I have been looking for several answers around the web and here, but I could not find one that solved my problem.
I am making several JQuery ajax calls to the same PHP script. In a first place, I was seeing each call beeing executed only after the previous was done. I changed this by adding session_write_close() to the beginning of the script, to prevent PHP from locking the session to the other ajax calls. I am not editing the $_SESSION variable in the script, only reading from it.
Now the behaviour is better, but instead of having all my requests starting simultaneously, they go by block, as you can see on the image:
What should I do to get all my requests starting at the same moment and actually beeing executed without any link with the other requests ?
For better clarity, here is my js code:
var promises = [];
listMenu.forEach(function(menu) {
var res = sendMenu(menu);//AJAX CALL
promises.push(res);
});
$.when.apply(null, promises).done(function() {
$('#ajaxSpinner').hide();
listMenu = null;
});
My PHP script is just inserting/updating data, and start with:
<?php
session_start();
session_write_close();
//execution
I guess I am doing things the wrong way. Thank you in advance for you precious help !!
Thomas
This is probably a browser limitation, there is a maximum number of concurrent connections to a single server per browser instance. In Chrome this has been 6, which reflects the size of the blocks shown in your screenshot. Though this is from 09, I believe it's still relevant: https://bugs.chromium.org/p/chromium/issues/detail?id=12066
Related
Below is the code that i am end up with using successful comet implementation.
$lastmodif = isset($this->params['form']['timestamp']) ? $this->params['form']['timestamp'] : 0;
$currentmodif = $already_updated[0]['Update']['lastmodified'];
while ($currentmodif <= $lastmodif)
{
usleep(5000000);
clearstatcache();
$already_updated_new = $this->Update->find('all',array
(
'conditions' => array
(
'Update.receiver_id' => $this->Auth->user('id'),
'Update.table_name' => "request_responses"
)
));
$currentmodif = $already_updated_new[0]['Update']['lastmodified'];
}
$already_updated[0]['Update']['lastmodified'] is the query result for get last updated timestamp of table.
In above code $lastmodif and $currentmodif is the timestamp that is being passed after every successful comet response.
But now problem is that when i am clicking on other links on same page nothing happens but after wait for so long its redirecting.
i think usleep is blocking other HTTP request.
i am using mysql and cakephp please guys guide me what should i do in order to solve this issue.
I have tried to flush when page is called but it shows can not modify header error as output is already sent.
Thanks.
I've met similar situation several times. It looks like Session is blocked by your sleeping script.
How to solve it in CakePHP:
call session_write_close(); at the start of your script.
There is no way to do that via Cake's Session Component or Helper
Note: If something inside script uses session - Cake will reopen session and hang all requests that use same session again. In this case you will need to close session before sleep or before any operations that take a lot of time to be finished
If your script uses sessions then you could notice such behavior. PHP locks the session file until the script completes.
This means that once a script starts a session, any other script that attempts to start a session using same session id is blocked until the previous script releases the lock (or terminates).
The workaround for this is to unlock the session before any lengthy process:
call session_start()
read/write any session variables
call session_write_close()
do lengthy processing
Yes, the usleep is blocking further requests. Depending on your hosting environment, you probably have a limited amount of processes available. I assume you have multiple users in your chat -> they all issue blocking processes unless none is available, that's why your other "links" timeout.
I would suggest to implement the wait on the client-browser side, eg
setTimeout(function() {
fetchAndPrintTheNewChats();
}, 50000000);
Any approach to do this within your PHP code will result in the same problem.
Can you share what version of cakephp you are using in case someone else who comes along might have a solution?
Cake has a session component: http://book.cakephp.org/2.0/en/core-libraries/components/sessions.html
and a session helper: http://book.cakephp.org/2.0/en/core-libraries/helpers/session.html
I have a JavaScript functions which calls a PHP function through AJAX.
The PHP function has a set_time_limit(0) for its purposes.
Is there any way to stop that function when I want, for example with an HTML button event?
I want to explain better the situation:
I have a php file which uses a stream_copy_to_stream($src, $dest) php function to retrieve a stream in my local network. The function has to work until I want: I can stop it at the end of the stream or when I want. So I can use a button to start and a button to stop. The problem is the new instance created by the ajax call, in fact I can't work on it because it is not the function that is recording but it is another instance. I tried MireSVK's suggest but it doesn't worked!
Depending on the function. If it is a while loop checking for certain condition every time, then you could add a condition that is modifiable from outside the script (e.g. make it check for a file, and create / delete that file as required)
It looks like a bad idea, however. Why you want to do it?
var running = true;
function doSomething(){
//do something........
}
setInterval(function(){if(running){doSomething()}},2000); ///this runs do something every 2 seconds
on button click simply set running = false;
Your code looks like:
set_time_limit(0);
while(true==true){//infinite loop
doSomething(); //your code
}
Let's upgrade it
set_time_limit(0);
session_start();
$_SESSION['do_a_loop'] = true;
function should_i_stop_loop(){
#session_start();
if( $_SESSION['do_a_loop'] == false ) {
//let's stop a loop
exit();
}
session_write_close();
}
while(true==true){
doSomething();
should_i_stop_loop(); //your new function
}
Create new file stopit.php
session_start();
$_SESSION['do_a_loop'] = false;
All you have to do now is create a request on stopit.php file (with ajax or something)
Edit code according to your needs, this is point. One of many solutions.
