Seeing some strange behavior in my application. Any time I have a long running script waiting for a response in the browser, any other page in the application will spin/hang after a click (even for very simple//static pages) until the original page finishes loading. This is a PHP5.3 based application using native PHP sessions on Apache 2.2.x.
This happens in multiple browsers in all our dev, qa, and production instances. I'm not sure where to start looking. Any advice?
Get all the data you need from the $_SESSION, and call session_write_close() before you are going to do something that takes a long time. Due to a PHP script still being active with that session, it locks the session (after all, it may write some data to that session that the next request needs).
If you need to write something to the session after you've done your long job, you can just call session_start() once again (provided you've not generated output yet), write to it, and after that the script may end, or maybe you repeat this cycle a few times.
Also, don't call session_start() if you don't need it, I see you mention 'static' pages. If a page does not need session data, avoid the overhead & locks it creates.
I have ocassionally detected a strange problem with PHP sessions.
When I am running two PHP scripts using SAME session ID, second script is stuck until first one is completed.
I guess it is because trying to open same session storage file twice. But possible I am not right.
You will never catch this effect in normal site work, because user usually didn't open two or more pages simultaneously.
However, if you try to get content of a page of the same site using file_get_contents(), you will catch this issue.
Additionally, I have copying my cookies through context, so file_get_contents() trying to re-open same session as already opened in calling script.
As result, I have stucked long-running script (about 5-10 mins) which also disables me to open any new page of same site using same sessionid / login.
How I can to resolve this issue? Did you ever see any beautiful solution for it?
Yes, this is called "session locking" and is normal in PHP.
One solution is not not use sessions, just set cookies for your required persistent information.
Another solution is to implement your own session handler:
http://php.net/manual/en/session.customhandler.php
A detailed walkthrough about custom MySQL session handlers is here:
http://phpmaster.com/writing-custom-session-handlers/
I also found quite simple solution for this problem. We can use session_write_close(); to unlock session file in script 1, then we can make any file_get_contents(), curl_exec() etc without any worries and after these operations turn session back by session_start(). Checked by myself, works as charm!
I´m having some serious trouble debugging this particular problem and I hope someone has a clue what i´m doing wrong.
I have a Custom CMS system working that uses Paragraphs as building blocks that get updated using Ajax(prototypejs) calls and functions that parse the HTML chunks in given order, clean them up and save this data in associative arrays in a Session variable.
Users log in, Session is created and I can check for this session without problem in every page I need it. The system works directly on the definitive websites, so the user can see his updates on realtime and browse the site as a normal user would do, but editing.
So, nothing new here. But here is the weird thing.
Enduser site on edit mode(admin user logged in): path "/"
After the logged status is verified, a function processes the editable content and saves an associative array to session, it also starts some javascript objects for editing every paragraph. Data is actually saved, I can use an external script to check if it´s there after this php script ends.If I load a new page(new content), Session gets updated with new data)
Admin User modifies a paragraph using an Inplaceeditor and this HTML chunk is send via Ajax to a php script that starts the named session, reads the present session data, checks if a paragraph should be modified, appended or deleted and reassigns values to existing array keys in $_SESSION. if i make a var_dump() o print_r to $_SESSION after assigning new data is there.After that the script echoes the processed html, and ajax updates the original paragraph on the calling page.
This script is in /admin/cms/...etc, that means at least 4 directories inside the root of the site.
When the script ends, I check using the same session dump script to see if data was really written/commited, but no, $_SESSION has only the original data from the calling page.
Same ID, same session name, same session_start() but no data gets written.
This whole operation is very quick, so I though it could be a speed problem, scripts ends before session_write_close can make his work.
But if I add a new key to $_SESSION array and put some data there, data gets updated and written. If i don´t output anything on this script and just process data and set session variables it also get´s updated and written.
It´s like some members of $_SESSION array are getting blocked to update.
What i did to track this error and what i´m sure i´m not doing wrong.
1.- register_globals are off of course
2.- session_name() and session_start() are always present and in the given
order. I used to have multiple
session_start() -close on a same page
to use several named sessions, but to
refine the problem this is not longer
so.
3.- I use session_write_close() after session data is processed. Also
tried without, letting php decide
when to commit data, but no luck.
4.- I`m using only cookies for SID.
5.- sessions are stored on /tmp, i can see the data getting updated.
I also tried using a custom save
handler on DB, but same problem,
"_write" got only called when no output as present.
I searched php.net, stackoverflow, google, etc for this subject. I never ask without investigation, this is my first time in many years...but it´s just so unlogical it must be something tiny a haven´t thought of.
