fix: Initialize lastConnectionCheck after first connection

[artonge]

Summary

We are checking whether the DB connection is alive once every 30 seconds. But when we are lacking the last check time, we are skipping the check and reconnect logic. This is causing the reconnect logic to never fire in those cases.

Investigation

It seems to me that "those cases", are actually always the case, as upon initialization, we are not using the proper connection name to store the time.

In the connect() logic, when $this->_conn is null, $this->getConnectionName() is returning replica, so $this->lastConnectionCheck will be equal to ['replica' => time()];

server/lib/private/DB/Connection.php

Lines 215 to 221 in 60711ea

	if ($this->_conn) {
	$this->reconnectIfNeeded();
	/** @psalm-suppress InternalMethod */
	return parent::connect();
	}
	$this->lastConnectionCheck[$this->getConnectionName()] = time();

server/lib/private/DB/Connection.php

Lines 891 to 893 in 60711ea

	private function getConnectionName(): string {
	return $this->isConnectedToPrimary() ? 'primary' : 'replica';
	}

https://github.com/nextcloud/3rdparty/blob/2b6d7bf65ff242ea050e736925f752a38d8da220/doctrine/dbal/src/Connections/PrimaryReadReplicaConnection.php#L136-L139

Then, if the connection name ends up as being 'primary', the reconnect logic is skipped:

server/lib/private/DB/Connection.php

Lines 874 to 880 in 60711ea

	if (
	!isset($this->lastConnectionCheck[$this->getConnectionName()]) ||
	time() <= $this->lastConnectionCheck[$this->getConnectionName()] + 30 ||
	$this->isTransactionActive()
	) {
	return;
	}

Other solution

Find a more reliable way to get the connection name.

Follow-up of #41819

[come-nc]

• Remove the $this->lastConnectionCheck initialization code as it is useless?

Maybe move it down after the call to parent::connect? There getConnectionName should return the correct value, no?

[artonge]

Maybe move it down after the call to parent::connect? There getConnectionName should return the correct value, no?

That makes sense indeed.

[artonge]

Confirmed to improve the situation in production.