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I work on a somewhat large web application, and the backend is mostly in PHP. There are several places in the code where I need to complete some task, but I don't want to make the user wait for the result. For example, when creating a new account, I need to send them a welcome email. But when they hit the 'Finish Registration' button, I don't want to make them wait until the email is actually sent, I just want to start the process, and return a message to the user right away.
Up until now, in some places I've been using what feels like a hack with exec(). Basically doing things like:
exec("doTask.php $arg1 $arg2 $arg3 >/dev/null 2>&1 &");
Which appears to work, but I'm wondering if there's a better way. I'm considering writing a system which queues up tasks in a MySQL table, and a separate long-running PHP script that queries that table once a second, and executes any new tasks it finds. This would also have the advantage of letting me split the tasks among several worker machines in the future if I needed to.
Am I re-inventing the wheel? Is there a better solution than the exec() hack or the MySQL queue?
I've used the queuing approach, and it works well as you can defer that processing until your server load is idle, letting you manage your load quite effectively if you can partition off "tasks which aren't urgent" easily.
Rolling your own isn't too tricky, here's a few other options to check out:
GearMan - this answer was written in 2009, and since then GearMan looks a popular option, see comments below.
ActiveMQ if you want a full blown open source message queue.
ZeroMQ - this is a pretty cool socket library which makes it easy to write distributed code without having to worry too much about the socket programming itself. You could use it for message queuing on a single host - you would simply have your webapp push something to a queue that a continuously running console app would consume at the next suitable opportunity
beanstalkd - only found this one while writing this answer, but looks interesting
dropr is a PHP based message queue project, but hasn't been actively maintained since Sep 2010
php-enqueue is a recently (2017) maintained wrapper around a variety of queue systems
Finally, a blog post about using memcached for message queuing
Another, perhaps simpler, approach is to use ignore_user_abort - once you've sent the page to the user, you can do your final processing without fear of premature termination, though this does have the effect of appearing to prolong the page load from the user perspective.
When you just want to execute one or several HTTP requests without having to wait for the response, there is a simple PHP solution, as well.
In the calling script:
$socketcon = fsockopen($host, 80, $errno, $errstr, 10);
if($socketcon) {
$socketdata = "GET $remote_house/script.php?parameters=... HTTP 1.1\r\nHost: $host\r\nConnection: Close\r\n\r\n";
fwrite($socketcon, $socketdata);
fclose($socketcon);
}
// repeat this with different parameters as often as you like
On the called script.php, you can invoke these PHP functions in the first lines:
ignore_user_abort(true);
set_time_limit(0);
This causes the script to continue running without time limit when the HTTP connection is closed.
Another way to fork processes is via curl. You can set up your internal tasks as a webservice. For example:
http://domain/tasks/t1
http://domain/tasks/t2
Then in your user accessed scripts make calls to the service:
$service->addTask('t1', $data); // post data to URL via curl
Your service can keep track of the queue of tasks with mysql or whatever you like the point is: it's all wrapped up within the service and your script is just consuming URLs. This frees you up to move the service to another machine/server if necessary (ie easily scalable).
Adding http authorization or a custom authorization scheme (like Amazon's web services) lets you open up your tasks to be consumed by other people/services (if you want) and you could take it further and add a monitoring service on top to keep track of queue and task status.
http://domain/queue?task=t1
http://domain/queue?task=t2
http://domain/queue/t1/100931
It does take a bit of set-up work but there are a lot of benefits.
If it just a question of providing expensive tasks, in case of php-fpm is supported, why not to use fastcgi_finish_request() function?
This function flushes all response data to the client and finishes the request. This allows for time consuming tasks to be performed without leaving the connection to the client open.
You don't really use asynchronicity in this way:
Make all your main code first.
Execute fastcgi_finish_request().
Make all heavy stuff.
Once again php-fpm is needed.
I've used Beanstalkd for one project, and planned to again. I've found it to be an excellent way to run asynchronous processes.
A couple of things I've done with it are:
Image resizing - and with a lightly loaded queue passing off to a CLI-based PHP script, resizing large (2mb+) images worked just fine, but trying to resize the same images within a mod_php instance was regularly running into memory-space issues (I limited the PHP process to 32MB, and the resizing took more than that)
near-future checks - beanstalkd has delays available to it (make this job available to run only after X seconds) - so I can fire off 5 or 10 checks for an event, a little later in time
I wrote a Zend-Framework based system to decode a 'nice' url, so for example, to resize an image it would call QueueTask('/image/resize/filename/example.jpg'). The URL was first decoded to an array(module,controller,action,parameters), and then converted to JSON for injection to the queue itself.
A long running cli script then picked up the job from the queue, ran it (via Zend_Router_Simple), and if required, put information into memcached for the website PHP to pick up as required when it was done.
