I am trying to create a site in PHP and MySQL where a person is assigned to do a task for another person. Time period allotted to complete the task is 72 hours.
If done, the other person will confirm so. If not, I want to take certain actions (like blocking his account, sending an email, assign the task to someone else etc.) What is the best way to do this?
As the count-down runs second-by-second, I guess I will have to run a script every second.
You could use a cronjob to check for the deadline and eventually send the email, block the account, etc...
Although, if you actually need a persecond precision, you might want to use a single process with an "infinite" cicle and some sleeps in between.
If your server is from *nix family, you could use cron/crontab. See examples of usage at: http://en.wikipedia.org/wiki/Cron and https://help.ubuntu.com/community/CronHowto
Very few things have to happen truely immediately. If you've waited 72 hours for something to happen, having an action occur within a matter of a few minutes will not matter so much.
If you really do want something to happen so quickly, and you will always have a long time between potential events, one thing I would suggest is not using a cronjob, but something more akin to what #muc has suggested - a script that runs regularly within a shell script that will keep it going (just doing an 'exec $0' at the end to rerun the script when it would exit).
The script (in PHP for example) that checks the database doesn't have to be running all the time either. Whenever it finds something that is due to happen in more than a few seconds time, it sleeps till the next event is due to happen. When it wakes up, it can double-check that it is still required, and then performs the relevant job.
<?php
$jobId = whatToRunNext();
if (! $jobId) {
exit;
}
$secsToNextJob = howLongToNextJob($jobId);
if ($secsToNextJob > 0) {
sleep($secsToNextJob);
if (! jobStillRequired($jobId)) {
exit;
}
}
doJob($jobId);
exit;
Wrap that in a shell sript that will keep it running, maybe with a small sleep in the bash script, and you'd be good - while not being in a very long-running, cpu-killing loop.
If I needed to do something like that, I would probably go by these steps:
Create event and calculate deadline
Set up a cronjob to run at the deadline time
cronjob checks the event status and takes actions
I think this will be the most efficient way in doing it.
I am trying to create a site in PHP and MySQL where a person is
assigned to do a task for another person. Time period allotted to
complete the task is 72 hours.
These could simply just be db vales
table_task
.id
.user_assigned
.strart_date
.end_date
.status
.desc
If done, the other person will confirm so. If not, I want to take
certain actions (like blocking his account, sending an email, assign
the task to someone else etc.) What is the best way to do this?
This again, Admin panel of some form with a layout of assigned jobs, the ''worker'' should be required to post a job as ''done'', the ''admin'' can then confirm this. This can all be managed via Values in the db ''table_task.status''
As the count-down runs second-by-second, I guess I will have to run a
script every second.
^-- server suicide
Run the cron ever hour at most. If you have 1000 users. Then this cron will run 1000 a sec
in an hour this is, 60000*60
If you need to display the time use some jQuery of some form. There are lots of clock scripts.
Related
I'm currently working on a browser game with a PHP backend that needs to perform certain checks at specific, changing points in the future. Cron jobs don't really cut it for me as I need precision at the level of seconds. Here's some background information:
The game is multiplayer and turn-based
On creation of a game room the game creator can specify the maximum amount of time taken per action (30 seconds - 24 hours)
Once a player performs an action, they should only have the specified amount of time to perform the next, or the turn goes to the player next in line.
For obvious reasons I can't just keep track of time through Javascript, as this would be far too easy to manipulate. I also can't schedule a cron job every minute as it may be up to 30 seconds late.
What would be the most efficient way to tackle this problem? I can't imagine querying a database every second would be very server-friendly, but it is the direction I am currently leaning towards[1].
Any help or feedback would be much appreciated!
[1]:
A user makes a move
A PHP function is called that sets 'switchTurnTime' in the MySQL table's game row to 'TIMESTAMP'
A PHP script that is always running in the background queries the table for any games where the 'switchTurnTime' has passed, switches the turn and resets the time.
You can always use a queue or daemon. This only works if you have shell access to the server.
https://stackoverflow.com/a/858924/890975
Every time you need an action to occur at a specific time, add it to a queue with a delay. I've used beanstalkd with varying levels of success.
