Run PHP Task Asynchronously

Question

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  gt  dev null 2 gt  amp 1  amp       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

User · Answer

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.

User · Answer

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

User · Answer

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       lt  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                gt               lt  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                               gt    testpage php       lt       echo   REQUEST  Keywordname     case1 Output  gt  testValue       gt    PS if you want to send url parameters as loop then follow this answer  https   stackoverflow com a 41225209 6295712

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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- gt CurrentDirectory   str replace             cwd                WshShell- gt Run  exec  0  false             else               exec  exec      gt   dev null 2 gt  amp 1  amp                          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

User · Answer

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

User · Answer

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    lt  php  function doCurl  begin        echo  Do curl lt br   gt  n        url    http       SERVER  SERVER NAME     SERVER  REQUEST URI         url   preg replace                url        url      begin    begin      echo  URL     url   lt br gt         ch   curl init        curl setopt  ch  CURLOPT URL   url       curl setopt  ch  CURLOPT RETURNTRANSFER  true        result   curl exec  ch       echo  Result     result   lt br gt        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  lt  15   i              sleep 1           fprintf  fp   i   d n    i             fclose  fp       if   begin  lt  10          doCurl  begin   1        gt

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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- gt 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

User · Answer

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

[php] Run PHP Task Asynchronously

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