I need to implement user faced scheduler, like users have reports and might choose schedule when they want those reports being sent to them.
Requirements are quote complex, like there should be schedules like each 12 hours, each 30 minutes, each second day, at Fridays at 1am, last Sunday of the months etc.
Is there Rails solution for that our should I create it from the ground?
Thanks!
Most schedulers for rails and ruby depend on a static file. You can use a queuing system like Delayed Job and make every job enqueue itself for next time after success. Or you can do a basic SheduledJob model which relates to the user, and stores the periodicity, next execution and last execution. And use a normal (frequent) scheduled task engine like clockwork to check for pending jobs.
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I have an Ruby on Rails application which allows the user the execute certain jobs. These jobs are handled and executed by Sidekiq.
Now I want to give the user the possibility to schedule these jobs and like cron jobs allow them to be recurring on certain dates and time. The question is how to do this?
All Gems I have come across so far, like whenever, rufus, sidetiq or simple cron jobs only allow for the job to be hardcoded in a file. But what I want is a job that is set by the user and stored in the database.
The obvious way would be to create a cron that checks the database every minute for jobs that are due, executes them and sets the date and time to the next scheduled point. But this way also involved a lot of coding and seems to be a little complicated. Also I see it as a fake cron, because there is simply one cron job that always checks the database.
What I would really like is a solution where the user actually creates a cron job, but I didn't come across anything so far that does this. Also it doesn't have to be a Gem. A more simpler way of just doing this would be enough. And I'd like to think that I can't be the only one who wants to do something like this.
I'm creating flight booking website in Rails. Booking information is stored in database in the following table:
USERNAME | FLIGHT FROM | FLIGHT TO | DATE OF FLIGHT | TIME OF FLIGHT | some additional information not relevant to this task ... |
I'm looking to send an email an hour (or some specific time) before the TIME OF FLIGHT on a DATE OF FLIGHT. What is the best approach to do it ? I was looking into Cron and delayed_job however both seem to be based more on intervals rather than executing a job at specific date and time.
Please help.
Thank you
The simplest approach is just to have a cron job set to run every 10 minutes and determine via a database query which flights now require a reminder e-mail. You can have an additional field in the database such as "REMINDER_SENT" so that you only send an e-mail once.
If you are already using delayed job then the cron job should just call a ruby script which adds a SendReminders job on to the queue. You can then manage all of the db querying, e-mail sending and db updating from a normal delayed job.
This approach saves you having to queue up a large number of future dated events and you don't need to worry about flight times changing or events getting lost. If you miss one event then the next run in 10 minutes will pick up all the flights anyway.
Are you required to send those notifications exactly one hour (or another time) in advance?
If not I would create a cron job that calls a rake task, say every 10 minutes. This task checks if there are notifications due and sends them. If you expect them to arrive 60 minutes before, with these settings you have a delivery timeframe between 60-70 minutes in advance, given the delays imposed by spam filters etc I think this is reasonable.
If you call the script more often (every minute), the precision is higher, but you might have trouble with concurrently running tasks.
I know about Heroku Scheduler addon but is it very flexible like I want to be able run a task on the 1st and 15th of every month as well as at daily intervals.
What else can I use or is Scheduler the best option for Heroku?
According to my knowledge Scheduler is the best option. It is good and reliable go for it.
If you lowest frequency of running a task is it daily then config scheduler to run daily and then in the code that it runs check the day of the month and perform your desired tasks whether it be day 1, day 15 or day x.
If that doesn't suit then you'd need to look at one of the background processors like Sidekiq, DelayedJob etc that allowed scheduled jobs and then have your jobs requeue themselves at whatever frequency you want but you'll need to be running a worker for this to work in a similar fashion to scheduler.
I'd like to make an email notification if SomeModel has not been updated for 2 hours.
What is the best way to implement it?
After a model has been saved, queue up a background job to run 2 hours from that time to send the email. When a new job is enqueued, remove any still-unrun jobs that are still on the queue.
resque-scheduler providers a pretty simple way of doing this, assuming you have redis up and running.
Personally I find the solution that #x1a4 proposes to be somewhat overkill. Given the relatively large window of 2 hours, I would just run a job periodically (say, once every 10-15 minutes), then search all Models for updated_at <= 2.hours.ago and send out the emails.
As for scheduling that job to run every 15 minutes, there are several options. You may use resque-scheduler, if you are using Resque. You may also use the standard system cron, but will incur some fairly substantial overhead starting Rails each time the job runs. I also have written a distributed scheduler gem (i.e. cron that can run on multiple machines, but act like it's only running on one), which uses Redis under the hood.
Is there a way to setup a callback in ROR that would trigger at a specific time?
Lets say I'm running a contest that expries at a certain time. Lets say Monday July 28th at 9:00. I'd like to set up an observer that ran a function at Monday July 28th at 9:00. Does rails have a method to do this?
There's a run_at field in Delayed Job. You have to have a worker process in the background always running and looking for jobs that a set to run, but if your application is doing this a lot, it might be easier than always writing new cron jobs.
So, you could have a method in your Contest model that gets called in a after_create callback that sets up a delayed job to send out an email to a random winner at the date that's specified.
If it's a one time, or very infrequent deal, though, I'll agree about using whenever
You'd be better off writing a ruby script that runs via crontab at the exact time you need it to.
I agree about crontab, but I like whenever. It has a nice integration into cron that you can store with your repo and it integrates nicely with capistrano.