I was implementing the server-push content using comet to the client browser.
There should be updates when mysql got insert then something will happen to client, so I'm currently doing by PHP like this:
PHP
while (check database if update is there)
{
usleep(10000);
// do write json
}
It actually working, but what happening to me is my hosting(shared) run out of resource even when I just test with 5 simultaneous clients.
CPU is 40% loading at this moment and cause account disable.
So please someone advise any idea how to trigger php to send out the new update only without looping check.
I think your problem is that you have a slight error regarding usleep. The parameter should be:
micro seconds
Halt time in micro seconds. A micro second is one millionth of a
second.
Your script currently halts for 0.01 seconds instead of 10 seconds, which, I assume, is not what you wanted.
use:
usleep(10 * 1000000);
or:
sleep(10);
I don't know how your Javascript looks like, but I think you're approaching it incorrect. What you really wanna do is probably to send requests from the browser with 10 secs intervals. See this example.
This method will not use any CPU during the sleep time:
set_time_limit(0);
while (check database if update is there) {
sleep(10);
// do write json
}
Related
I'm using the DigitalOcean API to create droplets when my web application needs the extra resources. Because of the way DigitalOcean charges (min. one hour increments), I'd like to keep a created server on for an hour so it's available for new tasks after the initial task is completed.
I'm thinking about formatting my script this way:
<?php
createDroplet($dropletid);
$time = time();
// run resource heavy task
sleep($time + 3599);
deleteDroplet($dropletid);
Is this the best way to achieve this?
It doesn't look like a good idea, but the code is so simple, nothing can compete with that. You would need to make sure your script can run, at least, for that long.
Note that sleep() should not have $time as an argument. It sleeps for the given number of seconds. $time contains many, many seconds.
I am worried that the script might get interrupted, and you will never delete the droplet. Not much you can do about that, given this script.
Also, the sleep() itself might get interrupted, causing it to sleep much shorter than you want. A better sleep would be:
$remainingTime = 3590;
do {
$remainingTime = sleep($remainingTime);
} while ($remainingTime > 0);
This will catch an interrupt of sleep(). This is under the assumption that FALSE is -1. See the manual on sleep(): http://php.net/manual/en/function.sleep.php
Then there's the problem that you want to sleep for exactly 3599 seconds, so that you're only charged one hour. I wouldn't make it so close to one hour. You have to leave some time for DigitalOcean to execute stuff and log the time. I would start with 3590 seconds and make sure that always works.
Finally: What are the alternatives? Clearly this could be a cron job. How would that work? Suppose you execute a PHP script every minute, and you have a database entry that tells you which resource to allocate at a certain start time and deallocate at a certain expire time. Then that script could do this for you with an accurary of about a minute, which should be enough. Even if the server crashes and restarts, as long as the database is intact and the script runs again, everything should go as planned. I know, this is far more work to implement, but it is the better way to do it.
Wanted to know if there was a was to prevent a php timeout of occurring if a part of the code has started being process.
Let me explain:
i have a script that is executed that take way too long to even use
ini_set('max_execution_time', 0);
set_time_limit(0);
the code is built to allow it to timeout and restart where it was but I have 2 line of code that need to be executed together for that to happen
$email->save();
$this->_setDoneWebsiteId($user['id'], $websiteId);
is there a way in php to tell it it has to finish executing them both even if the timeout is called?
Got an idea as I'm writing this, i could use a time_out of 120 sec and start a timer and if there is less then 20 sec left before timeout to stop, i just wanted to know if i was missing something.
Thank you for your inputs.
If your code is not synchronous and some task takes more than 100 seconds - you'll not be able to check the execution time.
I see only one truly HACK (be careful, test it with php -f in console for be able to kill the processes):
<?php
// Any preparations here
register_shutdown_function(function(){
if (error_get_last()) { // There was timeout exceeded error
// Call the rest of your system
// But note: you have no stack, no context, no valid previous frame - nothing!
}
});
One thing you could do is use the DATE time features to monitor your average execution time. (kind of builds up with each execution assuming you have a loop).
If the average then time is then longer than how ever much time you have left (you would be counting how much time has been taken already against your maximum execution time), you would trigger a restart and let it pick up from where it left off.
