I'm trying to short poll an external API which doesn't support websockets, so I need to constantly make API requests every few seconds or maybe multiple times per second.
I also need to be in control of calling the next poll run. For example I wouldn’t want to run the poll again while my request is pending or I might want to increase the timeout if I get a 500 error.
Currently, considering doing this in a separate node process and only notify the rails server when there's new data. But I'd rather just do everything in the rails codebase.
I don't think ActiveJobs is built for this purpose but I could be wrong. I think what I really need is a separate entry point in the rails app repository that loads all the models but doesn't start the server and then write the loop for short polling, But not sure if that's best practice or trivial to do with rails.
So should I proceed with the node approach or is there an easy Rails solution I'm missing? Any suggestion or guidance is appreciated.
Maybe you can try whenever.
It help you run a method or a rake task with crontab.
# schedule.rb
every 1.minute do
runner "YourClass.your_method"
end
every 1.minute do
rake "polling:task"
end
After finish schedule.rb file, you'll need to execute whenever --update-crontab in you deploy pipiline in order to update crontab.
Related
Hi I making a petition site. In my site i Have three types of petitions, every have self period. When period is passed it need to change petition status(integer value) automaticaly.
How to do this better? And wich time rails use on server, from my pc or from server?
I ask about because I need somehow to test it manually.
I'm noviece, so if it's possible help me with simpliest alghoritm. I don't need a pure safety and performance.
I would suggest implementing it as a rake task, that will run every day as a cron job and update the mentioned value if record matches the condition(exactly one year passed).
Using this way you avoid problems related to performance as the rake task launches in separate background and also you may run the task when your server isn't overloaded by other tasks, for example at night.
Following gem is useful to setup jobs by schedule https://github.com/javan/whenever
Say I have an application that needs to pull data from an API, but that there is a limit to how often I can send a query (i.e., caps at X requests / minute). In order to ensure I don't hit this limit, I want to add requests to a queue, and have a background job that will pull X requests and execute it every minute. I'm not sure what's the best method for this in Rails, however. From what I gather, DelayedJob is the better library for my needs, but I don't see any support for only running X jobs a minute. Does anyone know if there is a preferred way of implementing functionality like this?
I'm a little late but I would like to warn against using the whenever gem in your situation:
Since you're using Ruby on Rails, using the whenever gem will be loading the environment each time it gets called in cron.
Give rufus-scheduler a try.
Place the code below, for example, in config/initializers/cron_stuff.rb
require 'rufus/scheduler'
scheduler = Rufus::Scheduler.start_new
scheduler.every '20m' do
puts 'hello'
end
First, I would recommend using Sidekiq for processing background jobs. It's well supported and very simple to use. If you do use Sidekiq, then there is another gem, called Sidetiq, that will allow you to run recurring jobs.
Maybe you can try [whenever]: https://github.com/javan/whenever
Then you can add your tasks as bellow:
every 3.hours do
runner "MyModel.some_process"
rake "my:rake:task"
command "/usr/bin/my_great_command"
end
in a schedule.rb file
I have a ruby on rails app in which I'm trying to find a way to run some code every few seconds.
I've found lots of info and ideas using cron, or cron-like implementations, but these are only accurate down to the minute, and/or require external tools. I want to kick the task off every 15 seconds or so, and I want it to be entirely self contained within the application (if the app stops, the tasks stop, and no external setup).
This is being used for background generation of cache data. Every few seconds, the task will assemble some data, and then store it in a cache which gets used by all the client requests. The task is pretty slow, so it needs to run in the background and not block client requests.
I'm fairly new to ruby, but have a strong perl background, and the way I'd solve this there would be to create an interval timer & handler which forks, runs the code, and then exits when done.
It might be even nicer to just simulate a client request and have the rails controller fork itself. This way I could kick off the task by hitting the URI for it (though since the task will be running every few seconds, I doubt I'll ever need to, but might have future use). Though it would be trivial to just have the controller call whatever method is being called by the periodic task scheduler (once I have one).
I'd suggest the whenever gem https://github.com/javan/whenever
It allows you to specify a schedule like:
every 15.minutes do
MyClass.do_stuff
end
There's no scheduling cron jobs or monkeying with external services.
Generally speaking, there's no built in way that I know of to create a periodic task within the application. Rails is built on Rack and it expects to receive http requests, do something, and then return. So you just have to manage the periodic task externally yourself.
