Is there a timeout for idle PostgreSQL connections?

Question

1 S postgres  5038   876  0  80   0 - 11962 sk_wai 09:57 ?        00:00:00 postgres: postgres my_app ::1(45035) idle                                                                                 
1 S postgres  9796   876  0  80   0 - 11964 sk_wai 11:01 ?        00:00:00 postgres: postgres my_app ::1(43084) idle             

I see a lot of them. We are trying to fix our connection leak. But meanwhile, we want to set a timeout for these idle connections, maybe max to 5 minute.

Answer 1

It sounds like you have a connection leak in your application because it fails to close pooled connections. You aren't having issues just with <idle> in transaction sessions, but with too many connections overall.

Killing connections is not the right answer for that, but it's an OK-ish temporary workaround.

Rather than re-starting PostgreSQL to boot all other connections off a PostgreSQL database, see: How do I detach all other users from a postgres database? and How to drop a PostgreSQL database if there are active connections to it? . The latter shows a better query.

For setting timeouts, as @Doon suggested see How to close idle connections in PostgreSQL automatically?, which advises you to use PgBouncer to proxy for PostgreSQL and manage idle connections. This is a very good idea if you have a buggy application that leaks connections anyway; I very strongly recommend configuring PgBouncer.

A TCP keepalive won't do the job here, because the app is still connected and alive, it just shouldn't be.

In PostgreSQL 9.2 and above, you can use the new state_change timestamp column and the state field of pg_stat_activity to implement an idle connection reaper. Have a cron job run something like this:

SELECT pg_terminate_backend(pid)
    FROM pg_stat_activity
    WHERE datname = 'regress'
      AND pid <> pg_backend_pid()
      AND state = 'idle'
      AND state_change < current_timestamp - INTERVAL '5' MINUTE;

In older versions you need to implement complicated schemes that keep track of when the connection went idle. Do not bother; just use pgbouncer.