One wrinkle I did also put in was that the cli-script only ran for 50 loops before restarting, but if it did want to restart as planned, it would do so immediately (being run via a bash-script). If there was a problem and I did exit(0) (the default value for exit; or die();) it would first pause for a couple of seconds.
Here is a simple class I coded for my web application. It allows for forking PHP scripts and other scripts. Works on UNIX and Windows.
class BackgroundProcess {
static function open($exec, $cwd = null) {
if (!is_string($cwd)) {
$cwd = #getcwd();
}
#chdir($cwd);
if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
$WshShell = new COM("WScript.Shell");
$WshShell->CurrentDirectory = str_replace('/', '\\', $cwd);
$WshShell->Run($exec, 0, false);
} else {
exec($exec . " > /dev/null 2>&1 &");
}
}
static function fork($phpScript, $phpExec = null) {
$cwd = dirname($phpScript);
#putenv("PHP_FORCECLI=true");
if (!is_string($phpExec) || !file_exists($phpExec)) {
if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
$phpExec = str_replace('/', '\\', dirname(ini_get('extension_dir'))) . '\php.exe';
if (#file_exists($phpExec)) {
BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
}
} else {
$phpExec = exec("which php-cli");
if ($phpExec[0] != '/') {
$phpExec = exec("which php");
}
if ($phpExec[0] == '/') {
BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
}
}
} else {
if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
$phpExec = str_replace('/', '\\', $phpExec);
}
BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
}
}
}
PHP HAS multithreading, its just not enabled by default, there is an extension called pthreads which does exactly that.
You'll need php compiled with ZTS though. (Thread Safe)
Links:
Examples
Another tutorial
pthreads PECL Extension
UPDATE: since PHP 7.2 parallel extension comes into play
Tutorial/Example
reference manual
This is the same method I have been using for a couple of years now and I haven't seen or found anything better. As people have said, PHP is single threaded, so there isn't much else you can do.
I have actually added one extra level to this and that's getting and storing the process id. This allows me to redirect to another page and have the user sit on that page, using AJAX to check if the process is complete (process id no longer exists). This is useful for cases where the length of the script would cause the browser to timeout, but the user needs to wait for that script to complete before the next step. (In my case it was processing large ZIP files with CSV like files that add up to 30 000 records to the database after which the user needs to confirm some information.)
I have also used a similar process for report generation. I'm not sure I'd use "background processing" for something such as an email, unless there is a real problem with a slow SMTP. Instead I might use a table as a queue and then have a process that runs every minute to send the emails within the queue. You would need to be warry of sending emails twice or other similar problems. I would consider a similar queueing process for other tasks as well.
It's a great idea to use cURL as suggested by rojoca.
Here is an example. You can monitor text.txt while the script is running in background:
<?php
function doCurl($begin)
{
echo "Do curl<br />\n";
$url = 'http://'.$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI'];
$url = preg_replace('/\?.*/', '', $url);
$url .= '?begin='.$begin;
echo 'URL: '.$url.'<br>';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($ch);
echo 'Result: '.$result.'<br>';
curl_close($ch);
}
if (empty($_GET['begin'])) {
doCurl(1);
}
else {
while (ob_get_level())
ob_end_clean();
header('Connection: close');
ignore_user_abort();
ob_start();
echo 'Connection Closed';
$size = ob_get_length();
header("Content-Length: $size");
ob_end_flush();
flush();
$begin = $_GET['begin'];
$fp = fopen("text.txt", "w");
fprintf($fp, "begin: %d\n", $begin);
for ($i = 0; $i < 15; $i++) {
sleep(1);
fprintf($fp, "i: %d\n", $i);
}
fclose($fp);
if ($begin < 10)
doCurl($begin + 1);
}
?>
There is a PHP extension, called Swoole.
Although it might not be enabled, it is available on my hosting for being enabled at click of a button.
Worth checking it out. I haven't had time to use it yet, as I was searching here for info, when I stumbled across it and thought it worth sharing.
Unfortunately PHP does not have any kind of native threading capabilities. So I think in this case you have no choice but to use some kind of custom code to do what you want to do.
If you search around the net for PHP threading stuff, some people have come up with ways to simulate threads on PHP.
If you set the Content-Length HTTP header in your "Thank You For Registering" response, then the browser should close the connection after the specified number of bytes are received. This leaves the server side process running (assuming that ignore_user_abort is set) so it can finish working without making the end user wait.
Of course you will need to calculate the size of your response content before rendering the headers, but that's pretty easy for short responses (write output to a string, call strlen(), call header(), render string).
This approach has the advantage of not forcing you to manage a "front end" queue, and although you may need to do some work on the back end to prevent racing HTTP child processes from stepping on each other, that's something you needed to do already, anyway.
If you don't want the full blown ActiveMQ, I recommend to consider RabbitMQ. RabbitMQ is lightweight messaging that uses the AMQP standard.
I recommend to also look into php-amqplib - a popular AMQP client library to access AMQP based message brokers.