Sorry for my English
Sadly this isn't possible (sort of).
Each time you make an AJAX call to a PHP script the script spawns a new instance of itself. Thus anything you send to it will be sent to a new operation, not the operation you had previously started.
There are a number of workarounds.
Use readystate 3 in AJAX to create a non closing connection to the PHP script, however that isn't supported cross browser and probably won't work in IE (not sure about IE 10).
Look into socket programming in PHP, which allows you to create a script with one instance that you can connect to multiple times.
Have PHP check a third party. I.E have one script running in a loop checking a file or a database, then connect to another script to modify that file or database. The original script can be remotely controlled by what you write to the file/database.
Try another programming language (this is a silly option, but I'm a fan of node). Node.js does this sort of thing very very easily.
I have a counter timer and I tried to block a simple bypass to download without waiting.
so in main class I declared the boolean
$allow_download = false;
and in Javascript when the time is elapsed
else
{
textDLShow.style.display = 'none';
divDLShow.style.display = '';
"<?php $allow_download = true;?>";
}
and in the second class
if($allow_download == false)
echo "Test";
well, when time is elapsed the boolean is not set with positive value. Any suggestions ??
Thanks for your time !!
JavaScript cannot set the value of a PHP variable since the JavaScript interpreter cannot parse PHP (nor is the variable in the same interpreter anyway, since the JavaScript is run on the client's browser rather than on the server.)
In order to do this you will need to make a new request with JavaScript that your PHP code can read in order to set $allow_download to true and then serve up the download.
You'll want to read up on ajax, document.createElement (because one way to do this might be to create an iframe pointing at the download location after the time has elapsed) and setTimeout.
PHP is run on your server, the variables you create are no longer in scope when your client side javascript runs. There is no way to fix this unless you want to cook up some heavier stuff like storing in a database which IP addresses can download which files at what time.
php can run javascript, but javascript can never run php, take it for granted
the best thing you can do is run an ajax script to kind of call the php on the background
but really why bother going with all that, you can include the javascript in a php function and let it do the job
i have a php script that accepts a POST request as a listener to a web service then process all the data to two final arrays,
I'm looking for a way to initiate a second script that GET's those serialized arrays and do some more processing.
include() will not be good for me since i actually want to "free" or "end" the first script after passing the data
your help is much appreciated as always :)
EDIT - OK so looks like queue might be the solution! i never did anything like this before any examples or reference?
Does it need to happen immediately? Otherwise you could set up a cronjob that does that every X minutes. You'll have to make some kind of queue in which your first script sticks "requests" to the second script. The cronjob then processes the requests in the queue.
You should get into the habit of writing php scripts that are just a collection of functions (no auto-ran scripts, per se). This way you can include a script file at the top of the script your talking about and then call the function that does what you want.
For instance:
<?php
include('common_functions.php');
$array_1 = whatever_you_do_with_post_values();
$array_2 = other_thing_you_do_with_post_values();
// this function is located in 'common_functions.php'
do_stuff_with_arrays($array_1,$array_2);
?>
In Fact:
Just to be consistent with what I'm saying:
<?php
include('common_functions.php');
do_your_stuff();
function do_your_stuff() {
$array_1 = whatever_you_do_with_post_values();
$array_2 = other_thing_you_do_with_post_values();
// this function is located in 'common_functions.php'
do_stuff_with_arrays($array_1,$array_2);
}
?>
Obviously you should use better function & variable names, haha.
I'd do it all in one request. It cuts down on latency and makes the whole operation more efficient.
Remember you can have a long running request, but still service other requests. Apache will just spawn another php process to handle the other request from the webservice even though the first has not completed. As long as the script doesn't lock a shared resource (database file etc) this will work just fine.
That said, you should use cURL to call the second script. then post the unserialized array. cUrl will handle the rest.
If I'm generating a stream of data to send out to a browser, and the user closes the browser, can I tell within PHP that I don't need to bother generating or sending the rest of the stream? I'd like to insert something into this loop:
while (!feof($pipes[1])) {
echo fgets($pipes[1]);
}
My fallback plan is to have the browser use a JavaScript onunload to hit another PHP page to kill the process that's generating the data, but it would be cleaner if PHP could tell when I'm echoing to nowhere.
By default PHP will abort the script if the user navigates away. There are however times where you don't want this to happen so php has a config you set called ignore_user_abort.
http://php.net/manual/en/misc.configuration.php
There's also a function called register_shutdown_function() that is supposedly executed when execution halts. I've never actually used it, so I won't vouch for how well it works, but I thought I'd mention it for completeness.
I believe that script will automatically abort when loaded normally (No ajax). But if you want to implement some sort of long polling via php using xmlhttprequest I think you will have to do it with some sort of javascript because then php can't detect it. Also like to know the precise case.
These answers pointed me towards what I was looking for. The underlying process needed special attention to kill it. I needed to jump out of the loop. Thanks again, Stack Overflow.
while (!feof($pipes[1]) && !connection_aborted())
{
echo fgets($pipes[1]);
}
if (connection_aborted())
{
exec('kill -4 '.$mypid);
}