Memory leak if callbacks suspend

[azjezz]

reproduce:

1. create script.php with the following content:

<?php

declare(strict_types=1);

use Revolt\EventLoop;

require __DIR__ . '/../../vendor/autoload.php';

$write_line = static fn(string $m, ...$args) => printf($m . "\n", ...$args);

$write_line('Server is listening on http://localhost:3030');

// Error reporting suppressed since stream_socket_server() emits an E_WARNING on failure (checked below).
$server = @stream_socket_server('tcp://localhost:3030', $errno, $_, flags: STREAM_SERVER_BIND | STREAM_SERVER_LISTEN, context: stream_context_create([
    'socket' => [
        'ipv6_v6only' => true,
        'so_reuseaddr' => false,
        'so_reuseport' => false,
        'so_broadcast' => false,
        'tcp_nodelay' => false,
    ]
]));
if (!$server || $errno) {
    throw new RuntimeException('Failed to listen localhost 3030.', $errno);
}

$watcher = null;
EventLoop::unreference(EventLoop::onSignal(SIGINT, static function () use ($server, &$watcher) {
    EventLoop::cancel((string) $watcher);
    fclose($server);
}));

$watcher = EventLoop::onReadable($server, function ($watcher, $resource) {
    $stream = @stream_socket_accept($resource, timeout: 0.0);
    if (false === $stream) {
        EventLoop::cancel($watcher);

        return;
    }

    stream_set_read_buffer($stream, 0);
    stream_set_blocking($stream, false);
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onReadable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    $request = stream_get_contents($stream);
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onWritable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    fwrite($stream, "HTTP/1.1 200 OK\n");
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onWritable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    fwrite($stream, "Server: TCP Server\n");
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onWritable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    fwrite($stream, "Connection: close\n");
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onWritable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    fwrite($stream, "Content-Type: text/html; charset=utf-8\n\n");
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onWritable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    fwrite($stream, "<h3>Hello, World!</h3>");
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onWritable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    fwrite($stream, "<pre><code>" . htmlentities($request) . "</code></pre>");
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onWritable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    fwrite($stream, sprintf('memory usage: %dMiB<br />', round(memory_get_usage() / 1024 / 1024, 1)));
    $suspension = EventLoop::createSuspension();
    $watcher = EventLoop::onWritable($stream, function () use ($suspension) {
        $suspension->resume();
    });
    $suspension->suspend();
    EventLoop::cancel($watcher);
    fwrite($stream, sprintf('peak memory usage: %dMiB<br />', round(\memory_get_peak_usage() / 1024 / 1024, 1)));
    @fclose($stream);
});

EventLoop::run();

$write_line('');
$write_line('Goodbye 👋');

2. run php script.php

memory keeps going up with each request ( noticeable with a request batch of 10k )

It seems suspensions are not being destructed properly and taking space in memory?

I'm not really sure what is happening, i first noticed the leak in https://github.com/azjezz/hack-php-async-io/blob/main/src/server.php, and went on simplifying the code to isolate it, until i reached this step, where no PSL code was involved, which means the leak is happening in revolt, or I'm doing something wrong.

[kelunik]

Memory usage stays the same for me:

memory usage: 3MiB
peak memory usage: 4MiB

[azjezz]

Not for me :D ( using stream select driver )

PHP 8.1.1 (cli) (built: Jan 11 2022 14:39:53) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.1.1, Copyright (c) Zend Technologies

using: siege -c 100 -t 100S -i --no-parser -b http://localhost:3030 ( seige: https://github.com/JoeDog/siege )

[kelunik]

Good point, I was using ext-uv, but same with REVOLT_DRIVER=Revolt\\EventLoop\\Driver\\StreamSelectDriver php test.php

Lifting the server siege...
Transactions:		      251743 hits
Availability:		       99.98 %
Elapsed time:		       99.61 secs
Data transferred:	       62.66 MB
Response time:		        0.02 secs
Transaction rate:	     2527.29 trans/sec
Throughput:		        0.63 MB/sec
Concurrency:		       56.48
Successful transactions:      251743
Failed transactions:	          52
Longest transaction:	       69.14
Shortest transaction:	        0.01

[trowski]

@kelunik Are you using dev-main and @azjezz is using 0.1.1?

