jonathanstowe/pg-notify

Reactive interface to PostgreSQL notifies

PG::Notify

Raku interface to PostgresQL notifies.

Synopsis

use Pg::Notify;
use DBIish;

my $db = DBIish.connect('Pg', database => "dbdishtest");
my $channel = "test";

my $notify = Pg::Notify.new(:$db, :$channel );

react {
    whenever $notify -> $notification {
        say $notification.extra;
    }
	# Provide a notification
	whenever Supply.interval(1) -> $v {
		$db.do("NOTIFY $channel, '$v'");
	}
}

Description

This provides a simple mechanism to get a supply of the PostgresQL notifications for a particular channel. The supply will emit a stream of pg-notify objects corresponding to a NOTIFY executed on the connected Postgres database.

Typically the NOTIFY will be invoked in a trigger or other server side code but could just as easily be in some other user code (as in the Synopsis above,)

The objects of type Pg::Notify have a Supply method that allows coercion in places that expect a Supply (such as whenever in the Synopsis above.) but you can this Supply directly if you want to tap it for instance.

Install

This relies on DBIish and ideally you will have a working PostgreSQL database connection for the user that you will run the tests as.

For the tests you can control how it connects to the database with the environment variables:

• $PG_NOTIFY_DB - the name of the database you want to use, otherwise dbdishtest
• $PG_NOTIFY_USER - the username to be used, (otherwise will connect as the current user,)
• $PG_NOTIFY_PW - the password to be used, (otherwise no password will be used.)
• $PG_NOTIFY_HOST - the host to which the DB connection will made, the default is to connect to a local PG server.

These should be set before the tests (or install,) are run.

Assuming you have a working Rakudo installation you should just be able to use zef :

zef install Pg::Notify

# or from a local copy

zef install .

But I can't think there should be any problem with any installer that may come along in the future.

Support

This relies on the poll C library function, on Linux this is part of the runtime library that is always loaded but it might not be on other operating systems, if you have one of those systems I'd be grateful for a patch to make it work there.

If you have any other suggestions or problems please report at https://github.com/jonathanstowe/Pg-Notify/issues

Copyright and Licence

This is free software, please see the LICENCE file in the distribution.

© Jonathan Stowe 2017 - 2021