How ever if you are experiencing time outs, you might want to look at ways to make your code more efficient.
No, you can't abort timeout handler, but i'd say that 20 seconds is quite a big time if you're not parsing something huge. However, you can do the following:
Get time of the execution start ($start = $_SERVER['REQUEST_TIME'] or just $start = microtime(true); in the beginning of your controller).
Asset that execution time is lesser than 100 seconds before running $email->save() or halt/skip code if necessary. This is as easy as if (microtime(true) - $start < 100) { $email->save()... }. You would like more abstraction on this, however.
(if necessary) check execution time after both methods have ran and halt execution if it has timed out.
This will require time_limit set to big value or even turned off and tedious work to prevent too long execution. In most cases timeout is your friend that just tells you're work is taking too much time and you should rethink your architecture and inner processes; if you're out of 120 seconds, you'll probably want to put that work on a daemon.
Thank you for your input, as I thought the timer solution is the best way.
what I ended up doing was the following, this is not the actual code as its too long to make a good answer but just the general idea.
ini_set('max_execution_time', 180);
set_time_limit(180);
$startTime = date('U'); //give me the current timestamps
while(true){
//gather all the data i need for the email
//I know its overkill to break the loop with 1 min remaining
//but i realy dont want to take chances
if(date('U') < ($startTime+120)){
$email->save();
$this->_setDoneWebsiteId($user['id'], $websiteId);
}else{
return false
}
}
I could not use the idea of measuring the average time of each cycle as it vary too much.
I could have made the code more efficient but it number of cycle is based on the number of users and websites in the framework. It should grow big enough to need multiple run to be completed anyway.
Il have to make some research to understand register_shutdown_function, but I will look into it.
Again Thank you!
I set up a very small (internal) dedicated web server, and I need to pull some energy data every 10 seconds or so from an XML file. This is the PHP code I have thus far:
<?php
$mydata = simplexml_load_file('http://192.168.x.xx:yyy/data.xml');
echo $mydata->device[0]->name;
echo $mydata->device[0]->value;
?>
I tested similar code out on my web server and PHP is installed and I think this should work, but I'd like to have this run every 10 seconds or so. This way the data displaying on my web page is always up to date. The web page will be left running 24/7 as a sign on the wall. What's the easiest way to refresh the data?
I would simply refresh the portion of the web page that displays the data using Ajax. Trigger the refresh using a JavaScript timer.
The easiest way? Add this line to your page.
<meta http-equiv="refresh" content="10">
This may not be the best way though, especially if you have a lot of stuff on the page that you don't need reloaded every 10 seconds. If that's the case, you should look into AJAX.
If you have a page setup that returns only the data you need (like your example) you can make an asynchronous request every 10 seconds using JavaScript's setInterval() to get the latest data and show it.
If you are running this through a browser then I would go with Eric's answer.
However if you have this running from command line you can do one of the two:
Have your current script say pull_energy_data.php to run from a cron job every 10 seconds. Don't forget to create some sort of locking mechanism. Just in case the job takes more than 10 seconds to run and you'll have more than one script running at the same time.
Another approach is having a script wrapping your pull_energy_data.php running in a loop and executing it every 10 seconds. This is less desirable than the previous approach as you'll need to keep track of when pull_energy_data.php last ran and how to issue a command to stop the wrapper script.
assuming you are running the server in Linux/Unix, perhaps look into writing a cronjob (automated job) for it?
One solution I can think of is to run the PHP script as a cronjob every 10 seconds, writing the output into a file or a database table.
You can then write a separate PHP script that reads the contents of the file/DB entry whenever anyone loads it in a browser.
I'm pretty sure I've seen this done in a php script once, although I cant find the script. It was some script that would automatically check for updates to that script, and then replace itself if there was an update.
I don't actually need all that, I just want to be able to make my PHP script automatically run every 30 minutes to an hour, but I'd like to do it without cronjobs, if its possible.
Any suggestions? Or is it even possible?
EDIT: After reading through a possible duplicate that RC linked to, I'd like to clarify.
I'd like to do this completely without using resources outside of the PHP script. AKA no outside cronjobs that send a GET request. I'd also like to do it without keeping the script running constantly and sleeping for 30 minutes
If you get enough hits this will work...
