FW: query pg_stat_ssl hang 100%cpu

Looks like an abnormal case.

From: James Pang (chaolpan)
Sent: Wednesday, September 6, 2023 9:41 AM
To: pgsql-performance(at)lists(dot)postgresql(dot)org
Subject: query pg_stat_ssl hang 100%cpu

Hi,
PGv14.8, OS RHEL8, no SSL enabled in this database, we have a lot of client sessions who check it's ssl state by query, all other sessions got done very quickly, but only 1 session hang there in 100% cpu tens of hours, even pg_terminate_backend does not make it stopped either. It looks like abnormal.

select ssl from pg_stat_ssl where pid=pg_backend_pid();

testdb=# select pid,usename,application_name,query_start,xact_start,state_change,wait_event_type,state,query from pg_stat_activity where pid=1245344;
pid | usename | application_name | query_start | xact_start | state_change | wait_event_type |
state | query
---------+---------+------------------------+------------------------------+-------------------------------+------------------------------+-----------------+
--------+--------------------------------------------------------
1245344 | test | PostgreSQL JDBC Driver | 2023-09-03 02:36:23.40238+00 | 2023-09-03 02:36:23.402331+00 | 2023-09-03 02:36:23.40238+00 | |
active | select ssl from pg_stat_ssl where pid=pg_backend_pid()
(1 row)

testdb=# select pid,usename,application_name,query_start,xact_start,state_change,wait_event_type,state,query from pg_stat_activity where pid=1245344;
pid | usename | application_name | query_start | xact_start | state_change | wait_event_type |
state | query
---------+---------+------------------------+------------------------------+-------------------------------+------------------------------+-----------------+
--------+--------------------------------------------------------
1245344 | test | PostgreSQL JDBC Driver | 2023-09-03 02:36:23.40238+00 | 2023-09-03 02:36:23.402331+00 | 2023-09-03 02:36:23.40238+00 | |
active | select ssl from pg_stat_ssl where pid=pg_backend_pid()
(1 row)

testdb=# select pid,usename,application_name,query_start,xact_start,state_change,wait_event_type,state,query from pg_stat_activity where pid=1245344;
pid | usename | application_name | query_start | xact_start | state_change | wait_event_type |
state | query
---------+---------+------------------------+------------------------------+-------------------------------+------------------------------+-----------------+
--------+--------------------------------------------------------
1245344 | test | PostgreSQL JDBC Driver | 2023-09-03 02:36:23.40238+00 | 2023-09-03 02:36:23.402331+00 | 2023-09-03 02:36:23.40238+00 | |
active | select ssl from pg_stat_ssl where pid=pg_backend_pid()
(1 row)

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ nMaj nMin WCHAN COMMAND
1245344 postgres 20 0 32.5g 12468 12164 R 99.5 0.0 4219:12 0 1343 - postgres: test testdb 10.250.193.40(48282) BIND

#0 ensure_record_cache_typmod_slot_exists (typmod=0) at typcache.c:1714
#1 0x000000000091185b in assign_record_type_typmod (tupDesc=<optimized out>, tupDesc(at)entry=0x27bc738) at typcache.c:2001
#2 0x000000000091df03 in internal_get_result_type (funcid=<optimized out>, call_expr=<optimized out>, rsinfo=<optimized out>,
resultTypeId=<optimized out>, resultTupleDesc=0x7ffc9dff8cd0) at funcapi.c:393
#3 0x000000000091e263 in get_expr_result_type (expr=expr(at)entry=0x2792798, resultTypeId=resultTypeId(at)entry=0x7ffc9dff8ccc,
resultTupleDesc=resultTupleDesc(at)entry=0x7ffc9dff8cd0) at funcapi.c:230
#4 0x00000000006a2fa5 in ExecInitFunctionScan (node=node(at)entry=0x273afa8, estate=estate(at)entry=0x269e948, eflags=eflags(at)entry=16) at nodeFunctionscan.c:370
#5 0x000000000069084e in ExecInitNode (node=node(at)entry=0x273afa8, estate=estate(at)entry=0x269e948, eflags=eflags(at)entry=16) at execProcnode.c:255
#6 0x000000000068a96d in InitPlan (eflags=16, queryDesc=0x273b2d8) at execMain.c:936
#7 standard_ExecutorStart (queryDesc=0x273b2d8, eflags=16) at execMain.c:263
#8 0x00007f67c2821d5d in pgss_ExecutorStart (queryDesc=0x273b2d8, eflags=<optimized out>) at pg_stat_statements.c:965
#9 0x00000000007fc226 in PortalStart (portal=portal(at)entry=0x26848b8, params=params(at)entry=0x0, eflags=eflags(at)entry=0, snapshot=snapshot(at)entry=0x0)
at pquery.c:514
#10 0x00000000007fa27f in exec_bind_message (input_message=0x7ffc9dff90d0) at postgres.c:1995
#11 PostgresMain (argc=argc(at)entry=1, argv=argv(at)entry=0x7ffc9dff9370, dbname=<optimized out>, username=<optimized out>) at postgres.c:4552
#12 0x000000000077a4ea in BackendRun (port=<optimized out>, port=<optimized out>) at postmaster.c:4537
#13 BackendStartup (port=<optimized out>) at postmaster.c:4259
#14 ServerLoop () at postmaster.c:1745
#15 0x000000000077b363 in PostmasterMain (argc=argc(at)entry=5, argv=argv(at)entry=0x256abc0) at postmaster.c:1417
#16 0x00000000004fec63 in main (argc=5, argv=0x256abc0) at main.c:209

Thanks,

James