[azjezz]

i'm using dev-cache-suspensions ( same problem for me with dev-main, and v0.1 )

> composer show revolt/event-loop
name     : revolt/event-loop
descrip. : Rock-solid event loop for concurrent PHP applications.
keywords : async, asynchronous, concurrency, event, event-loop, non-blocking, scheduler
versions : * dev-cache-suspensions
type     : library
license  : MIT License (MIT) (OSI approved) https://spdx.org/licenses/MIT.html#licenseText
homepage :
source   : [git] https://github.com/revoltphp/event-loop.git 8f4a8e9fcbaf22106613abbf2a0bfb9dfe59f854
dist     : [zip] https://api.github.com/repos/revoltphp/event-loop/zipball/8f4a8e9fcbaf22106613abbf2a0bfb9dfe59f854 8f4a8e9fcbaf22106613abbf2a0bfb9dfe59f854
path     : /home/azjezz/Projects/php-standard-library/vendor/revolt/event-loop
names    : revolt/event-loop

support
issues : https://github.com/revoltphp/event-loop/issues
source : https://github.com/revoltphp/event-loop/tree/cache-suspensions

autoload
psr-4
Revolt\ => src

requires
php >=8.0.7

requires (dev)
ext-json *
jetbrains/phpstorm-stubs ^2019.3
phpunit/phpunit ^9
psalm/phar ^4.7

[azjezz]

Also to note, i'm using WSL2, but i really hope that's irrelevant :D

> php --version && php -m && neofetch
PHP 8.1.1 (cli) (built: Jan 11 2022 14:39:53) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.1.1, Copyright (c) Zend Technologies
[PHP Modules]
bcmath
bz2
calendar
Core
ctype
curl
date
dba
dom
exif
fileinfo
filter
ftp
gettext
gmp
hash
iconv
intl
json
ldap
libxml
mbstring
memprof
mysqli
mysqlnd
openssl
pcntl
pcre
PDO
pdo_mysql
pdo_pgsql
pdo_sqlite
pgsql
Phar
posix
readline
Reflection
session
shmop
SimpleXML
soap
sockets
sodium
SPL
sqlite3
standard
sysvmsg
sysvsem
sysvshm
tokenizer
xml
xmlreader
xmlwriter
xsl
zip
zlib

[Zend Modules]

            .-/+oossssoo+/-.               azjezz@Lua
        `:+ssssssssssssssssss+:`           ----------
      -+ssssssssssssssssssyyssss+-         OS: Ubuntu 20.04.3 LTS on Windows 10 x86_64
    .ossssssssssssssssssdMMMNysssso.       Kernel: 5.10.60.1-microsoft-standard-WSL2
   /ssssssssssshdmmNNmmyNMMMMhssssss/      Uptime: 3 hours, 8 mins
  +ssssssssshmydMMMMMMMNddddyssssssss+     Packages: 2050 (dpkg)
 /sssssssshNMMMyhhyyyyhmNMMMNhssssssss/    Shell: zsh 5.8
.ssssssssdMMMNhsssssssssshNMMMdssssssss.   Terminal: /dev/pts/2
+sssshhhyNMMNyssssssssssssyNMMMysssssss+   CPU: AMD Ryzen 7 3750H with Radeon Vega Mobile Gfx (4) @ 2.295GHz
ossyNMMMNyMMhsssssssssssssshmmmhssssssso   Memory: 117MiB / 9959MiB
ossyNMMMNyMMhsssssssssssssshmmmhssssssso
+sssshhhyNMMNyssssssssssssyNMMMysssssss+
.ssssssssdMMMNhsssssssssshNMMMdssssssss.
 /sssssssshNMMMyhhyyyyhdNMMMNhssssssss/
  +sssssssssdmydMMMMMMMMddddyssssssss+
   /ssssssssssshdmNNNNmyNMMMMhssssss/
    .ossssssssssssssssssdMMMNysssso.
      -+sssssssssssssssssyyyssss+-
        `:+ssssssssssssssssss+:`
            .-/+oossssoo+/-.