Store a last update time somewhere(file, db, etc...). In a file that gets enough hits add a code that checks if the last update time was more xx minutes ago. If it was then run the script.
You may want to use the PHP's sleep function with specified time to run your code with that interval or you may want to try some online cron job services if you wish.
Without keeping the script running constantly, you'll either have to use something hackish that's not guaranteed to actually run (using regular user pages accesses to run a side routine to see if X amount of time has passed since last run of the script and if so, run it again), or use an external service like cron. There's no way for a regular PHP script to just magically invoke itself.
You can either use AJAX calls from your real visitors to run scheduled jobs in the background (google for "poor man's cron", there are a number of implementations out there) or use some external cron-like service (for example a cronjob on some other machine). In theory you could just run a PHP script with no timeout and make it loop forever and fire off requests at the appropriate time, but the only thing that would achieve is reinventing cron in a very ineffective and fragile way (if the script dies for some reason, it will never start again on its own, while cron would just call it again).
Either way, you will need to set proper execution time so the script does not exceed it.
I found this:
<?php
// name of your file
$myFile="time.db";
$time=file($myFile);
if(time()-3600 > $time[0]){
// an hour has elapsed
// do your thing.
// write the new timestamp to file
$fh = fopen($myFile, 'w') or die("can't open file");
fwrite($fh, time());
fclose($fh);
}
else{
// it hasn't been an hour yet, so do nothing
}
?>
in here
If the host includes a mysql 5.1+ db then perhaps timed triggers are availible to call the script? I like these mission impossible type questions, but need more information on what kind of playground and rules for the best answer.
I need to create a script in PHP language which performs permutation of numbers. But PHP has an execution time limit set to 60 seconds. How can I run the script so that if you need to run more than 60 sesunde, not been interrupted by the server. I know I can change the maximum execution time limit in php, but I want to hear another version that does not require to know in advance the execution time of a script.
A friend suggested me to sign in and log out frequently from the server, but I have no idea how to do this.
Any advice is welcome. An example code would be useful.
Thanks.
First I need to enter a number, lets say 25. After this the script is launch and it need to do the following: for every number <= than 25 it will create a file with the numbers generated at the current stage; for the next number it will open the previuos created file, and will create another file base on the lines of the opened file and so on. Because this take to long, I need to avoid the script beeing intrerupted by the server.
#emanuel:
I guess when your friend told you "A friend suggested me to sign in and log out frequently from the server, but I have no idea how to do this.", he/she must have meant "Split your script computation into x pieces of work and run it separately"
For example with this script you can execute it 150 times to achieve a 150! (factorising) and show the result:
// script name: calc.php
<?php
session_start();
if(!isset($_SESSION['times'])){
$_SESSION['times'] = 1;
$_SESSION['result'] = 0;
}elseif($_SESSION['times'] < 150){
$_SESSION['times']++;
$_SESSION['result'] = $_SESSION['result'] * $_SESSION['times'];
header('Location: calc.php');
}elseif($_SESSION['times'] == 150){
echo "The Result is: " . $_SESSION['result'];
die();
}
?>
BTW (#Davmuz), you can only use set_time_limit() function on Apache servers, it's not a valid function on Microsoft IIS servers.
set_time_limit(0)
You could try to put the calls you want to make in a queue, which you serialize to a file (or memory cache?) when an operation is done. Then you could use a CRON-daemon to execute this queue every sixty seconds, so it continues to do the work, and finishes the task.
The drawbacks of this approach are problems with adding to the queue, with file locking and the such, and if you need the results immediately, this can prove troublesome. If you are adding stuff to a Db, it might work out. Also, it is not very efficient.
Use set_time_limit(0) but you have to disable the safe_mode:
http://php.net/manual/en/function.set-time-limit.php
I suggest to use a fixed time (set_time_limit(300)) because if there is a problem in the script (endless loops or memory leaks) this can not be a source of problems.
The web server, like Apache, have also a maximum time limit of 300 seconds, so you have to change it. If you want to do a Comet application, it may be better to chose another web server than Apache that can have long requests times.
If you need a long execution time for a heavy algorithm, you can also implement a parallel processing: http://www.google.com/#q=php+parallel+processing
Or store the input data and computer with another external script with a cron or whatever else.