I'm integrating some non-rails-model tables in my Rails application. Everything works out very nicely, the way I set up the model is:
class Change < ActiveRecord::Base
establish_connection(ActiveRecord::Base.configurations["otherdb_#{RAILS_ENV}"])
set_table_name "change"
end
This way I can use the Change model for all existing records with find etc.
Now I'd like to run some sort of notification, when a record is added to the table. Since the model never gets created via Change.new and Change.save using ActiveRecord::Observer is not an option.
Is there any way I can get some of my Rails code to be executed, whenever a new record is added? I looked at delayed_job but can't quite get my head around, how to set that up. I imagine it evolves around a cron-job, that selects all rows that where created since the job last ran and then calls the respective Rails code for each row.
Update Currently looking at Javan's Whenever, looks like it can solve the 'run rails code from cron part'.
Yeah, you'll either want some sort of background task processor (Delayed::Job is one of the popular ones, or you can fake your own with the Daemon library or similar) or to setup a cronjob that runs on some sort of schedule. If you want to check frequently (every minute, say) I'd recommend the Delayed::Job route, if it's longer (every hour or so) a cron job will do it just fine.
Going the DJ route, you'd need to create a job that would check for new records, process them if there are any, then requeue the job, as each job is marked "completed" when it's finished.
-jon
This is what I finally did: Use Whenever, because it integrates nicely with Capistrano and showed me how to run Rails code from within cron. My missing peace was basically
script/runner -e production 'ChangeObserver.recentchanges'
which is now run every 5 minutes. The recentchanges reads the last looked-at ID from a tmp-file, pulls all new Change records which have a higher ID than that and runs the normal observer code for each record (and saves the highest looked-at ID to the tmp-file, of course).
As usual with monitoring state changes, there are two approaches : polling and notification. You seem to have chose to go the polling way for now (having a cron job look at the state of the database on a regular basis and execute some code if that changed)
You can do the same thing using one of the rails schedulers, there are a few out there (google will find them readily, they have various feature sets, I'll let you choose the one which suits your need if you got that way)
You could also try to go the notification way depending on your database. Some database support both triggers and external process execution or specific notification protocols.
In this case you are notified by the database itself that the table changed. there are many such options for various DBMS in Getting events from a database
Related
So I created a client-server (Rails for both client and server) system that will have many clients with one server, that interact using REST.
The clients can send / update / delete their own "Jobs" on the server, which is right now simply a table named Jobs. The Jobs belongs_to a table named Apps, which ofcourse has_many jobs (each App entry represents a client, so the client can only add / delete / update / read their jobs on the server).
The purpose of this, is so the client can add entries to the Jobs table and specify a Time of Day (in the future), that they can run a Job. The Job that gets run is a call to a 3rd party email-service to send an email.
So I need a Jobs framework, that can easily run on Heroku, and iterate through my Jobs table (say, every half-hour.. Or even every 5 minutes maybe..), and see if there are any Jobs it needs to run based on a datetime column (check if the datetime entry is equal-to, or less-than the current-time the Worker is running)
Which is the best Rails / Heroku Job framework I should use for this?
I prefer simplicity, so I was looking at:
https://devcenter.heroku.com/articles/scheduler
But, I cannot use this because it warns:
Scheduler is a “best effort” service, meaning that execution is expected but not guaranteed. Scheduler is known to occasionally (but rarely) miss the execution of scheduled jobs"
So next I looked at at https://devcenter.heroku.com/articles/scheduled-jobs-custom-clock-processes - which can be implemented using Gems like Resque or Delayed Job.. Which I am currently researching now..
Ideally, I wanted to be able to find a Job Framework that would compliment (or replace) my jobs table (So, Whenever I add something to my Jobs table or delete it, each of my Job entries would have a 1:1 relation with an actual Job in the Job framework, that I would also be adding / updating / deleting when I add / update / delete an entry on my Jobs table and / or the Jobs entry in the Job Framework). Ofcourse I would be writing the logic for all the CRUD operations on the server (once it receives a REST call from the client) - But the client needs to be able to delete and re-add all it's jobs on the server at any-moment; and I did not see any Job frameworks that would allow me to dynamically add and remove future jobs at any given time, dynamically. All the existing frameworks seem like they are created for scheduled jobs to run at specific times or time intervals, specified in a config file. Which is fine, but I wanted to check on S.O to verify that I am making the best decision when choosing my setup / framework
Sorry for the long / complex question - and I appreciate any suggestions or recommendations anyone has for me!
Thanks!!!
This sounds like a job for Resque and Resque-scheduler.
Here's a syntax example :
Resque.enqueue_in(5.days.from_now, SendFollowupEmail, argument)
If you need to delete it before it is executed :
Resque.remove_delayed(SendFollowUpEmail, :user_id => current_user.id)
Im on Rails 4, I'm creating a listing/rental site where people can list things and then other people can rent them. I'm using Stripe to handle all my payments, and I have a form set up that gets the users credit card and makes them a customer when they request to book a rental. After that, the owner of the rental can view the request and confirm or deny it. If they confirm it, the user renting gets their card charged and their money goes into holding.