Spawning new processes on the server using exec() or directly on another server using curl doesn't scale all that well at all, if we go for exec you are basically filling your server with long running processes which can be handled by other non web facing servers, and using curl ties up another server unless you build in some sort of load balancing.
I have used Gearman in a few situations and I find it better for this sort of use case. I can use a single job queue server to basically handle queuing of all the jobs needing to be done by the server and spin up worker servers, each of which can run as many instances of the worker process as needed, and scale up the number of worker servers as needed and spin them down when not needed. It also let's me shut down the worker processes entirely when needed and queues the jobs up until the workers come back online.
i think you should try this technique it will help to call as many as pages you like all pages will run at once independently without waiting for each page response as asynchronous.
cornjobpage.php //mainpage
<?php
post_async("http://localhost/projectname/testpage.php", "Keywordname=testValue");
//post_async("http://localhost/projectname/testpage.php", "Keywordname=testValue2");
//post_async("http://localhost/projectname/otherpage.php", "Keywordname=anyValue");
//call as many as pages you like all pages will run at once independently without waiting for each page response as asynchronous.
?>
<?php
/*
* Executes a PHP page asynchronously so the current page does not have to wait for it to finish running.
*
*/
function post_async($url,$params)
{
$post_string = $params;
$parts=parse_url($url);
$fp = fsockopen($parts['host'],
isset($parts['port'])?$parts['port']:80,
$errno, $errstr, 30);
$out = "GET ".$parts['path']."?$post_string"." HTTP/1.1\r\n";//you can use POST instead of GET if you like
$out.= "Host: ".$parts['host']."\r\n";
$out.= "Content-Type: application/x-www-form-urlencoded\r\n";
$out.= "Content-Length: ".strlen($post_string)."\r\n";
$out.= "Connection: Close\r\n\r\n";
fwrite($fp, $out);
fclose($fp);
}
?>
testpage.php
<?
echo $_REQUEST["Keywordname"];//case1 Output > testValue
?>
PS:if you want to send url parameters as loop then follow this answer :https://stackoverflow.com/a/41225209/6295712
PHP is a single-threaded language, so there is no official way to start an asynchronous process with it other than using exec or popen. There is a blog post about that here. Your idea for a queue in MySQL is a good idea as well.
Your specific requirement here is for sending an email to the user. I'm curious as to why you are trying to do that asynchronously since sending an email is a pretty trivial and quick task to perform. I suppose if you are sending tons of email and your ISP is blocking you on suspicion of spamming, that might be one reason to queue, but other than that I can't think of any reason to do it this way.
I want to write an Ajax web application, a game to be specific. Two web clients have to communicate with each other via the PHP server. My approach to solve this is to use Ajax between client and server and server and client. Each client creates a separate server process using Ajax. I want that these two server processes communicate via MySQL and via named pipes. I need the named pipes to get immediate response for the whole application.
I cannot use one server process, which first creates a pipe and then forks into two processes, which use the pipe. Web applications create server processes when the web-browser sends a request. So, I need named pipes, where each process doesn't know more than the file name of the named pipe. They cannot exchange file handles (at least I don't know how).
My problem is that named pipes in the PHP way indeed work as long as they are
used within the same function:
public function writeAndReadPipe_test(){
$pipeA = fopen("testpipe",'r+');
fwrite($pipeA, 'ABCD');
$pipeB = fopen("testpipe",'r+');
$content = fread($pipeB, 4);
echo "[" . $content . "]<br>\n";
}
public function testingPipes_same_function(){
posix_mkfifo("testpipe", 0777);
$this->writeAndReadPipe_test();
}
But, when I use different functions, then the fread($pipeB, 4) command blocks the whole application:
public function writePipe_test(){
$pipeA = fopen("testpipe",'r+');
fwrite($pipeA, 'ABCD');
}
public function readPipe_test(){
$pipeB = fopen("testpipe",'r+');
$content = fread($pipeB, 4);
echo "[" . $content . "]<br>\n";
}
public function testingPipes_different_functions(){
posix_mkfifo("testpipe", 0777);
$this->writePipe_test();
$this->readPipe_test();
}
Does anybody know why? And what can I do to make it work between different functions in the first step? In the second step, it should work even between different processes! I found out that I also get a problem when the writer closes the pipe before the reader reads from
it. I suppose that the function closes it automatically when it ends, but this is only a guess.
If the PHP way does not work, I plan to let PHP open a command line, generate BASH commands and let execute them. This should work in any case as long as my web-server works in a LAMP environment. Disadvantage is that it will not work in WAMP environments.
So, has anybody some ideas to this?
P.S:
I need blocking pipes to let the reader wait until an event is sent. I know that the pipes can work in a non-blocking mode using
stream_set_blocking($pipe,false);
or so, but the whole idea is to do it without polling just using a pipe, which wakes the
reader up as soon as an event is fired.
