Documentation on PostgreSQL service reload not interrupting open transactions?

Question

I have a version 9.5 PostgreSQL database in production that has constant traffic. I need to change a value in the pg_hba.conf file. I have confirmed on a test server that this can be put into effect by reloading the postgresql service.

I have read on other posts and sites that calling pg_ctl reload does not cause interuptions of live connections in postgresql. e.g https://dba.stackexchange.com/questions/41517/is-it-safe-to-call-pg-ctl-reload-while-doing-heavy-writes

But I am trying to find concrete documentation that calling pg_ctl reload or service postgresql-9.5 reload does not interrupt or effect any open transactions or ongoing queries to the db.

Answer 1

Here it is right from the horses mouth

reload mode simply sends the postgres process a SIGHUP signal, causing it to reread its configuration files (postgresql.conf, pg_hba.conf, etc.). This allows changing of configuration-file options that do not require a complete restart to take effect.

This signal is used by lots of other servers including Apache, NGINX etc to reread the configuration files without dropping open connections.

if you are unconvinced, try this after opening the psql client or pgadmin or whaterver

START TRANSACTION;
/* open the console and do /etc/init.d/postgrsql reload or equivalent for your system */
INSERT INTO my_table(id,name) value(1,'1');
COMMIT;

If the client has been disconnected you will be notified.