NOTIFY "c2", 'payload'; }
+step "notifyd2"	{ NOTIFY c1; NOTIFY c1; NOTIFY c1, 'p1'; NOTIFY c1, 'p2'; }
+step "notifys1"	{
+	BEGIN;
+	NOTIFY c1, 'payload'; NOTIFY "c2", 'payload';
+	NOTIFY c1, 'payload'; NOTIFY "c2", 'payload';
+	SAVEPOINT s1;
+	NOTIFY c1, 'payload'; NOTIFY "c2", 'payload';
+	NOTIFY c1, 'payloads'; NOTIFY "c2", 'payloads';
+	NOTIFY c1, 'payload'; NOTIFY "c2", 'payload';
+	NOTIFY c1, 'payloads'; NOTIFY "c2", 'payloads';
+	RELEASE SAVEPOINT s1;
+	SAVEPOINT s2;
+	NOTIFY c1, 'rpayload'; NOTIFY "c2", 'rpayload';
+	NOTIFY c1, 'rpayloads'; NOTIFY "c2", 'rpayloads';
+	NOTIFY c1, 'rpayload'; NOTIFY "c2", 'rpayload';
+	NOTIFY c1, 'rpayloads'; NOTIFY "c2", 'rpayloads';
+	ROLLBACK TO SAVEPOINT s2;
+	COMMIT;
+}
+step "usage"	{ SELECT pg_notification_queue_usage() > 0 AS nonzero; }
+step "bignotify"	{ SELECT count(pg_notify('c1', s::text)) FROM generate_series(1, 1000) s; }
+teardown		{ UNLISTEN *; }
 
-permutation "listen" "begin" "check" "notify" "check"
+# The listener session is used for cross-backend notify checks.
+
+session "listener"
+step "llisten"	{ LISTEN c1; LISTEN c2; }
+step "lcheck"	{ SELECT 1 AS x; }
+step "lbegin"	{ BEGIN; }
+teardown		{ UNLISTEN *; }
+
+
+# Trivial cases.
+permutation "listenc" "notify1" "notify2" "notify3" "notifyf"
+
+# Check simple and less-simple deduplication.
+permutation "listenc" "notifyd1" "notifyd2" "notifys1"
+
+# Cross-backend notification delivery.  We use a "select 1" to force the
+# listener session to check for notifies.  In principle we could just wait
+# for delivery, but that would require extra support in isolationtester
+# and might have portability-of-timing issues.
+permutation "llisten" "notify1" "notify2" "notify3" "notifyf" "lcheck"
+
+# Again, with local delivery too.
+permutation "listenc" "llisten" "notify1" "notify2" "notify3" "notifyf" "lcheck"
+
+# Verify that pg_notification_queue_usage correctly reports a non-zero result,
+# after submitting notifications while another connection is listening for
+# those notifications and waiting inside an active transaction.  We have to
+# fill a page of the notify SLRU to make this happen, which is a good deal
+# of traffic.  To not bloat the expected output, we intentionally don't
+# commit the listener's transaction, so that it never reports these events.
+# Hence, this should be the last test in this script.
+
+permutation "llisten" "lbegin" "usage" "bignotify" "usage"