Just a short statement, that I actually found a nice solution
using named pipes:
public function createPipe_test(){
posix_mkfifo("testpipe", 0777);
}
public function writePipe_test($value){
$pipeA = fopen("testpipe",'w');
$valueString = number_format($value);
$valueLen = number_format(strlen($valueString));
fwrite($pipeA, $valueLen);
fwrite($pipeA, $valueString);
}
public function readPipe_test(){
$pipeB = fopen("testpipe",'r');
$valueLen = fread($pipeB, 1);
return fread($pipeB, $valueLen);
}
I have two processes.
If process 1 calls writePipe_test(), then it waits until process 2 calls
readPipe_test() to read the data out of the pipe.
If process 1 calls readPipe_test(), then it waits until process 2 calls
writePipe_test() to write something into the pipe.
The trick is 'w' and 'r' instead of 'r+'.
When you use the pipes in separate functions like this, the write pipe A would seem to be closed/discarded again (local scope of $pipeA). The assumption would be that the pipe must be opened for reading and/or writing in order to retain any info, which makes sense really. Though I don't know the inner magic.
You can also observe that your blocking read-call succeeds when you feed the pipe from another process (like echo magic >> testpipe). So you'd already have step 2 done, but you need some pipehandle management.
If you change it as follows it'd work:
private $pipeA;
public function writePipe_test(){
$this->pipeA = fopen("testpipe",'r+');
fwrite($this->pipeA, 'ABCD');
}
Edit: or setting $pipeA to have global scope, for that matter..
Im not sure wether I understand your 2nd last post..
But to comment on the last one, if I don't misunderstand, TCP might be even more complex because you will have to establish a connection before you can either read or write, so youve got different overhead
As for the pipehandle closing at the function end, I assume you'll face the same problem with the sockets; but the pipefile remains!
Persistent storage (files,db) would make the clients independent timingwise, if you want to use blocking calls then files might actually be a way to go..
Can PHP call a function and don't wait for it to return? So something like this:
function callback($pause, $arg) {
sleep($pause);
echo $arg, "\n";
}
header('Content-Type: text/plain');
fast_call_user_func_array('callback', array(3, 'three'));
fast_call_user_func_array('callback', array(2, 'two'));
fast_call_user_func_array('callback', array(1, 'one'));
would output
one (after 1 second)
two (after 2 seconds)
three (after 3 seconds)
rather than
three (after 3 seconds)
two (after 3 + 2 = 5 seconds)
one (after 3 + 2 + 1 = 6 seconds)
Main script is intended to be run as a permanent process (TCP server). callback() function would receive data from client, execute external PHP script and then do something based on other arguments that are passed to callback(). The problem is that main script must not wait for external PHP script to finish. Result of external script is important, so exec('php -f file.php &') is not an option.
Edit:
Many have recommended to take a look at PCNTL, so it seems that such functionality can be achieved. PCNTL is not available in Windows, and I don't have an access to a Linux machine right now, so I can't test it, but if so many people have advised it, then it should do the trick :)
Thanks, everyone!
On Unix platforms you can enable the PCNTL functions, and use pcntl_fork to fork the process and run your jobs in child processes.
Something like:
function fast_call_user_func_array($func, $args) {
if (pcntl_fork() == 0) {
call_user_func_array($func, $args);
}
}
Once you call pcntl_fork, two processes will execute your code from the same position. The parent process will get a PID returned from pcntl_fork, while the child process will get 0. (If there's an error the parent process will return -1, which is worth checking for in production code).
You can check out PHP Process Control:
http://us.php.net/manual/en/intro.pcntl.php
Note: This is not threading, but the handling of separate processes. There is more overhead attached.
Wouldn't it solve your problem to fork, keeping the parent process free for other connections & actions? See http://www.php.net/pcntl_fork. If you need an answer back you could possibly listen to a socket in the parent, and write with the child. A simple while(true) loop with a read could possibly do, and probably you already have that basic functionality if you run a permanent TCP server. Another option would be to keep track of your childprocess-ids, keep a accessable store somewhere (file/database/memcached etc), with a pcnt_wait in the main process with a WNOHANG to check which process has exited, and retrieve the data from the store.
You can do some threading in PHP if you use the method pcntl_fork.
http://ca.php.net/manual/en/function.pcntl-fork.php
I have never use this myself, but the are some good example of how to use it on php.net.
PHP doesn't have this functionality as far as I know
You can emulate the function using a different technique, like this one:
Parallel functions in PHP
PHP does not support multi-threading, so there's no other option than taking advantage of the OS or the web server multi processing capabilities. Note that actually you can fetch both the result and output of exec:
string exec ( string $command [,
array &$output [, int &$return_var
]] )
You can, at least, prevent the parent process from hanging until the child process is done by ignoring the child signals using pcntl_signal(SIGCHLD, SIG_IGN).
