Php popen / fgets time limit
I want to impose a time limit on a process read using fgets opened by popen in PHP.
I have the following code:
$handle = popen("tail -F -n 30 /tmp/pushlog.txt 2>&1", "r");
while(!feof($handle)) {
$buffer = fgets($handle);
echo "data: ".$buffer."\n";
@ob_flush();
flush();
}
pclose($handle);
I tried without success:
set_time_limit(60);
ignore_user_abort(false);
The process is as follows:
- The browser sends a GET request awaiting a response on the server side HTML5 event format.
- The request is received by the AWS load balancer and is forwarded to the EC2 instances.
- The answer is the last 30 lines of the file
- The browser receives it in 30 messages and the connection is maintained.
- If the tail command sends a newline, it returns else fgets wait undefined time until a newline is returned from the tail command.
- AWS load balancing after 60 seconds of network inactivity (no new lines in 60 seconds) closes the browser connection. The connection to the EC2 instance is not closed.
- The browser detects that the connection is closed and it opens a new connection, the process goes back to step 1.
As these steps describe, the connection between AWS Load Balancer and EC2 instance never closes, after a few hours / days, hundreds and hundreds of tail and httpd processes are running and the server is not responding.
Of course this is a bug of AWS Load Balancer, but I don't want to start the process to get attention from Amazon and wait for a fix.
My workaround is a sudo kill tail to kill the process before the server becomes unstable.
I think PHP is not stopping the script because PHP is "blocked" waiting for fgets to finish.
I know the AWS Load Balancer limit is editable, but I want to keep the default, even a higher limit will not fix the problem.
I don't know if I need to change the question of how to execute a process in linux with a time limit / timeout ?.
PHP 5.5.22 / Apache 2.4 / Linux Kernel 3.14.35-28.38.amzn1.x86_64
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Tested with PHP 5.5.20:
//Change configuration.
set_time_limit(0);
ignore_user_abort(true);
//Open pipe & set non-blocking mode.
$descriptors = array(0 => array('file', '/dev/null', 'r'),
1 => array('pipe', 'w'),
2 => array('file', '/dev/null', 'w'));
$process = proc_open('exec tail -F -n 30 /tmp/pushlog.txt 2>&1',
$descriptors, $pipes, NULL, NULL) or exit;
$stream = $pipes[1];
stream_set_blocking($stream, 0);
//Call stream_select with a 10 second timeout.
$read = array($stream); $write = NULL; $except = NULL;
while (!feof($stream) && !connection_aborted()
&& stream_select($read, $write, $except, 10)) {
//Print out all the lines we can.
while (($buffer = fgets($stream)) !== FALSE) {
echo 'data: ' . $buffer . "\n";
@ob_flush();
flush();
}
}
//Clean up.
fclose($stream);
$status = proc_get_status($process);
if ($status !== FALSE && $status['running'] === TRUE)
proc_terminate($process);
proc_close($process);
Instead of using a process file pointer, I went with my "multitasking" approach. I am using this code to spawn other "processes". A type of multitasking cheat.
I'm calling the Script, hang.php, who just hangs for 90 seconds: sleep(90)
.
You might want to adjust the stream and stream_select timeouts.
Create stream (s)
header('Content-Type: text/plain; charset=utf-8');
$timeout = 20;
$result = array();
$sockets = array();
$buffer_size = 8192;
$id = 0;
$stream = stream_socket_client("ispeedlink.com:80", $errno,$errstr, $timeout,
STREAM_CLIENT_ASYNC_CONNECT|STREAM_CLIENT_CONNECT);
if ($stream) {
$sockets[$id++] = $stream; // supports multiple sockets
$http = "GET /testbed/hang.php HTTP/1.0\r\nHost: ispeedlink.com\r\n\r\n";
fwrite($stream, $http);
}
else {
echo "$id Failed\n";
}
Additional scripts can be started by adding a stream: $sockets[$id++] = $stream;
Below will be placed something in the array $result[$id]
.
Monitoring streams:
while (count($sockets)) {
$read = $sockets;
stream_select($read, $write = NULL, $except = NULL, $timeout);
if (count($read)) {
foreach ($read as $r) {
$id = array_search($r, $sockets);
$data = fread($r, $buffer_size);
if (strlen($data) == 0) { // either reads data or EOF
echo "$id Closed: " . date('h:i:s') . "\n\n\n";
fclose($r);
unset($sockets[$id]);
}
else {
$result[$id] .= $data;
}
}
}
else {
echo 'Timeout: ' . date('h:i:s') . "\n\n\n";
break;
}
}
echo system('ps auxww');
...
When I want to kill a process I use system('ps auxww')
to get the pid and kill it withsystem("kill $pid")
kill.php
header('Content-Type: text/plain; charset=utf-8');
//system('kill 220613');
echo system('ps auxww');
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