[kelunik]

@trowski Can you reproduce it?

@azjezz Maybe WSL 2 doesn't handle mmap correctly? Just a thing that comes to my mind.

[trowski]

No, I get similar results to you after thousands of requests.

memory usage: 2MiB
peak memory usage: 4MiB

[kelunik]

I can reproduce it on WSL, but also get lots of errors logged from siege:

[error] unable to set close control sock.c:141: Invalid argument
[error] unable to set close control sock.c:141: Invalid argument
[error] unable to set close control sock.c:141: Invalid argument
[error] unable to set close control sock.c:141: Invalid argument

[kelunik]

I can reproduce it on Windows with WSL 1 and directly without WSL at all.

[kelunik]

I simple script like the following does not reproduce any leak for me:

<?php

$i = 0;

while (true) {
        $fiber = new Fiber(function () {
                while (true) {
                        Fiber::suspend();
                }
        });

        $fiber->start();
        $fiber->resume();

        if (++$i % 100000 === 0) {
                print \memory_get_usage(true) . PHP_EOL;
        }
}

[sorenbronsted]

I have the same issue on Linux/Ubuntu. if you comment out readHeaders it is not leaking. Here is my example:

<?php

use Revolt\EventLoop;

require __DIR__ . '/vendor/autoload.php';


function readHttpLine($stream): string
{
    $stop = false;
    $chars = '';
    $suspension = EventLoop::getSuspension();
    $watcher = EventLoop::onReadable($stream, fn () => $suspension->resume());
    while(!feof($stream) && !$stop) {
        do {
            $byte = fread($stream, 1);
            $chars .= $byte;
        } while($byte && $byte != "\n");
        $stop = (strlen($chars) > 1 && $chars[-1] == "\n");
        if (!$stop) {
            $suspension->suspend();
        }
    }
    EventLoop::cancel($watcher);
    return $chars;
}

function readHeaders($stream)
{
    $stop = false;
    while(!$stop) {
        $line = readHttpLine($stream);
        echo trim($line) . PHP_EOL;
        // end-of-headers is one line with \r\n
        $stop = (strlen($line) == 2 && $line[0] == "\r" && $line[1] == "\n");
    }
}

function run()
{
    // start TCP/IP server on localhost:8080
    // for illustration purposes only, should use socket abstracting instead
    $server = \stream_socket_server('tcp://0.0.0.0:8000');
    if (!$server) {
        exit(1);
    }
    \stream_set_blocking($server, false);

    echo "Visit http://localhost:8080/ in your browser." . PHP_EOL;

    // wait for incoming connections on server socket
    EventLoop::onReadable($server, function ($watcher, $server) {
        $conn = \stream_socket_accept($server);
        \stream_set_blocking($conn, false);
        readHeaders($conn);
        $data = "HTTP/1.1 200 OK\r\nConnection: close\r\nContent-Length: 3\r\n\r\nHi\n";
        EventLoop::onWritable($conn, function ($watcher, $conn) use (&$data) {
            $written = \fwrite($conn, $data);
            if ($written === \strlen($data)) {
                \fclose($conn);
                EventLoop::cancel($watcher);
            } else {
                $data = \substr($data, $written);
            }
        });
    });

    EventLoop::repeat(2, function () {
        $memory = \memory_get_usage() / 1024;
        $formatted = \number_format($memory) . ' KiB';
        echo "Current memory usage: {$formatted}\n";
    });

    EventLoop::run();
}

run();