So, let's say you want to fork a process and execute another PHP function that takes a while without making the parent wait for it to finish (since you want the main process to finish in a timely manner):
pcntl_signal(SIGCHLD, SIG_IGN);
$pid = pcntl_fork();
if ($pid < 0) {
exit(0);
} elseif (!$pid) {
my_slow_function();
exit(0);
}
// Parent keeps executing and finishes before the child does
If you want to execute a slow external script as the child process, pcntl_exec is handy:
$script = array('/path/to/my/script'); // E.g. /home/my_user/my_script.php
pcntl_exec('/path/to/program/executable',$script); // E.g. /usr/bin/php
Which design pattern exist to realize the execution of some PHP processes and the collection of the results in one PHP process?
Background:
I do have many large trees (> 10000 entries) in PHP and have to run recursive checks on it. I want to reduce the elapsed execution time.
If your goal is minimal time - the solution is simple to describe, but not that simple to implement.
You need to find a pattern to divide the work (You don't provide much information in the question in this regard).
Then use one master process that forks children to do the work. As a rule the total number of processes you use should be between n and 2n, where n is the number of cores the machine has.
Assuming this data will be stored in files you might consider using non-blocking IO to maximize the throughput. Not doing so will make most of your process spend time waiting for the disk. PHP has stream_select() that might help you. Note that using it is not trivial.
If you decide not to use select - increasing the number of processes might help.
In regards to pcntl functions: I've written a deamon with them (a proper one with forking, changing session id, the running user, etc...) and it's one of the most reliable piece of software I've written. Because it spawns workers for every task, even if there is a bug in one of the tasks, it does not affect the others.
From your php script, you could launch another script (using exec) to do the processing. Save status updates in a text file, which could then be read periodically by the parent thread.
Note: to avoid php waiting for the exec'd script to complete, pipe the output to a file:
exec('/path/to/file.php | output.log');
Alternatively, you can fork a script using the PCNTL functions. This uses one php script, which when forked can detect whether it is the parent or the child and operate accordingly. There are functions to send/receive signals for the purpose of communicating between parent/child, or you have the child log to a file and the parent read from that file.
From the pcntl_fork manual page:
$pid = pcntl_fork();
if ($pid == -1) {
die('could not fork');
} else if ($pid) {
// we are the parent
pcntl_wait($status); //Protect against Zombie children
} else {
// we are the child
}
This might be a good time to consider using a message queue, even if you run it all on one machine.
The question seems to be a bit confused.
I want to reduce the absolute execution time.
Do you mean elapsed time? Certainly use of the right data-structure will improve throughput, but for a given data-structure, the minmimum order of the algorithm is absolute, and nothing to do with how you implement the algorithm.
Which design pattern exist to realize....?
Design Patterns are something which code is, not a template for writing programs, and a useful tools for curriculum design. To start with a pattern and make your code fit it is in itself an anti-pattern.
Nobody can answer this question withuot knowing a lot more about your data and how its structured, however the key driver for efficiency will be the data-structure you use to implement your tree. If elapsed time is important then certainly look at parallel execution, however it may also be worth considering performing the operation in a different tool - databases are highly optimized for dealing with large sets of data, however note that the obvious method for describing a tree in a relational database is very inefficient when it comes to isolating sub-trees and walking the tree.
In response to Adam's suggesting of forking you replied:
I "heard" that pcntl isnt a good solution. Any experiences?
Where did you hear that? Certainly forking from a CGI or mod_php invoked script is a bad idea, but nothing wrong with doing it from the command line. Do have a google for long running PHP processes (be warned there is a lot of bad information out there). What code you write will vary depending on the underlying OS - which you've not stated.
I suspect that you could solve a large part of your performance issues by identifying which parts of the tree need to be checked and only checking those parts AND triggering the checks when the tree is updated, or at least marking the nodes as 'dirty'.
You might find these helpful:
http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/
http://en.wikipedia.org/wiki/Threaded_binary_tree
C.
You could use a more efficient data structure, such as a btree. I used once in Java but not in PHP. You can try this script: http://www.phpclasses.org/browse/file/708.html, it is an implementation of btree.
If it is not enough, you can use Hadoop to implement a Map/Reduce pattern, as Michael said. I would not fork PHP process, it does not seem to help for performace.
Personally, I would use PHP as client and put everything in Hadoop. This tutorial might help: http://www.lunchpauze.com/2007/10/writing-hadoop-mapreduce-program-in-php.html.
Another solution can be to use a Java implementation of Btree: http://jdbm.sourceforge.net/. JDBM is an object database using a Btree+ data astructures. Then you can search with PHP by exposing data with a web service or by accessing it directly with Quercus
Using web or CLI?
If you use web, you could intergrate that part in Quercus Then you could use the advantages of JAVA multithreading.
I don't actually know how reliable Quercus is though. I'd also suggest using a kind of message queue and refactoring the code, so it doesn't need the scope.
