In Oracle, we can create JOBs and configure them to run every 2 hours / every morning / etc. as per project requirement.
Does Yugabyte also support such JOBs - i.e. periodic automatic re-execution of stored-procedures?
Internal cron jobs aren't available by default in PostgreSQL & YugabyteDB.
You have to execute the cron job outside the database.
There is pg_cron extension for PostgreSQL though we haven't tested it with YugabyteDB.
Related
I'm new to Rails so I'm not sure if this is a stupid question but...
I have to run regular tasks to populate data to my Rails app. Today I use the whenever gem to create Cron entries to run these tasks on my system. I want to migrate my Rails app to Docker so that I can scale it more easily. I know that in Drupal(PHP) there is Poorman's Cron which uses requests to drive schedules.
Is there a way to implement scheduling inside Rails without using Cron or a better way of managing regular tasks that works well with Rails?
Yes, I created https://github.com/Ebbe/arask to keep stuff simple.
No need to install anything (other than the gem) or setup anything outside of rails. No background process, except for the actual job.
Add gem 'arask' to your Gemfile, run bundle install, rails generate arask:install and rails db:migrate.
Now you can setup your tasks in the file config/initializers/arask.rb:
arask.create script: 'puts "IM ALIVE!"', interval: :daily
arask.create task: 'my:awesome_task', interval: :hourly
arask.create task: 'my:other_awesome_task', interval: 2.hours
The tasks will automatically run if the server is running.
Is there a way to implement scheduling inside Rails without using Cron
or a better way of managing regular tasks that works well with Rails?
Cron is pretty much the go to tool for running scheduled activities on *nix system and most gems actually leverage cron under the hood, in fact avoiding cron is probably a lot more work unless you want to use a third party service.
One of the new features of Rails 5 is ActiveJob:
Active Job is a framework for declaring jobs and making them run on a
variety of queuing backends. These jobs can be everything from
regularly scheduled clean-ups, to billing charges, to mailings.
Anything that can be chopped up into small units of work and run in
parallel, really.
It can be used with several backends:
Sidekiq
Resque
Sucker Punch
Queue Classic
I have a backend Rails JSON API.
Every X amount of hours, there is some data I would like to purge.
So I need to be able to run some commands every X hours.
How can I accomplish this in Rails?
Whenever is a Ruby gem that provides a clear syntax for writing and deploying cron jobs.
It is an easy way to write cron jobs to a cron tab file which is later on executed by the system. It provides you a nice DSL to schedule your tasks.
Let's assume you have a test action in YourModel that you want to run every 24 hours, so you will be doing this:
your_model.rb
def test
# Do Something...
end
schedule.rb
every 24.hours do
runner 'YourModel.test'
end
You need to run the following command on your project to do create the crontab:
whenever -i
You can use this gem whenever (https://github.com/javan/whenever), which will help you manage scheduling using crontab.
I had developed an application that has delayed job and cron job and I need to deploy it to Heroku. I realized my delayed job need Heroku adds-on, "Heroku Scheduler Standard" and it costs $34.50.
1) Does that mean I need to buy that so that my delayed and cron job will run automatically?I wonder if delayed job and cron job can be done by using Heroku schedular then why we still need javan/whenever and collectiveidea/delayed_job? Can I use these in Heroku preferably in free condition?
2) My cron job does not worked in Heroku. How do I run my whenever gem in heroku?
There appear to be a couple of thoughts intermixed in your question. I'll do my best to separate them:
a) DelayedJob on Heroku
One way to process jobs queued in DelayedJob (i.e. records sitting in the delayed_jobs table in your database) is to run the following rake task:
$ rake jobs:work
On heroku, this rake task is commonly run via a 'worker' process.
By default for rails apps, your heroku app should already come with a slider for 'workers' (initially set to 0) that will run the rake task above. Merely sliding this to '1' (which will cost you around $34.00 per month) will launch the DelayedJob dequeue process in the background on a dedicated heroku instance, with your codebase, independent of your web dynos.
Note that DelayedJob does NOT require Heroku's "Scheduler" add-on.
Also note that heroku charges by hours of processing per month. So, if you slide your 'worker' to '1' for one hour a month, and then slide it back to '0' again when you're done, you will be paying far, far less than the ~$34 charge. There is a way to slide workers on and off programatically too.
b) Cron on Heroku
As it stands, managing your own, customized cron file is not possible on heroku or other cloud-based app service providers. Everything is ephemeral, and deployed files cannot be altered by you or your code.
Heroku's Scheduler is the appropriate add-on in this case to replace cron. You should be able to set tasks in your heroku scheduler to do what your cron tasks are currently doing.
Last I checked, heroku's scheduler was free (see: https://addons.heroku.com/scheduler), so I'm not sure why you state it is $34.50.
Hope this helps.
I am new to this and is little confused about how Delayed Job works ?
I know it creates a table and puts the jobs in the table and then I need to run
rake jobs:work
to start the background process. Now my question is
Does DJ script checks the table every minute and when the time matches job_at time, it runs that job ?
