I'm using Phalcon 3.4 with PHP 7.2 and MySQL 4.7.3.
So in my Database I store dates (start_date and end_date) and I need to do something (send a mail to a customer) 48 hours before the start_date. I need to do that just once.
I think the only way to do that is to use cron job ?
I see only one solution for that . My solution is to create a cron job who call my web service every hour and inside my web service I gonna check if there is 1 or more start_date < to 48 hours compared from now. Then I get all related customers and I send an email for each customer.
I'm posting a question here because I'm not sure if it's very good to create an hourly cron job for that. I'd like to know if you know other solutions to do that. Maybe there is another technology ?
That's a perfect fit for cron indeed.
Possible pitfalls:
if the task takes longer than the interval (i.e. runs over 1 hr in your case), cron will happily run another one; if the processing gets long, you might want to check for that
cron won't run a missed task (e.g. if your task is scheduled at 2:30 and a DST change happens, it will skip and only run the next one) - that is already handled in your case by the "less than" check.
you may wish to set some sort of flag "this is currently processed" and then "this was processed successfully", so that e.g. a manual invocation doesn't process the same task while a cron is running
cron doesn't check that the task finished successfully, you may wish to check this directly in your main code, or run another "cleanup" cron service periodically
note also the timezones, where applicable (e.g. if all your date operations run in UTC, this is mostly a non-issue)
Related
I came across a situation i want to trigger some code at specific time, i.e when user does booking, the freelancer must accept/reject the booking request, if he doesnt, after x duration (15* mins lets say) it would be rejected and user would get push notification. All code is done but currently im running a cronjob after each 1 minute which checks for any unresponded bookings and checks when their time (15mins, dynamic) passed so then I execute my code for afterward, it is not good i guess as its running db queuries over and over each minute.
I'm aware with laravel queue jobs as well but didnt see anything for me to run that job for a specific time only (i.e execute this job after 15mins, if it isnt responded, reject it)
have you looked at Queue delay?
https://laravel.com/docs/9.x/queues#delayed-dispatching
This sounds like what you are looking for, I would just trigger the queue and delay when they make a booking so it executes 15 minutes after.
Use scheduled tasks.
use App\Console\Commands\SendEmailsCommand;
$schedule->command('emails:send Taylor --force')->daily();
$schedule->command(SendEmailsCommand::class, ['Taylor', '--force'])->daily();
https://laravel.com/docs/9.x/scheduling#scheduling-artisan-commands
On the surface it looks very simple problem that I am facing. In an enterprise web app (LAMP stack) we need to add some time based & schedule based tasks. Some examples are
when a user logs in and has stayed active for more than 30 minutes, send them a lucky coupon.
send a newsletter to subscribers every Monday. [easily handled by a cron job]
If a user does not login for 3 days, start stalking her. [doable by cron job but ...]
deduct phone bill amount from user account on 1st working day of every month at 9.
repeat failed deduction every subsequent work day at 9 for a max of 15 retries.
I hope that give you an idea of what is going on that needs to be handled.
At the moment we have cron jobs of almost every possible situation and they are kind of working but as you can see with the above scenarios, we are forced to run those crons almost every second (bit exaggeration but almost).
To handle the issue more elegantly and better implement the ddd concepts, we are thinking to make clock ticking as first class citizen of the application.
We would like to make a simple central clock ticker class, that will emit ticks as time events every second.
The ticks will be published to the central event bus.
And all the classes that are interested to act on the tick, will subscribe to the event bus.
What I am unable to figure out yet is that this will result in making a lot of subscriber/registrant classes code to run on every tick. As this is already the case with cron, could there be a better way to handle the subscription part so that a specific subscription is notified only when it needs to be notified?
And before we even get into solving this problem the way I am proposing, is there is a better way to handle this kind of problems? The key point in this whole scenario seems to be how to trigger something X based on how much time has passed since something Y happened in the domain. I believe I am not the first one to face this issue and this problem must have been long solved already but I am unable to stumble upon any road sign pointing me to the right direction.
The way I have handled this in the past is to queue commands as soon as I know something should happen and then the scheduler will fire off the commands when the time has come.
The scheduler is simply a process that runs as a service and wakes every N milliseconds to find any commands that have passed their ScheduledTime.
For example:
The user has logged in. Queue a command for 30 minutes hence to give them a coupon. After 30 minutes, the scheduler will send the command. If the session is still active, then the command is accepted and a coupon is presented. Otherwise, it simply does nothing.
