[1.7] Add getSocketResource method to enhance socket management

[divinity76]

This method is a prerequisite for eventually resolving chrome-php/chrome#606

Here is my investigation notes leading up to this PR:
class \HeadlessChromium\Communication\Connection has a protected \HeadlessChromium\Communication\Socket\SocketInterface $wsClient;

\HeadlessChromium\Communication\Socket\SocketInterface has no getSocketResource().

\HeadlessChromium\Communication\Socket\Wrench must then create its own getSocketResource(),
returning the resource from protected \Wrench\Client $client;
\Wrench\Client needs a getSocketResource(), returning it's socket resource from protected \Wrench\Socket\ClientSocket $socket;

\Wrench\Socket\ClientSocket inherits $this->socket property from UriSocket...

\Wrench\Socket\UriSocket inherits $this->socket property from \Wrench\Socket\AbstractSocket...

\Wrench\Socket\AbstractSocket has a public function getResource()

that means UriSocket has it too... that means ClientSocket also has it.. \Wrench\Client needs to expose it publicly (or at least protectedly)
it needs a
public function getSocketResource(){return $this->socket->getResource();}

[GrahamCampbell]

Exposing this underlying resource feels kinda wrong. What did you need to do with the resource? I wonder if it'd be better to expose a couple of methods here to deal with that, rather than leaking the internals.

[divinity76]

@GrahamCampbell it's a long story, and the TL;DR is that in https://github.com/chrome-php/chrome/blob/1.11/src/Communication/Connection.php I want to replace

    /**
     * Wait before sending next message.
     */
    private function waitForDelay(): void
    {
        if ($this->lastMessageSentTime) {
            $currentTime = (int) (\hrtime(true) / 1000 / 1000);
            // if not enough time was spent until last message was sent, wait
            if ($this->lastMessageSentTime + $this->delay > $currentTime) {
                $timeToWait = ($this->lastMessageSentTime + $this->delay) - $currentTime;
                \usleep($timeToWait * 1000);
            }
        }

        $this->lastMessageSentTime = (int) (\hrtime(true) / 1000 / 1000);
    }

with

    /**
     * Wait before sending next message.
     */
    private function waitForDelay(): void
    {
        if ($this->lastMessageSentTime) {
            $currentTime = (int) (\hrtime(true) / 1000 / 1000);
            // if not enough time was spent until last message was sent, wait
            if ($this->lastMessageSentTime + $this->delay > $currentTime) {
                $timeToWait = ($this->lastMessageSentTime + $this->delay) - $currentTime;
                $seconds = (int)floor($timeToWait);
                $nanoseconds = (int)(($timeToWait - $seconds) * 1e9);
                $null = null;
                $read = [$this->wsClient->getSocketResource()];
                socket_select($read, $null, $null, $seconds, $nanoseconds);
            }
        }
        $this->lastMessageSentTime = (int) (\hrtime(true) / 1000 / 1000);
    }

• or something to that effect. Could make a select() method instead of a getSocketResource() method instead.

That's the short version anyway... The full version is: I wanted to make video recordings with chrome-php/chrome, and at first I tried just spamming screenshot(), and while that kindof works, it is way too slow and resource-intensive to make smooth video recordings of animations. Then I tried using Page.startScreencast + method:Page.screencastFrame instead, and that was a huge improvement over spamming screenshot() ! While much better than screenshot() spam, it still didn't produce 100% smooth recordings of animations.

I started investigating why, and I tried replacing stuff like

$navigate->waitForNavigation(\HeadlessChromium\Page::NETWORK_IDLE);

with

$target_time = microtime(true) + 5;
while (microtime(true) < $target_time) {
    // calling readData() fast causes smooth video recordings.
    // if there is too much delay in sending Page.screencastFrameAck, chromium will drop frames.
    $page->getSession()->getConnection()->readData();
}

and Yeah! Now i could make completely smooth video recordings! but it was a huge waste of CPU to busy loop like this.

Then I started investigating why I needed that loop, and it turns out that if you don't respond to a Page.screencastFrame with a Page.screencastFrameAck fast enough, Chrome will start dropping frames until you respond. That causes un-smooth choppy video recordings.

I investigated why waitForNavigation was too slow, and eventually concluded that the culprit is the usleep() in waitForDelay(), and concluded that the correct fix is to replace the usleep() with a socket_select(), and thus this PR.

[divinity76]

Perhaps we can make a PHP-alternative to NodeJS' timecut :)

[GrahamCampbell]

I wonder if it would be better to add a waitOnData() method instead of getSocketResource().

    public function waitOnData(float $maxSeconds): void
    {
        $seconds = (int)floor($timeToWait);
        $nanoseconds = (int)(($timeToWait - $seconds) * 1e9);
        $null = null;
        socket_select($this->socket, $null, $null, $seconds, $nanoseconds);
    }

    private function waitForDelay(): void
    {
        if ($this->lastMessageSentTime) {
            $currentTime = \hrtime(true) / 1000 / 1000;
            $timeToWait = (float) ($this->lastMessageSentTime + $this->delay) - $currentTime;
            // if not enough time was spent until last message was sent, wait
            if ($timeToWait > PHP_FLOAT_EPSILON)
                $this->wsClient->waitForData($timeToWait);
            }
        }
        $this->lastMessageSentTime = (int) (\hrtime(true) / 1000 / 1000);
    }

That way we're not breaking the abstraction and calling socket_select over here.

[divinity76]

I wonder if it would be better to add a waitOnData() method

sounds good! Where would it be appropriate to be defined tho? \Wrench\Client or \Wrench\Socket\ClientSocket or \Wrench\Socket\UriSocket or \Wrench\Socket\AbstractSocket ? 🤔

Edit: Just realized a mistake in my example code above, select() takes $seconds + $MICROseconds , not $NANOseconds, so the correct code is

    $seconds = (int)floor($timeToWait);
    $microseconds = (int)(($timeToWait - $seconds) * 1e6);
(...)
    socket_select($read, $null, $null, $seconds, $microseconds);

[divinity76]

@GrahamCampbell added a public function waitForData(float $maxSeconds): bool in \Wrench\Client, please re-review.

[GrahamCampbell]

Thanks.

[divinity76]

@GrahamCampbell Any ETA for a 1.7 release? kinda itching to make progress on chrome-php/chrome#606

[GrahamCampbell]

You can make progress by using ^1.7@dev for now. ;)