Maybe you could rebuild the code to a Map/Reduce pattern. You then can run the PHP code in Hadoop Then you can cluster the processing through a couple of machines.
I don't know if it's useful, but I came across another project, called Gearman. It's also used to cluster PHP processes. I guess you can combine that with a reduce script as well, if Hadoop is not the way you want to go.
pthreads
There is a rather new (since 2012) PHP extension available: pthreads. It can be installed via PECL.
Simple Implementation in PHP Code: extend from Thread Class. Add a run() method and execute the start() method.
<?php
// Example from http://www.phpgangsta.de/richtige-threads-in-php-einfach-erstellen-mit-pthreads
class AsyncOperation extends Thread
{
public function __construct($threadId)
{
$this->threadId = $threadId;
}
public function run()
{
printf("T %s: Sleeping 3sec\n", $this->threadId);
sleep(3);
printf("T %s: Hello World\n", $this->threadId);
}
}
$start = microtime(true);
for ($i = 1; $i <= 5; $i++) {
$t[$i] = new AsyncOperation($i);
$t[$i]->start();
}
echo microtime(true) - $start . "\n";
echo "end\n";
Outputs
>php pthreads.php
0.041301012039185
end
T 1: Sleeping 3sec
T 2: Sleeping 3sec
T 3: Sleeping 3sec
T 4: Sleeping 3sec
T 5: Sleeping 3sec
T 1: Hello World
T 2: Hello World
T 3: Hello World
T 4: Hello World
T 5: Hello World
Try this: PHPThreads
Code Example:
function threadproc($thread, $param) {
echo "\tI'm a PHPThread. In this example, I was given only one parameter: \"". print_r($param, true) ."\" to work with, but I can accept as many as you'd like!\n";
for ($i = 0; $i < 10; $i++) {
usleep(1000000);
echo "\tPHPThread working, very busy...\n";
}
return "I'm a return value!";
}
$thread_id = phpthread_create($thread, array(), "threadproc", null, array("123456"));
echo "I'm the main thread doing very important work!\n";
for ($n = 0; $n < 5; $n++) {
usleep(1000000);
echo "Main thread...working!\n";
}
echo "\nMain thread done working. Waiting on our PHPThread...\n";
phpthread_join($thread_id, $retval);
echo "\n\nOur PHPThread returned: " . print_r($retval, true) . "!\n";
Requires PHP extensions:
posix
pcntl
sockets
I work on a somewhat large web application, and the backend is mostly in PHP. There are several places in the code where I need to complete some task, but I don't want to make the user wait for the result. For example, when creating a new account, I need to send them a welcome email. But when they hit the 'Finish Registration' button, I don't want to make them wait until the email is actually sent, I just want to start the process, and return a message to the user right away.
Up until now, in some places I've been using what feels like a hack with exec(). Basically doing things like:
exec("doTask.php $arg1 $arg2 $arg3 >/dev/null 2>&1 &");
Which appears to work, but I'm wondering if there's a better way. I'm considering writing a system which queues up tasks in a MySQL table, and a separate long-running PHP script that queries that table once a second, and executes any new tasks it finds. This would also have the advantage of letting me split the tasks among several worker machines in the future if I needed to.
Am I re-inventing the wheel? Is there a better solution than the exec() hack or the MySQL queue?
I've used the queuing approach, and it works well as you can defer that processing until your server load is idle, letting you manage your load quite effectively if you can partition off "tasks which aren't urgent" easily.
Rolling your own isn't too tricky, here's a few other options to check out:
GearMan - this answer was written in 2009, and since then GearMan looks a popular option, see comments below.
ActiveMQ if you want a full blown open source message queue.
ZeroMQ - this is a pretty cool socket library which makes it easy to write distributed code without having to worry too much about the socket programming itself. You could use it for message queuing on a single host - you would simply have your webapp push something to a queue that a continuously running console app would consume at the next suitable opportunity
beanstalkd - only found this one while writing this answer, but looks interesting
dropr is a PHP based message queue project, but hasn't been actively maintained since Sep 2010
php-enqueue is a recently (2017) maintained wrapper around a variety of queue systems
Finally, a blog post about using memcached for message queuing
Another, perhaps simpler, approach is to use ignore_user_abort - once you've sent the page to the user, you can do your final processing without fear of premature termination, though this does have the effect of appearing to prolong the page load from the user perspective.
When you just want to execute one or several HTTP requests without having to wait for the response, there is a simple PHP solution, as well.
In the calling script:
$socketcon = fsockopen($host, 80, $errno, $errstr, 10);
if($socketcon) {
$socketdata = "GET $remote_house/script.php?parameters=... HTTP 1.1\r\nHost: $host\r\nConnection: Close\r\n\r\n";
fwrite($socketcon, $socketdata);
fclose($socketcon);
}
// repeat this with different parameters as often as you like
On the called script.php, you can invoke these PHP functions in the first lines:
ignore_user_abort(true);
set_time_limit(0);
This causes the script to continue running without time limit when the HTTP connection is closed.