When a user requests a booking, they choose a pick-up and drop-off date. I would like to have an action that calls a payout from stripe to the listings owner 24 hours after the pick up date. I am not sure how to go about this, so any suggestions are great! Of course if anyone knows of any tutorials implementing such a thing that would be awesome :).
Thanks.
Couple of things you can do
delayed_job: requires a database and a running process to run scheduled jobs; You can use it on heroku as shown here
resque-scheduler: requires redis and resque and a running process to run scheduled jobs. You can use it on heroku as shown here. Use resque-web and resque-cleaner to check and handle failed jobs.
whenever: requires access to cron jobs and your own script to be setup to run every hour or every few minutes to then pickup listings that need to be processed and then process them away. You'll need to work out a good error reporting system. Doesn't run on heroku
heroku scheduler: that is all managed through heroku but essentially gives you the same capabilities as whenever.
Resque would probably be my choice, but you should know better about your domain.
Install the whenever gem and documentation is available here: https://github.com/javan/whenever
Then in config/scheduler.rb file mention your function name and defined in the model or as per requirement. It will be behave like CRON job but major difference is that it can run application internal function as well.
There are many ways of doing this.
All of which involve some sort of data store that is checked every X minutes. Within this data store you can usually set a run on time.
Checkout:
https://github.com/collectiveidea/delayed_job
or
https://github.com/mperham/sidekiq
I have a page of a long list of items. Each has a check box next to it. There's a jQuery check-all function, but when I submit all of them at once, the request times out because it's doing a bunch of queries and inserting a bunch of records in the MySQL database for each item. If it were to not timeout, it'd probably take about 20 minutes. Instead, I just submit like 30 at a time.
I want to be able to just check all and submit and then just go on doing other work. My coworker (1) said I should just write a rake task. I did that, but I ended up duplicating code, and I prefer the user interface because what if I want to un-check a few? The rake task just submits them all.
Another coworker (2) recommended I use fork. He said that would spawn a new process that would run on the server but allow the server to respond before it's done. Then, since an item disappears after it's been submitted, I could just refresh the page to check if they're done.
I tried this on my local, however, it still seems that Rails is waiting for the process to finish before it responds to the POST request sent by the HTML form. The code I used looks like this:
def bulk_apply
pid = fork do
params[:ids].each do |id|
Item.find(id).apply # takes a LONG time, esp. x 100
end
end
Process.detach(pid) # reap child process automatically; don't leave running
flash[:notice] = "Applying... Please wait... Then, refresh page. Only submit once. PID: #{pid}"
redirect_to :back
end
Coworker 1 said that generally you don't want to fork Rails because fork creates a child process that is basically a copy of the Rails process. He said if you want to do it through the web GUI, use BackgroundJob (Bj) (because we're already using that in our Rails app). So, I'm looking into BackgroundJob now, but what do you recommend?
I've had good success using background job. If you need rails you will be using script/runner which still starts up a new process with rails. The good thing is that Backround Job will make sure that there is never more than one running at a time.
You can also use script runner directly, or even run a rake task in the background like so:
system " RAILS_ENV=#{RAILS_ENV} ruby #{RAILS_ROOT}/script/runner 'CompositeGrid.calculate_values(#{self.id})' & " unless RAILS_ENV == "test"
The ampersand tells it to start a new process. Be careful because you probably don't want a bunch of these running at the same time. I would definitely take advantage of background job if it is already available.
you should check out IronWorker . It would be super easy to do what you want and it doesn't matter how long it takes.
In your action you'd just instantiate a worker which has the code that's doing all your database queries. Example worker:
Item.find(id).apply # takes a LONG time, esp. x 100
And here's how you'd queue up those jobs to run in parallel:
client = IronWorkerNG::Client.new
ids.each do |id|
client.tasks.create("MyWorker", "id"=>id)
end
That's all you'd need to do and IronWorker takes care of the rest.
Try delayed_job gem. This is a database-based background job gem. We used it in an e-commerce website. For example, sending order confirmation email to the user is an ideal candidate for delayed job.
Additionally you can try multi-threading, which is supported by Ruby. This could make things run faster. Forking an entire process tends to be expensive due to memory usage.
I have a rails app deployed on Heroku. I want to add a feature that enables users of the app to set a reminder. I need some way for the app to schedule sending an email at the time specified by the user.
I have found numerous posts referring to using delayed_job for this, but none of the write-ups / tutorials / etc. that I have found directly address what I am trying to accomplish (the descriptions I have found seem more geared towards managing long-running jobs that are to be run "whenever").
Am I on the right track looking at delayed_job for this? If so, can somebody point me towards a tutorial that might help me?
If delayed_job is not quite right for the job, does anybody have a suggestion for how I might approach this?
The most typical way of handling this is to use a cron job. You schedule a job to run every 15 minutes or so and deliver any reminders that come up in that time. Unfortunately, heroku only allows cron jobs to run every hour, which usually isn't often enough.