You have lots of options this way. Here's two examples with 6 second intervals:
Use a cron job every minute to add 10 jobs, each with a delay of 6 seconds
Write a simple PHP script that runs in the background (daemon) to adds an a new job to the queue every 6 seconds
I'm going with the following approach for now, since it seems to be the easiest to implement and test, as well as deploy on different kinds of servers/ hosting, while still acting reliably.
Set up a cron job to run a PHP script every minute.
Within that script, first do a query to find candidates that will have their endtime within this minute.
Start a while-loop, that runs until 59 seconds have passed.
Inside this loop, check the remianing time for each candidate.
If teh time limit has passed, do another query on that specific candidate to ensure the endtime hasn't changed.
If it has, re-add it to the candidates queue as nescessary. If not, act accordingly (in my case: switch the turn to the next player).
Hope this will help somebody in the future, cheers!
I've search on the web and apparently there is no way to launch a php script without user interaction.
Few advisors recommend me Cron but I am not sure this is the right way to go.
I am building a website where auctions are possible just like ebay. And after an amount of time the objects are not available anymore and the auction is considered as finished.
I would like to know a way to interact with the database automatically.
When do you need to know if an object is available? -> Only if someone asks.
And then you have the user interaction you are searching for.
It's something different if you want to, let's say, send an email to the winner of an auction. In this case you'd need some timer set to the ending time of the auction. The easiest way to do this would be a cron job...
There are several ways to do this. Cron is a valid one of them and the one I would recommend if its available.
Another is to check before handling each request related to an object whether it is still valid. If it is not, you can delete it from the database on-the-fly (or do whatever you need to) and display a different page.
Also you could store the time at which your time-based script was run last in the database and compare that time with the current time. If the delay is large enough, you can run your time based code. However, this is prone to race conditions if multiple users hit the page at the same time, so the script may run multiple times (maybe this can be avoided using locks or anything though).
To edit cronjobs from the shell: crontab -e
A job to run every 10 minutes: */10 * * * * curl "http://example.com/finished.php"
TheGeekStuff.com cron Examples
Use heartbeat/bot implement
ation
Cron job that runs pretty frequently or a program that starts on boot and runs continuously (maybe sleeping periodically) is the way to go. With a cron job you'll need to make sure that you don't have two running at any given time or write it such that it doesn't matter if you have more than one working at any given time. With "resident" program you'll need to figure out how to handle the case when it crashes unexpectedly.
I wouldn't rely on this mechanism to actually close the auction, though. That should be handled in your database/web site. That is, the auction has a close time and either the database constraints or your code makes it impossible to bid on a closed auction. Notifying the winner and seller, setting up the payment process, etc. are things your service/scheduled task could do.
I'm aware of cron jobs to execute commands at a certain time, but what if that time is not constant? For instance, suppose a user asks for a reminder email exactly 1hr after signing up for something, is there an easy way to go about doing this?
Timing is critical. I am actually trying to create AI that will essentially act on its own but only at variable points during the day. Any help would be appreciated!
You can use at to schedule jobs for specific times. cron is for repeating jobs, at is for one-shot/oddball interval ones. Both have a resolution of 1 minute, though, so you can't specify a start period with seconds granularity.
The command's available on both Unix/Linux and Windows.
Here a workable flow:
user Requests email in 1 hour
You insert into the a table action (action_id, time)
On the PHP server create a cron job to check the action in the action table every minute, then do the action that need to be done at that time
That is a simple example from the request. It might get a bit more complex then that.
EDIT : this suggestion might be good only if you need to be very precise with the time management!
if you dont wanna use the cron triggers and you are not comfortable with them here are two php scheduling libraries..
1) http://www.php.brickhost.com/
2) http://www.phpjobscheduler.co.uk/
Try them if you like:
I have a few ideas about this but here is what I need to do and just wanted some second opinions really.
I am writing a small auction site in PHP/SQL, but I have come up against a hurdle.
When an item finishes, much like eBay, I need to be able to tell that it's finished and send out the emails to who has won it and who has sold it.