Another way to fork processes is via curl. You can set up your internal tasks as a webservice. For example:
http://domain/tasks/t1
http://domain/tasks/t2
Then in your user accessed scripts make calls to the service:
$service->addTask('t1', $data); // post data to URL via curl
Your service can keep track of the queue of tasks with mysql or whatever you like the point is: it's all wrapped up within the service and your script is just consuming URLs. This frees you up to move the service to another machine/server if necessary (ie easily scalable).
Adding http authorization or a custom authorization scheme (like Amazon's web services) lets you open up your tasks to be consumed by other people/services (if you want) and you could take it further and add a monitoring service on top to keep track of queue and task status.
http://domain/queue?task=t1
http://domain/queue?task=t2
http://domain/queue/t1/100931
It does take a bit of set-up work but there are a lot of benefits.
If it just a question of providing expensive tasks, in case of php-fpm is supported, why not to use fastcgi_finish_request() function?
This function flushes all response data to the client and finishes the request. This allows for time consuming tasks to be performed without leaving the connection to the client open.
You don't really use asynchronicity in this way:
Make all your main code first.
Execute fastcgi_finish_request().
Make all heavy stuff.
Once again php-fpm is needed.
I've used Beanstalkd for one project, and planned to again. I've found it to be an excellent way to run asynchronous processes.
A couple of things I've done with it are:
Image resizing - and with a lightly loaded queue passing off to a CLI-based PHP script, resizing large (2mb+) images worked just fine, but trying to resize the same images within a mod_php instance was regularly running into memory-space issues (I limited the PHP process to 32MB, and the resizing took more than that)
near-future checks - beanstalkd has delays available to it (make this job available to run only after X seconds) - so I can fire off 5 or 10 checks for an event, a little later in time
I wrote a Zend-Framework based system to decode a 'nice' url, so for example, to resize an image it would call QueueTask('/image/resize/filename/example.jpg'). The URL was first decoded to an array(module,controller,action,parameters), and then converted to JSON for injection to the queue itself.
A long running cli script then picked up the job from the queue, ran it (via Zend_Router_Simple), and if required, put information into memcached for the website PHP to pick up as required when it was done.
One wrinkle I did also put in was that the cli-script only ran for 50 loops before restarting, but if it did want to restart as planned, it would do so immediately (being run via a bash-script). If there was a problem and I did exit(0) (the default value for exit; or die();) it would first pause for a couple of seconds.
Here is a simple class I coded for my web application. It allows for forking PHP scripts and other scripts. Works on UNIX and Windows.
class BackgroundProcess {
static function open($exec, $cwd = null) {
if (!is_string($cwd)) {
$cwd = #getcwd();
}
#chdir($cwd);
if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
$WshShell = new COM("WScript.Shell");
$WshShell->CurrentDirectory = str_replace('/', '\\', $cwd);
$WshShell->Run($exec, 0, false);
} else {
exec($exec . " > /dev/null 2>&1 &");
}
}
static function fork($phpScript, $phpExec = null) {
$cwd = dirname($phpScript);
#putenv("PHP_FORCECLI=true");
if (!is_string($phpExec) || !file_exists($phpExec)) {
if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
$phpExec = str_replace('/', '\\', dirname(ini_get('extension_dir'))) . '\php.exe';
if (#file_exists($phpExec)) {
BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
}
} else {
$phpExec = exec("which php-cli");
if ($phpExec[0] != '/') {
$phpExec = exec("which php");
}
if ($phpExec[0] == '/') {
BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
}
}
} else {
if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
$phpExec = str_replace('/', '\\', $phpExec);
}
BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
}
}
}
PHP HAS multithreading, its just not enabled by default, there is an extension called pthreads which does exactly that.
You'll need php compiled with ZTS though. (Thread Safe)
Links:
Examples
Another tutorial
pthreads PECL Extension
UPDATE: since PHP 7.2 parallel extension comes into play
Tutorial/Example
reference manual
This is the same method I have been using for a couple of years now and I haven't seen or found anything better. As people have said, PHP is single threaded, so there isn't much else you can do.
I have actually added one extra level to this and that's getting and storing the process id. This allows me to redirect to another page and have the user sit on that page, using AJAX to check if the process is complete (process id no longer exists). This is useful for cases where the length of the script would cause the browser to timeout, but the user needs to wait for that script to complete before the next step. (In my case it was processing large ZIP files with CSV like files that add up to 30 000 records to the database after which the user needs to confirm some information.)
I have also used a similar process for report generation. I'm not sure I'd use "background processing" for something such as an email, unless there is a real problem with a slow SMTP. Instead I might use a table as a queue and then have a process that runs every minute to send the emails within the queue. You would need to be warry of sending emails twice or other similar problems. I would consider a similar queueing process for other tasks as well.