I think given the frequency that you need to run the task, a decent solution could be just to write yourself a simple rake task that loops forever, and to kick it off at the same time that you start your application, using something like Foreman. Foreman is often used like this to manage starting up/shutting down background workers along with their apps. On production, you may want to use something else to manage the processes, like Monit.
You can either write you own method, something like
class MyWorker
def self.work
#do you work
sleep 15
end
end
run it with rails runner MyWorker.work
There will be a separate process running in the background
Or you can use something like Resque, but that's a different approach. It works like that: something adds a task to the queue, meanwhile a worker is fetching whatever job it is in the queue, and tries to finish it.
So that depends on your own need.
I know it is an old question. But maybe for someone this answer could be helpful. There is a gem called crono.
Crono is a time-based background job scheduler daemon (just like Cron) for Ruby on Rails.
Crono is pure Ruby. It doesn't use Unix Cron and other platform-dependent things. So you can use it on all platforms supported by Ruby. It persists job states to your database using Active Record. You have full control of jobs performing process. It's Ruby, so you can understand and modify it to fit your needs.
The awesome thing with crono is that its code is self explained. In order to do a task periodically you can just do:
Crono.perform(YourJob).every 2.days
Maybe you can also do:
Crono.perform(YourJob).every 30.seconds
Anyway you really can do a lot of things. Another example could be:
Crono.perform(TestJob).every 1.week, on: :monday, at: "15:30"
I suggest this gem instead of whenever because whenever uses Unix Cron table which not always is available.
Throwing out a solution just because it looks somewhat elegant and answers the question without any extra gems. In my scenario I wanted to run some code, but only after all my Sidekiq workers were done doing their thing.
First I defined a method to check if any workers were working...
def workers_working?
workers = Sidekiq::Workers.new.map do |_process_id, _thread_id, work|
work
end
workers.size > 0
end
Then we just call the method with a loop which sleeps between calls.
sleep 5 while workers_working?
Use something like delayed job, and requeue it every so often?
Use thin or other server which uses eventmachine, then just use timers that are part of eventmachine. Example: in config/application.rb
EM.add_periodic_timer(2) do
do_this_every_2_sec
end
With a Rails stack, how can I create a background process that handles events by spawning threads that are worked in real time?
The workers on Heroku pick up jobs every 5 seconds. I need real time. Ideally I'd like to get this working on Heroku, but if I need to, I will move away from it.
This has a long list of background workers: Background Job Manager for Rails 3 but it is not clear if your question heroku specific or not
I think you are looking for something like "run_later" which instead of queueing a job actually returns the request and runs a block in a separate process.
Here is a link to the Rails 3+ version, you can follow the fork network to find many other implementations:
https://github.com/Zelnox/run_later
(I don't use Heroku so I don't know if it runs on it)
Heroku runs rake jobs:work, so you can replace that with your own rake task, either running delayed_job with a shorter than 5 second timeout, or just performing your own task. Probably a good idea to keep a sleep statement in there.
The new cedar stack will run anything you want, so it might be worth checking that out.
With regards to run_later, or spawning from the current request, this does work but if the background process doesn't complete within the 30 second request timeout then heroku will kill it.
I think you need delay_job. please checkout this gem
If I need to create recurring tasks in delayed jobs, what is a clean solution? I have an import task that I want to run every 5 minutes, but I don't want to fire up rails/rake in order to tell it to create a Delayed job that can be picked up. If Rails is already running on a system, perhaps I can just create an HTTP request that will make the rails app fire off a DJ? I could put that cron task in a ruby script which runs every 5 minutes, making requests to a server, but without firing up rails. What do you think?
This fork of delayed_job has recurrence built right in (and there may be other forks that do the same):
http://github.com/andrewroth/delayed_job
The cron approach still seems to be quite clean. It need only involve running a rake invocation, not a full Rails server. Rake doesn't need Rails to be running to work.
However if you really don't like that approach then you could arrange for the recurring jobs to be re-queue themselves when they are being processed setting a run_at time to 5 minutes (or whatever) in the future. Obviously you'd need to prime the queue the first time and make sure the delayed_job server stays running
About that... I have the same desire,
I'm planning to have a cron to fire up a curl request at a specific route at my site every 5 minutes, so it runs a action with the result, and I'm gonna be pretty sure it only ran once.
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