The most weird thing is that when I just process data without output $_SESSION gets updated ok. But if i modify this script afterwards by adding the output and try again, instead of just having the new(last) value present I get the original value back, the one created by the calling page at first place, sometimes after playing around a few times! PHP can´t cache values between scripts or?I dont have globlals on.
I´m really clueless. This system worked flawless on PHP4.3, since i´m using 5.3.3 for two moths my users where caliming data where getting mixed up, so i checked and yes, there are serious problems. Today I updated to (5.3.6) and I can´t get this session values commited.
Script code called via Ajax:
<?
session_cache_limiter('nocache');
session_name("CMS_ses");
session_start();
include('../htmLawed/htmLawed.php');
include("utils_cms.php");
include("../../../php/utils_array.php");
$value=$_POST['value'];
$editorId=$_POST['editorId'];
$clase=$_POST['clase'];
$editorId=str_replace("pre","",$editorId);
$value=html_entity_decode(stripslashes($value),ENT_QUOTES);
if (strlen(trim($value))==0)
{
die();
}
$value="<div id=\"$editorId\" class=\"$clase\">$value</div>";
$newXHTML=$value;
$retorno=CMS_nuevoBloque($newXHTML,$editorId);
$_SESSION['data']['CMSeditores']=$retorno[1];
$_SESSION['data']['CMScont']=$retorno[2];
session_write_close();
print_r($retorno[0]); //Offending part...without everything works
?>
really nothing strange here....main page code is even simpler, no strange php directives, etc.
Here is the header of the caller page
include 'php/db.php';
$len=$_GET['len'];
$sec=$_GET['sec'];
$cont=$_GET['cont'];
$admfin=$_GET['admfin'];
$fecha=$_GET['fecha'];
$token=$_GET['token'];
$cur=$_GET['cur'];
$PHP_SELF=$_SERVER['PHP_SELF'];
session_cache_limiter('nocache');
session_name("CMS_ses");
session_start();
$passvar='';
unset($adm);
if ((!empty($_SESSION['cms_logged'])) and (!isset($admfin)) )
{
$nivelpermisos=$_SESSION['cms_logged_group'];
$useractual=$_SESSION['cms_logged'];
$adm=1;
}
elseif (empty($_SESSION['cms_logged']))
{
unset($useractual);
}
//.........rest of the code
UPDATE: I did late night tests and found someting i don´t understand.HElP please:
It has not only to do with Sessions but also with Mysql Querys. Same code, but instead of trying to write to $_SESSION array i made a simple update to a Innodb table using the session_id. When i Output some code, the update does get executed,(i can output the query string and no mysql_error() or notice) problems, but checking the database the row doesn´t get updated. Letting the output out if the script and Query does get commited. Only common thing is sessions are started and output is made.
I restarted Apache, etc(who knows) but no luck. Then i made something really stupid, because this is a server side thing. I changed my browser to Firefox(using safari) and everything works! Ok, recheck, back to safari, nothing works. Both running side by side, same issue. PHP is server side, how can different browsers handle code different, can a browser say to apache rollback, request not handled or call the same script twice without notice(checked safaris developer console and the script is called only once) ? Can safari resubmit data silently because it "thinks" ajax failed? I checked headers using firebug and Safaris developer tools , nothing strange but whenever i make a Ajax call with safari, the caller page reloads data(Aka conection to server...).
I really don´t understand nothing.
I had a similar problem to this (if I have understood correctly). I needed to force session data to be written (for a custom session driver) after scripts have finished running. A shutdown function can be registered which should run after scripts have finished.
Maybe this will solve (or help you to solve) your problem.
http://php.net/manual/en/function.register-shutdown-function.php
Thank's for your help. I was doing everything in the right order and still session data was not being written. Session names where necesary because sometimes we test many sites on the same domain using the same custom CMS. So, finally, after making lots of test and no luck, i found that register globals was active on this server(we never use it, code was written having this option off in mind of course), but it messes with sessions!. Switching this off made a huge change. No more problemas. I also made a custom session handler in DB, so i could track the problems in an more centralized way.
Conclussion: Never use register globals + named sessions, an complex data in sessions.
Anyway, i will give this issue more time and more tests. Ajax calls are also sometimes too fast, i had to put a sleep command so writing the session data was really done.Thanks
I am not sure but few suggestion i think may be helpful.
delete session cookies before refreshing the page for testing purposes :)
Ensure that you're not assigning any arrays with a key containing the pipe character (|). This will prevent the session data from being serialized and saved.
