on AfterSend event blocks sendig the view

[B0rner]

The on AfterSend event should run, after the view was send to the browser. But the browser seams to recieve the view after the AfterSend event is finish. It looks like the event behavior is lik "on BeforeSend", not "on AfterSend"

What steps will reproduce the problem?

Adding the following code block into the web.php

'components' => [
	    'response' => [
	        'class' => 'yii\web\Response',
			'on afterSend' => function ($event) {
                                sleep(10);
				Yii::debug('after send');
			},
         ]

What is the expected result?

Ever request from an browser returned immediately. The user/browser received the view, after it is rendered, without 10 seconds delay. I expect, sleep(10) is not blocking the request.

What do you get instead?

The request from the browser stops for 10 seconds. After the afterSend-sleep ist finish, the application sends the view/the brwoser receives the view. It looks like tihs event is working like an "on beforeSend" not like an "on afterSend".

Additional info

Q	A
Yii version	2.0.46
PHP version	7.4.14
Operating system	Yii2 docker container on ubuntu 20.04

[schmunk42]

What's your use-case here? Post-processing some stuff when your content is rendered?

Output flushing is heavily dependend on your setup, see also comments:

• https://www.php.net/manual/en/function.flush.php
• https://www.php.net/manual/en/function.ob-flush.php

[yii-bot]

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This is an automated comment, triggered by adding the label status:need more info.

[kamarton]

I've run into this problem before. Use case: not a response related post processing, example

• sending sentry events that have not yet been sent (slow or unstable server)
• deleting temp files created during the request
• expired file cache processing (site level)

If the request is fastcgi, then fastcgi_finish_request() is recommended.

# after send event
fastcgi_finish_request();
# request is ended by HTTP level
sleep(3600)

[samdark]

@kamarton so that's buffering that's not Yii-related, right?

[bizley]

Symfony is using that code to achieve it

public function send(): static
{
    $this->sendHeaders();
    $this->sendContent();

    if (\function_exists('fastcgi_finish_request')) {
        fastcgi_finish_request();
    } elseif (\function_exists('litespeed_finish_request')) {
        litespeed_finish_request();
    } elseif (!\in_array(\PHP_SAPI, ['cli', 'phpdbg'], true)) {
        static::closeOutputBuffers(0, true);
        flush();
    }

    return $this;
}

This is handy to proceed with some heavy processing after the response is sent to a user. Yii is not offering such solution.

[samdark]

I think we can do it as well.

[B0rner]

What's your use-case here? Post-processing some stuff when your content is rendered?

Output flushing is heavily dependend on your setup, see also comments:

• https://www.php.net/manual/en/function.flush.php
• https://www.php.net/manual/en/function.ob-flush.php

That is strange: I wrote the answer 2 days ago, but it's not in the issue timeline here.

My usecase is processing long running things, related to the request without the user needs to wait for, like calculating and writeing statistic data. In my case i have a bit longer runnig mysql-query with joins für statistic data and data-postrocessing for features.

Flushing the data using ob-flush did not solved the problem.