It's a great idea to use cURL as suggested by rojoca.
Here is an example. You can monitor text.txt while the script is running in background:
<?php
function doCurl($begin)
{
echo "Do curl<br />\n";
$url = 'http://'.$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI'];
$url = preg_replace('/\?.*/', '', $url);
$url .= '?begin='.$begin;
echo 'URL: '.$url.'<br>';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($ch);
echo 'Result: '.$result.'<br>';
curl_close($ch);
}
if (empty($_GET['begin'])) {
doCurl(1);
}
else {
while (ob_get_level())
ob_end_clean();
header('Connection: close');
ignore_user_abort();
ob_start();
echo 'Connection Closed';
$size = ob_get_length();
header("Content-Length: $size");
ob_end_flush();
flush();
$begin = $_GET['begin'];
$fp = fopen("text.txt", "w");
fprintf($fp, "begin: %d\n", $begin);
for ($i = 0; $i < 15; $i++) {
sleep(1);
fprintf($fp, "i: %d\n", $i);
}
fclose($fp);
if ($begin < 10)
doCurl($begin + 1);
}
?>
There is a PHP extension, called Swoole.
Although it might not be enabled, it is available on my hosting for being enabled at click of a button.
Worth checking it out. I haven't had time to use it yet, as I was searching here for info, when I stumbled across it and thought it worth sharing.
Unfortunately PHP does not have any kind of native threading capabilities. So I think in this case you have no choice but to use some kind of custom code to do what you want to do.
If you search around the net for PHP threading stuff, some people have come up with ways to simulate threads on PHP.
If you set the Content-Length HTTP header in your "Thank You For Registering" response, then the browser should close the connection after the specified number of bytes are received. This leaves the server side process running (assuming that ignore_user_abort is set) so it can finish working without making the end user wait.
Of course you will need to calculate the size of your response content before rendering the headers, but that's pretty easy for short responses (write output to a string, call strlen(), call header(), render string).
This approach has the advantage of not forcing you to manage a "front end" queue, and although you may need to do some work on the back end to prevent racing HTTP child processes from stepping on each other, that's something you needed to do already, anyway.
If you don't want the full blown ActiveMQ, I recommend to consider RabbitMQ. RabbitMQ is lightweight messaging that uses the AMQP standard.
I recommend to also look into php-amqplib - a popular AMQP client library to access AMQP based message brokers.
Spawning new processes on the server using exec() or directly on another server using curl doesn't scale all that well at all, if we go for exec you are basically filling your server with long running processes which can be handled by other non web facing servers, and using curl ties up another server unless you build in some sort of load balancing.
I have used Gearman in a few situations and I find it better for this sort of use case. I can use a single job queue server to basically handle queuing of all the jobs needing to be done by the server and spin up worker servers, each of which can run as many instances of the worker process as needed, and scale up the number of worker servers as needed and spin them down when not needed. It also let's me shut down the worker processes entirely when needed and queues the jobs up until the workers come back online.
i think you should try this technique it will help to call as many as pages you like all pages will run at once independently without waiting for each page response as asynchronous.
cornjobpage.php //mainpage
<?php
post_async("http://localhost/projectname/testpage.php", "Keywordname=testValue");
//post_async("http://localhost/projectname/testpage.php", "Keywordname=testValue2");
//post_async("http://localhost/projectname/otherpage.php", "Keywordname=anyValue");
//call as many as pages you like all pages will run at once independently without waiting for each page response as asynchronous.
?>
<?php
/*
* Executes a PHP page asynchronously so the current page does not have to wait for it to finish running.
*
*/
function post_async($url,$params)
{
$post_string = $params;
$parts=parse_url($url);
$fp = fsockopen($parts['host'],
isset($parts['port'])?$parts['port']:80,
$errno, $errstr, 30);
$out = "GET ".$parts['path']."?$post_string"." HTTP/1.1\r\n";//you can use POST instead of GET if you like
$out.= "Host: ".$parts['host']."\r\n";
$out.= "Content-Type: application/x-www-form-urlencoded\r\n";
$out.= "Content-Length: ".strlen($post_string)."\r\n";
$out.= "Connection: Close\r\n\r\n";
fwrite($fp, $out);
fclose($fp);
}
?>
testpage.php
<?
echo $_REQUEST["Keywordname"];//case1 Output > testValue
?>
PS:if you want to send url parameters as loop then follow this answer :https://stackoverflow.com/a/41225209/6295712
PHP is a single-threaded language, so there is no official way to start an asynchronous process with it other than using exec or popen. There is a blog post about that here. Your idea for a queue in MySQL is a good idea as well.
Your specific requirement here is for sending an email to the user. I'm curious as to why you are trying to do that asynchronously since sending an email is a pretty trivial and quick task to perform. I suppose if you are sending tons of email and your ISP is blocking you on suspicion of spamming, that might be one reason to queue, but other than that I can't think of any reason to do it this way.