The only way I can think of is to schedule a piece of code to keep checking what auctions have ended but surely there is a better way?
The solution can be in multiple parts :
A script that is launched via Cron (every 5 minutes could be good, even less...). It detects the finished auction and put them in a queue.
A script, that pretty much runs continuously, and that processes items in the queue.
Note that :
You have to ensure that an auction is still open before displaying the page ! (a simple test) That way people can't join in after it closes.
For each script, you can use PHP, or any other language
Advantages :
The cron job is very fast, low on resources, and if there are a lot of auction to process, there is no risk it will be run in parallel (and then conflicts)
The queue system ensure that your system won't crash because there is too much going on... It will process the queue as fast as possible, but if it is not fast enough, the website will continue to run. You can however end up with emails being sent hours or days after the auction is closed. But the "limit" is way more predictible, and won't crash your system.
You can extend it in the future with multithreading processing of the queue, distributed processing... This is a scalable architecture.
This architecture is fun.
Additionnal informations :
Regarding the daemon script, I doesn't have to run continuously. What you can do is : at the end of the cron job, if there are items in the queue, then it checks if the other script (processing) is running. If yes then exit. If the other script is not running, it launches it...
The daemon script gets an item out of the queue and process it. At the end, if there are still items in the queue, it processes it, else, it exits.
With this system, everything is optimal and everyone loves each other !
To check if the other script is running, you can use a file and write in it "1" or "0" (= running / not running). The first script reads it, the second writes it... You can also use the database to do it. Or you can maybe use system tools or shell command...
Please be kind to share the SQL script that query the highest bidder based on the bidding end date (how to know the bidding is over) and award the product to the highest bidder
I would setup a cron job to run every 10-20-30-60 minutes etc to send out emails and update the auction details.
If you're script is fast, running it every minute or so may be alright.
Be aware that many shared hosting will only allow you to send out a certain number of emails per hour.
Do these emails need to be sent out instantly?,
I can see 2 possible problems and goals you are trying to achive:
Visual: You want that when a user browse your website, without updating or refreshing the page, it keeps updating the page so that if an audition ends, it appears something like "Audition ended, the item goes to...".
Solution: You should use Javascript and AJAX. (I assume you are already using it for countdowns or something). Make an AJAX call every 5 seconds (could be enough) and update the content.
Pratical: You want that if an audition is ended an user cannot join it. Solution: You can do it just with PHP and mysql. You could create a fields where you store the audition start timestamp and then make a simple if (time() >= ($timestamp + $duration)) {} (where $timestamp is the start of the audition and $duration is the duration of the audition) to block possible bad users trying to do it.
How can I set up a program in which a certain piece of data for a user is updated every hour. One example I can give is Mafia Wars. When you obtain property, your money is incremented every set amount of time based on which property it is. I'm not asking to spit out code for me, but rather to guide me in the right direction for a solution. I tried looking into cron jobs, but that only runs a script on a set time. Different users are going to be using this, and they may have different times to update their information. So thus, cron jobs are not applicable here.
You could still have cron jobs, just lots of them (not one per user, but maybe one per minute).
Also, Mafia Wars strikes me as not very interactive, so it may be enough to just update the data (after the fact) when the user (or some other part of the system) next looks at it. So when you log in after 37 hours, you get all the updates for the last 37 hours retroactively applied. Cheap trick, but if there is no need for a consistent global view, that might work, too.
A solution that I came up with when wondering how to implement such a thing is that whenever the player saves the game, the game saves the current time. Then, when the player loads the game back up, it calculates how many minutes have passed and figures out how much money the game should give the player. Then, you could update the SQL database to reflect the changes.
Why do you dismiss cron jobs? Have a cron job that runs a script in short intervals. Within this script, include logic to check which specific updates on the database have to be done.
A cron job that runs something is your friend.
What that something is, is up to you. It could be a PHP script that runs some mysql queries or procedures, or it could straight mysql command from the command line.
Either way, Cron (and other similiar tools) are exactly the bill for these tasks. It's lightweight, on nearly every server in the land, lots of help avaliable for it, and it 99.9999% of the time, it just works!