[Messenger] Change the default notify timeout value for PostgreSQL

[fabpot]

Q	A
Branch?	5.1
Bug fix?	yes-ish
New feature?	no
Deprecations?	no
Tickets	n/a
License	MIT
Doc PR	n/a

The default value of 0 means that notify is kind of disable and that incurs many SQL requests. 10 minutes is kind of arbitrary but seems to be a good balance between waiting for a message (blocking) and trying again later in case of an issue.

[fabpot]

@dunglas Does that make sense for you?

[dunglas]

It shouldn't be the case because of

symfony/src/Symfony/Component/Messenger/Bridge/Doctrine/Transport/PostgreSqlConnection.php

Lines 76 to 79 in b841eab

	(microtime(true) * 1000 - $this->queueEmptiedAt < $this->configuration['check_delayed_interval'])
	) {
	return null;
	}

The loop should consume some CPU to allow checking for delayed updates, but shouldn't sent useless SQL queries except when check_delayed_interval is reached.

Maybe that the default value of check_delayed_interval should be increased. But we have to find a tradeoff to support both features (delayed messages and notify). Maybe should we also make it bold in the docs that check_delayed_interval should be disabled if this feature isn't used.

By the way, we should maybe call usleep() here

symfony/src/Symfony/Component/Messenger/Bridge/Doctrine/Transport/PostgreSqlConnection.php

Line 78 in b841eab

return null;

to save some CPU.