You also mention several examples that are best handled by a traditional scheduler (cron as you mentioned) and will fire off a batch command. Depending on how knowledgeable your domain is about things like newsletters, you would either issue individual commands to your domain objects or simply pull a report and run a job to send emails.
If you do handle these types of processes in your domain, then your domain should also queue the next command. A saga or process manager would be most suitable for this type of operation. E.g.
CreateNewsletter (This is the batch) -> NewsletterCreated
Accounts.Each(SendAccountNewsletter) -> AccountNewsletterSent
NewsletterCompleted (This is the batch) ->
Queue(command: CreateNewsletter, when: NextMondayAt9) (This is the next batch)
Hope that helps.
P.S. If you publish ticks on your bus, you will have a ton of noise to filter through.
I want to setup a system for a privileged user to create a new task to run from date/time X to date/time Y saved in MySQL or SQLite? The task will send out a request to remote server via SSH and when the end date/time is up another SSH request would be sent.
What I'm not sure about is how to actually trigger the event at the start time and howto trigger the other at the end time?
Should I be polling the server somehow every 1min (sounds like a performance hit) or setup jobs in Iron.io/Amazon SQS or something else?
I noticed Amazon SQS only allows messages to queue for up to 14 days, how would that work for events weeks or months in the future?
Im not looking for code, just the idea on how it should work.
Basically there are two solutions, but maybe a hybrid version suits your problem best...
Use a queue (build into Laravel) and set up delayed jobs in the queue to be fired later on. You already mention that this might not be the best solution when a task takes months/weeks.
Use a cron job. Downside with this is that you can check once every day but that could mean a delay of 23h59m or you can check every minute but that might give you performance issues (in most cases it kind of works, but definitely not perfect).
Combining 1 & 2 might be the best solution; check in de beginning of a day whether there are tasks going to end in the coming day. If so, schedule a job in the queue to end the task at the exact time at which it should end. This gives you scalability and the possibility to create tasks that end a year after they where created.
I have a website in PHP and users can schedule message to be sent. I can sent message with command similar to this one:
php sendMsg.php 249
where number is ID of the message
Many people suggested to use cron jobs, but since I don't want to run this in interval cron is no option(only once - for example after 3 hours).
My idea was as follows:
$seconds = $hours*60*60;
exec('sleep '.$seconds.'; php sendMsg.php 249');
But this wont work because it will block php for further executing. What is the simplest way to achieve this?
You said you don't want to use a cron job because you only want the message sent once, but this is mis-understanding the way that a cron job would be written for this kind of task
Consider a situation where you have many users creating many messages to be sent at various given points in time.
You don't want to have a PHP program sitting running on your server all that time for each of those messages; it would be wasteful of server resources, even if they were all just sleep()ing for the duration.
Instead, one would use a cron job to run a short-lived PHP program once every minute (or whatever interval suits you).
Your message creation program would not be written to acually send the message; instead it would insert it into a database, along with the time it needs to be sent.
Meanwhile, the cronjob PHP program would scan this database every minute to see if there are any messages that are due to send but have not yet been sent. It would then send those messages and mark them as 'sent' on the DB.
This is the standard way to write this kind of thing, so it's not surprising that people are recommending it to you.
Doing it this way means that you never have a program running on your system for longer than necessary. Both PHP programs do their job quickly and exit, meaning that no-one is kept waiting for them.
It also makes it much more robust. Imagine if your server had to be rebooted. If you had a bunch of PHP programs running for hours waiting for their moment to send their message, they'd all be lost. On the other hand, if they had saved their message to a DB, the cron job would find them and send them correctly once the server was restarted.
Put the schedule in a database. Run a cronjob every minute or so, check the database if a message should be sent within this minute, and send it.
Is there a reason you don't want to use a cron job? That would be the simplest and most efficient way of sending the messages.
I would think that a cronjob ist still the right way
Create a table where the to be send messages are stored, with a timestamp when to be send and a flag for isSend
Create a cronjob - start php skript every 1 minute , which sends the messages with timestamp < current time and isSend = false
Ignore suggestions of cron, if you want to simply wait a period of time then use the at scheduler:
$hours = 2;
$command = sprintf('echo "php sendMsg.php 249" | at now + %d hours', $hours);
exec($command);
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: