isolationtester: append session name to application_name.

When writing / debugging an isolation test it sometimes is useful to see which
session holds what lock etc. To make it easier, both as part of spec files and
interactively, append the session name to application_name. Since b1907d6
application_name already contains the test name, this appends the session's
name to that.

insert-conflict-specconflict did something like this manually, which can now
be removed.

As we have done lately with other test infrastructure improvements, backpatch
this change, to make it easier to backpatch tests.

Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Michael Paquier <michael@paquier.xyz>
Reviewed-By: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/20211211012052.2blmzcmxnxqawd2z@alap3.anarazel.de
Backpatch: 10-, to make backpatching of tests easier.

src/test/isolation/expected/insert-conflict-specconflict.out

@@ -490,15 +490,15 @@ step controller_print_speculative_locks:
     WHERE
         locktype IN ('spectoken', 'transactionid')
         AND pa.datname = current_database()
-        AND pa.application_name LIKE 'isolation/insert-conflict-specconflict-s%'
+        AND pa.application_name LIKE 'isolation/insert-conflict-specconflict/s%'
     ORDER BY 1, 2, 3, 4;
 
 application_name                         |locktype     |mode         |granted
 -----------------------------------------+-------------+-------------+-------
-isolation/insert-conflict-specconflict-s1|spectoken    |ShareLock    |f      
-isolation/insert-conflict-specconflict-s1|transactionid|ExclusiveLock|t      
-isolation/insert-conflict-specconflict-s2|spectoken    |ExclusiveLock|t      
-isolation/insert-conflict-specconflict-s2|transactionid|ExclusiveLock|t      
+isolation/insert-conflict-specconflict/s1|spectoken    |ShareLock    |f      
+isolation/insert-conflict-specconflict/s1|transactionid|ExclusiveLock|t      
+isolation/insert-conflict-specconflict/s2|spectoken    |ExclusiveLock|t      
+isolation/insert-conflict-specconflict/s2|transactionid|ExclusiveLock|t      
 (4 rows)
 
 step controller_unlock_2_4: SELECT pg_advisory_unlock(2, 4);
@@ -517,14 +517,14 @@ step controller_print_speculative_locks:
     WHERE
         locktype IN ('spectoken', 'transactionid')
         AND pa.datname = current_database()
-        AND pa.application_name LIKE 'isolation/insert-conflict-specconflict-s%'
+        AND pa.application_name LIKE 'isolation/insert-conflict-specconflict/s%'
     ORDER BY 1, 2, 3, 4;
 
 application_name                         |locktype     |mode         |granted
 -----------------------------------------+-------------+-------------+-------
-isolation/insert-conflict-specconflict-s1|transactionid|ExclusiveLock|t      
-isolation/insert-conflict-specconflict-s1|transactionid|ShareLock    |f      
-isolation/insert-conflict-specconflict-s2|transactionid|ExclusiveLock|t      
+isolation/insert-conflict-specconflict/s1|transactionid|ExclusiveLock|t      
+isolation/insert-conflict-specconflict/s1|transactionid|ShareLock    |f      
+isolation/insert-conflict-specconflict/s2|transactionid|ExclusiveLock|t      
 (3 rows)
 
 step s2_commit: COMMIT;
@@ -544,7 +544,7 @@ step controller_print_speculative_locks:
     WHERE
         locktype IN ('spectoken', 'transactionid')
         AND pa.datname = current_database()
-        AND pa.application_name LIKE 'isolation/insert-conflict-specconflict-s%'
+        AND pa.application_name LIKE 'isolation/insert-conflict-specconflict/s%'
     ORDER BY 1, 2, 3, 4;
 
 application_name|locktype|mode|granted

src/test/isolation/isolationtester.c

@@ -154,10 +154,14 @@ main(int argc, char **argv)
 
 	for (i = 0; i < nconns; i++)
 	{
+		const char *sessionname;
+
 		if (i == 0)
-			conns[i].sessionname = "control connection";
+			sessionname = "control connection";
 		else
-			conns[i].sessionname = testspec->sessions[i - 1]->name;
+			sessionname = testspec->sessions[i - 1]->name;
+
+		conns[i].sessionname = sessionname;
 
 		conns[i].conn = PQconnectdb(conninfo);
 		if (PQstatus(conns[i].conn) != CONNECTION_OK)
@@ -182,6 +186,26 @@ main(int argc, char **argv)
 								 blackholeNoticeProcessor,
 								 NULL);
 
+		/*
+		 * Similarly, append the session name to application_name to make it
+		 * easier to map spec file sessions to log output and
+		 * pg_stat_activity. The reason to append instead of just setting the
+		 * name is that we don't know the name of the test currently running.
+		 */
+		res = PQexecParams(conns[i].conn,
+						   "SELECT set_config('application_name',\n"
+						   "  current_setting('application_name') || '/' || $1,\n"
+						   "  false)",
+						   1, NULL,
+						   &sessionname,
+						   NULL, NULL, 0);
+		if (PQresultStatus(res) != PGRES_TUPLES_OK)
+		{
+			fprintf(stderr, "setting of application name failed: %s",
+					PQerrorMessage(conns[i].conn));
+			exit(1);
+		}
+
 		/* Save each connection's backend PID for subsequent use. */
 		conns[i].backend_pid = PQbackendPID(conns[i].conn);
 		conns[i].backend_pid_str = psprintf("%d", conns[i].backend_pid);

src/test/isolation/specs/insert-conflict-specconflict.spec

@@ -47,7 +47,6 @@ session controller
 setup
 {
     SET default_transaction_isolation = 'read committed';
-    SET application_name = 'isolation/insert-conflict-specconflict-controller';
 }
 step controller_locks {SELECT pg_advisory_lock(sess, lock), sess, lock FROM generate_series(1, 2) a(sess), generate_series(1,3) b(lock);}
 step controller_unlock_1_1 { SELECT pg_advisory_unlock(1, 1); }
@@ -66,7 +65,7 @@ step controller_print_speculative_locks {
     WHERE
         locktype IN ('spectoken', 'transactionid')
         AND pa.datname = current_database()
-        AND pa.application_name LIKE 'isolation/insert-conflict-specconflict-s%'
+        AND pa.application_name LIKE 'isolation/insert-conflict-specconflict/s%'
     ORDER BY 1, 2, 3, 4;
 }
 
@@ -75,7 +74,6 @@ setup
 {
     SET default_transaction_isolation = 'read committed';
     SET spec.session = 1;
-    SET application_name = 'isolation/insert-conflict-specconflict-s1';
 }
 step s1_begin  { BEGIN; }
 step s1_create_non_unique_index { CREATE INDEX upserttest_key_idx ON upserttest((blurt_and_lock_4(key))); }
@@ -90,7 +88,6 @@ setup
 {
     SET default_transaction_isolation = 'read committed';
     SET spec.session = 2;
-    SET application_name = 'isolation/insert-conflict-specconflict-s2';
 }
 step s2_begin  { BEGIN; }
 step s2_upsert { INSERT INTO upserttest(key, data) VALUES('k1', 'inserted s2') ON CONFLICT (blurt_and_lock_123(key)) DO UPDATE SET data = upserttest.data || ' with conflict update s2'; }