How it is different than cron (whenever gem) if the script is just checking the table every min ?
Thanks
Does DJ script checks the table every minute and when the time matches job_at time, it runs that job ?
When you run rake jobs:work DelayedJob will poll the delayed_jobs table, performing jobs matching the job_at column value if it's been set. This part you're correct about.
How it is different than cron (whenever gem) if the script is just checking the table every min ?
whenever is a gem that helps you configure a crontab. It has nothing directly to do with performing tasks on your server on a periodic basis.
You could setup a cron to run whatever tasks exist in the queue every minute, but leaving a delayed_job daemon running has multiple benefits.
Even if the cron ran every minute, delayed_job's daemon will see and perform any jobs queued within that 1-minute window between cron runs
Every time the cron would run, it will rebuild a new Rails environment in which to perform the jobs. This is a waste of time and resources when the daemon can just sit there immediately ready to perform a newly queued job.
If you want to configure delayed_job through a cron every minute you can add something like this to your crontab
* * * * * RAILS_ENV=production script/delayed_job start --exit-on-complete
Every minute, delayed_job will spin up, perform whatever jobs are ready for it or which it must retry from a previously failed run, and then quit. I don't recommend this though. Setting up a delayed_job as a daemon is the right way to go.
Does DJ script checks the table every minute and when the time matches
job_at time, it runs that job ?
yes. It checks the database every 5 seconds.
How it is different than cron (whenever gem) if the script is just
checking the table every min ?
In the context of background jobs, they are not that different. Their main difference is how they usually run the jobs.
DJ | Crontab
uses additional database | you should either set up a rake task
table but that's it. easier | or a runner which can be called on the
to code compared to crontab | crontab
------------------------------|------------------------------------------
requires you to run a worker | requires you to setup your cron which
that will poll the database | you can easily do using the whenever gem
------------------------------|------------------------------------------
since this uses a table, it | you have to setup some sort of logging so
is easier to debug errors | that you have an idea what caused the error
when they happen |
------------------------------|------------------------------------------
the worker should always be | as long as your crontab is set up properly,
running to perform the job | you should have no issues
------------------------------|------------------------------------------
harder to setup recurring | easy to setup recurring tasks
tasks |
------------------------------|------------------------------------------
I created an app that uses the whenever gem. The gem creates cron jobs. I got it working locally but can't seem to get it working on heroku cedar. What's the command to do this?
running:
heroku run whenever --update-crontab job1
doesn't work
Short answer: use the scheduler add-on: http://addons.heroku.com/scheduler
Long answer: When you do heroku run, we
spin up a dyno
put your code on it
execute your command, wait for it to finish
throw the dyno away
Any changes you made to crontab would be immediately thrown away. Everything is ephemeral, you cannot edit files on heroku, just push new code.
You need to add Heroku Scheduler addon.
You can add it directly from your dashboard or using following commands:
install the add-on:
heroku addons:create scheduler:standard
Create a rake task in lib/tasks
# lib/tasks/scheduler.rake
task :send_reminders => :environment do
User.send_reminders
end
Schedule job
Visit Heroku Dashboard
Open your app
Select Scheduler from add-ons list
Click Add Job, enter a task and select frequency.
e.g. Add rake send_reminders, select "Daily" and "00:00" to send reminders every day at midnight.
The other answers specify you should use the Heroku Scheduler add-on, and it is able to run a background tasks indeed, but it doesn't support the flexibility of cron.
There's another add-on, called Cron To Go, that is able to run your jobs on one-off dynos with cron's flexibility. You can also specify a timezone for your job and get notifications (email or webhook) when job fail, succeed or start.
(Full disclosure - I work for the company that created and operates Cron To Go)
If you want to:
Use Heroku Scheduler
Run tasks every minute (not 10 min)
Don't care about dyno hours
This was my solution hack to run jobs every minute - assuming the task completes in under 60 seconds.
task start_my_service: :environment do
1.upto(9) do |iteration|
start_time = DateTime.now
Services::MyService.call
end_time = DateTime.now
wait_time = 60 - ((end_time - start_time) * 24 * 60 * 60).to_i
sleep wait_time if wait_time > 0
end
end
Heroku doesn't support cron jobs. And there are two drawbacks to the Heroku Scheduler :
you cannot choose an arbitrary interval or time at which to run jobs (it's either every 10 mins, 1 hour or daily).
your jobs are not defined in code, hence not in your versioning system and not easy to keep track of or modify.
Heroku does provide an alternative : custom clock processes. But the clock process requires its own dyno, and "Since dynos are restarted at least once a day some logic will need to exist on startup of the clock process to ensure that a job interval wasn’t skipped during the dyno restart".
Simple scheduler is a gem made specifically made for scheduling on Heroku, but seems a bit hackish.
I ended up using sidekiq-cron. Only drawback : if sidekiq is down right when a job is scheduled to run, the job won't run.