BUG #15979: PG_VERSION , pg_tblspc got deleted automatically & postgres server creased.

The following bug has been logged on the website:

Bug reference: 15979
Logged by: mahesh Shetty
Email address: maheshetty20(at)gmail(dot)com
PostgreSQL version: 9.4.4
Operating system: Oracle Linux Server release 6.7
Description:

Investigation through postmaster while starting the database service to get
DB connect:

-bash-4.1$ /usr/pgsql-9.4/bin/postgres -D /var/lib/pgsql/9.4/data <
2019-08-20 00:13:29.353 CDT >FATAL: "/var/lib/pgsql/9.4/data" is not a
valid data directory < 2019-08-20 00:13:29.353 CDT >DETAIL: File
"/var/lib/pgsql/9.4/data/PG_VERSION" is missing.
There was missing PG_VERSION which was created manually

-bash-4.1$ postmaster -D /var/lib/pgsql/9.4/data/ < 2019-08-20 00:27:35.275
CDT >FATAL: could not open directory "pg_tblspc": No such file or directory
-bash-4.1$
There was missing pg_tblspc which was created manually

-bash-4.1$ /usr/pgsql-9.4/bin/pg_ctl -D /var/lib/pgsql/9.4/data/ start
server starting
-bash-4.1$ < 2019-08-20 00:29:31.982 CDT >LOG: redirecting log output to
logging collector process < 2019-08-20 00:29:31.982 CDT >HINT: Future log
output will appear in directory "pg_log".
-bash-4.1$ psql -p 1433
psql: FATAL: the database system is starting up
-bash-4.1$ postmaster -D /var/lib/pgsql/9.4/data/ < 2019-08-20 00:29:47.588
CDT >FATAL: lock file "postmaster.pid" already exists < 2019-08-20
00:29:47.588 CDT >HINT: Is another postmaster (PID 30083) running in data
directory "/var/lib/pgsql/9.4/data"? -bash-4.1$ psql -p 1433 psql: FATAL:
the database system is starting up

Deleted manually pid files and started postgres service
-bash-4.1$ /usr/pgsql-9.4/bin/pg_ctl -D /var/lib/pgsql/9.4/data/ start
pg_ctl: another server might be running; trying to start server anyway
server starting -bash-4.1$ < 2019-08-20 00:31:04.932 CDT >FATAL: lock file
"postmaster.pid" already exists < 2019-08-20 00:31:04.932 CDT >HINT: Is
another postmaster (PID 30083) running in data directory
"/var/lib/pgsql/9.4/data"?
-bash-4.1$ psql -p 1433 psql: FATAL: the database system is starting up
-bash-4.1$



Server went into recovery mode as it was stopped abruptly.
• postgres 30083 1 0 00:29 pts/1 00:00:00
/usr/pgsql-9.4/bin/postgres -D /var/lib/pgsql/9.4/data
postgres 30084 30083 0 00:29 ? 00:00:00 postgres: logger process
postgres 30085 30083 86 00:29 ? 00:01:48 postgres: startup process
recovering 0000000100000EA9000000A6

• postgres=# SELECT * FROM pg_stat_activity;
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Succeeded.

• Connections got normal after successful recovery:
214847 | jiradb_7_0_10 | 31453 | 16385 | jirauser | |
172.28.50.226 | | 57530 | 2019-08-20
00:33:54.444258-05 |
| 2019-08-20 00:36:57.03654-05 | 2019-08-20
00:36:57.276092-05 | f | idle | |
| SELECT COUNT(I.ID) FROM
public.jiraissue I WHERE I.PROJECT=$1
214847 | jiradb_7_0_10 | 31667 | 16385 | jirauser | |
172.28.50.226 | | 57632 | 2019-08-20
00:35:42.319525-05 | 2019-08-20 00
:36:58.355277-05 | 2019-08-20 00:36:58.355307-05 | 2019-08-20
00:36:58.355308-05 | f | active | |
1672613460 | INSERT INTO "artstatemap
" (issueid, stateid, year, month, day) SELECT issueid, stateid, $1, $2, $3
FROM "artstatemap" WHERE year=$4 AND month=$5 AND (day = $6) AND (issueid >=
$7 AND issueid <
= $8)
214847 | jiradb_7_0_10 | 31549 | 16385 | jirauser | |
172.28.50.226 | | 57576 | 2019-08-20
00:34:44.761641-05 |
| 2019-08-20 00:36:57.363577-05 | 2019-08-20
00:36:57.363587-05 | f | idle | |
| COMMIT
13003 | postgres | 31672 | 10 | postgres | psql |
| | -1 | 2019-08-20 00:35:43.673998-05
|
| 2019-08-20 00:35:48.573473-05 | 2019-08-20
00:35:48.720062-05 | f | idle | |
| SELECT d.datname as "Nam
e",