Do session_regenerate_id(true); many cases session_write_close doesn't seem to matter with out session_regenerate_id. or just do session_start() after session_write_close() if you are relying on SID ; and in your case i think this is what is causing problem to you as you are ending the current session every time and not re starting it for the next page. hope u get my point. Further more To Make sure data is actually flushed out to the browser use ob_end_flush();
i could not understand the connection between
$_SESSION['data']['CMSeditores']=$retorno[1];
$_SESSION['data']['CMScont']=$retorno[2];
and
$nivelpermisos=$_SESSION['cms_logged_group'];
$useractual=$_SESSION['cms_logged'];
i think you need to paste some more code where the data part is causing problem instead of admin login part.
i hope this helps you.:)
Is there any reason you're establishing the session name twice? I've had issues in the past where I would establish the session without a name, then another piece of script (not mine) was naming the session. Even at the end of the script I was able to print out the session variable, but once I went to a new page my session had been forgotten. It wasn't until I copied the name included in the 2nd script into my session call that it was solved.
Check that there's no other session names being used; also, maybe try only naming the session once, at the first call to the session?
Question: Are you calling session_start() first thing... before ANY output to the browser and before any variables are assigned?
Sounds silly but give it a try.
Also, why are you using session names? Really not necessary unless you have a lot of session variables with the same name serving different purposes and if thats the case then you need to fix that first!
I had a similar problem but it was having with ie few years back. IE manipulates the header on its own way and that causes strange php bugs that you can find in php.net archives.
#Diego Pino Navarro, please see this help page and find Safari and it's issues with php.
I also found "Safari "forget" http-authentication's logon-information".
I am trying to make some changes to an opensource project. I want to keep track of when users log in and log out.
Right now I change their login status in db when they login or manually log out. The problem right now is that I cannot find out if the user just closed their browser without pressing on logout button.
For this reason I need to trigger a function that will change database every time the user's session expires.
I've tried session_set_save_handler in PHP, but it looks like I need to override the whole session behavior. What I am looking for is to keep default session behavior and just add functionality when the user's session expires. Is there a way to do that?
I did something really nasty once. Every time a session was "updated" by a page refresh / fetch / etc., I updated a timestamp on a DB row. A second daemon polled the DB every 10 minutes and performed "clean-up" operations.
You won't find any native PHP facilities to achieve your goal. Session timeout doesn't run in the background. You won't even know if a session is timed out, unless a timed out session attempts another access. At this point, nearly impossible to trap, you can make your determination and handle it appropriately.
I'd recommend a queue & poll architecture for this problem. It's easy and will definitely work. Add memcached if you have concerns about transaction performance.
I presume you're using standard PHP file-based sessions. If that's the case, then PHP will do its own garbage collection of stale sessions based on the session.gc_* configuration parameters in php.ini. You can override those to disable the garbage collector completely, then roll your own GC script.
You could either check the timestamps on the files (quick and easy to do in a loop with stat()) to find 'old' sessions, or parse the data in each file to check for a variable that lists the last-access time. Either way, the session files are merely the output of serialize($_SESSION) and can be trivially re-loaded into another PHP instance.
What about window close event on javascript. So basically session is destroyed when all of the windows of the session site are closed. So, when the last window is closed ( this is checked via additional js checking ) send ajax request to server.
I need to perform an action after a session times out. However I have no clue how to trigger that action without an incoming request. An event handler/a listener/a timer would suit perfect but since PHP does not support such a thing it is really difficult to accomplish what I want.
After lot of searching I bumped into session_set_save_handler but I still cannot fully understand how this method works. If I write code that triggers the action inside the close method when it will be executed?
I also need to keep the current session solution as it is and I wonder what the ramifications of using session_set_save_handler in conjunction with that will be? (My current solution sets a session cookie, assigns a name to the session and starts the session, when the user logs out or a request is done after the session timeout (that value is set in a configuration file) the session is completely destroyed)
Regards!
This is somewhat difficult to do in php, AFAIK.
But you can try by making a passive session handler:
Store session ids associated with a timestamp.
Each time the user associated with certain id makes a request, refresh it's timestamp.
You can detect defunct sessions by comparing the system's current, and each session id's timestamps. The ones that differ above a given treshold (say 30min), are assumed to have passed away. Then you can execute your own save handlers for these session ids.
This won't work if the session end handler needs to be executed inmediately, as this process is executed each time when a request arrives (from any user), so it will depend directly on the website's traffic flow.
But you can also solve it by setting cron jobs each 15min or so. Depending on how expensive your save handlers are, seems an acceptable periodicity.
PHP needs to run in some way for PHP code to execute. Either through a user request or a cronjob.
A Session is saved to the locale storage when a PHP request finishes executing or when session_write_close() is called
This session_set_save_handler() allows you to write your own save handler.