ALTER SYSTEM for tcp_keepalives_idle doesn't show up with the SHOW command.

Dear Postgres Bug list,

I read about the ALTER SYSTEM command at https://www.postgresql.org/docs/9.6/static/sql-altersystem.html and an article at
http://paquier.xyz/postgresql-2/postgres-9-4-feature-highlight-alter-system-set-for-dynamic-configuration/

and his example worked exactly as it should. However, when I tried with tcp_keepalives_idle, updates the auto.conf file as it should, but does not show up in the SHOW command... I tried it with the value 60, or '60' - didn't seem to make any difference...

postgres=# ALTER SYSTEM SET work_mem TO '10MB';
ALTER SYSTEM
postgres=# SELECT pg_reload_conf();
pg_reload_conf
----------------
t
(1 row)
postgres=# SHOW work_mem;
work_mem
----------
10MB
(1 row)

postgres=# ALTER SYSTEM SET tcp_keepalives_idle='60';
ALTER SYSTEM
postgres=# SELECT pg_reload_conf();
pg_reload_conf
----------------
t
(1 row)

postgres=# SHOW tcp_keepalives_idle;
tcp_keepalives_idle
---------------------
0
(1 row)

$ sudo cat /var/lib/postgresql/9.5/main/postgresql.auto.conf
# Do not edit this file manually!
# It will be overwritten by ALTER SYSTEM command.
tcp_keepalives_idle = '60'
work_mem = '10MB'

$ sudo -u postgres psql
psql (9.5.10)
Type "help" for help.
postgres=# SHOW work_mem;
work_mem
----------
10MB
(1 row)
postgres=# SHOW tcp_keepalives_idle;
tcp_keepalives_idle
---------------------
0
(1 row)

So, which is not working - reading from the config file, or showing the correct value?

I get the same value (0) even when I hack the main postgresql.conf file. It still shows zero. I even restarted the service - makes no difference.

-- Alan Robertson
alan(dot)robertson(at)charter(dot)com

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