In this case, I'd use delayedjob and trick it into setting up a recurring task that delivers the notifications as often as necessary. For example, you could create a function that begins by rescheduling itself to run in 10 minutes and then goes on to send any reminders that popped up in the previous 10 minutes.
To view delayedjobs send_at syntax to schedule future jobs check here: https://github.com/tobi/delayed_job/wiki
ADDED after comments:
To send the reminder, you would need to create a function that searches for pending reminders and sends them. For example, let's say you have a model called Reminder (rails 3 syntax cause I like it better):
def self.find_and_send_reminders
reminders = Reminder.where("send_at < ? AND sent = ?", Time.now, false).all
reminders.each do |r|
#the following delayed_job syntax is apparently new, and I haven't tried it. came from the collective_idea fork of delayed_job on github
Notifier.delay.deliver_reminder_email(r)
#I'm not checking to make sure that anything actually sent successfully here, just assuming they did. may want to address this better in your real app
r.update_attributes!(:sent => true)
end
#again using the new syntax, untested. heroku may require the old "send_at" and "send_later" syntax
Reminder.delay(:run_at => 15.minutes.from_now).find_and_send_reminders
end
This syntax assumes you decided to use the single reminder entry for every occurence method. If you decide to use a single entry for all recurring reminders, you could create a field like "last_sent" instead of a boolean for "sent" and use that. Keep in mind these are all just ideas, I haven't actually taken the time to implement anything like this yet so I probably haven't considered all the options/problems.
Check out the runt gem, may be useful for you: http://runt.rubyforge.org/
You can use delayed_job's run_at to schedule at a specific time instead of whenever.
If your application allows the users to change the time of the reminders you need to remember the delayed_job to be able to update it or delete it when required.
Here is more details.
It's good to avoid polling if you can. The worker thread will poll at the database level, you don't want to add polling on top of polling.
How would I go about sending an email to a user, say, 48 hours after they sign up, in Ruby on Rails? Thanks!
As Joseph Daigle mentioned, you need to obviously record the exact date and time the user registered. After that, you need a cron running every certain number of minutes (every hour, for example) checking to see if there's any new users whose registration time is greater than 48 hours, send a mail to said user and mark that user as already emailed, so you don't email them again.
As per the actual mail sending, check out the following documentation page:
http://wiki.rubyonrails.org/rails/pages/HowToSendEmailsWithActionMailer
It has all you need to know to send mails with RoR.
I recommend that you use the latest version of BackgrounDRb to handle this. You can read about BackgrounDRb here: http://backgroundrb.rubyforge.org/
In order to queue a message for later delivery, the BackgrounDRb client code (in your application model's after_create callback, maybe) could look something like this:
MiddleMan(:email_worker).enq_send_email_task(:message => #message,
:job_key => "notify1",
:scheduled_at => Time.now + 48.hours)
You'd have to build a BackgrounDRb worker to handle sending the email:
# RAILS_ROOT/lib/workers/email_worker.rb
class EmailWorker < BackgrounDRb::MetaWorker
set_worker_name :email_worker
def send_email_task(message)
# ... Code to send the email message
end
end
Note that in order to use BackgrounDRb in this way, you have to use persistent job queues, so make sure you run the migration included with BackgrounDRb to set up the persistence table in your application.
BackgrounDRb is started separately from Rails (mongrel, apache, etc) using 'script/backgroundrb start', so make sure that you add the daemon to whatever process monitoring you're using (god, monit, etc) or that you create an /etc/init.d script for it.
First you're going to need a running daemon or background service which can poll your queue (probably from in a database) every few minutes.
The algorithm is pretty simple. Record the time of the user event in the queue. When the daemon checks that item in the queue, and the time difference is greater than 48 hours, prepare the e-mail to send.
You can queue jobs with a delay using async observer. Ideally, anything you have that isn't known to be instant (or very close to it) all the time should pass through something like that.
I wrote a plugin called acts_as_scheduled that may help you out.
acts_as_scheduled allows you to manage
scheduled events for your models.
A good example of this is scheduling
the update of RSS Feeds in a
background process using Cron or
BackgroundRB.
With acts_as_scheduled your schedule
manager can simply call
"Model.find_next_scheduled()" to grab
the next item from the database.
How I would approach this is by creating a scheduling controller, that will query the database for the next_scheduled and then use a mailer to send the message. The you set up a Cron Job to call the controller periodically using WGET or CURL. The advantage of the Cron/Controller approach is that no further infrastructure or configuration is required on the server and you avoid complicated threading code.
I think I'd be inclined to store the need for the email and the earliest time after which it should be sent, somewhere separate, then have my things-to-do task look at that. That way I only have to process as many records as there are emails to be sent, rather than examine every user every time, which would either get tedious or require an otherwise probably unnecessary index. As a bonus, if I had other tasks to be performed on some sort of a diarised basis, the same construct would be useful with little modification.