Delayed methods

rubyonrails-talk
1

Hi, I faced such issue - my app should run some delayed method.

For example, I have Test model, which User can create. But to other users it should be visible only if it has :saved value in status attribute, which is assigned with special button.

I want to delete all tests, which remained unpublished 24 hours after creating.

And really don’t know where to start. Found Rails episode ‘Delayed Jobs’, but it is not what I’m looking for, it is mostly about background methods.

Can you give me any keys to topic, from where I can begin digging by myself?

2

You could write a rake task to do the work and then run that from cron daily or hourly or whatever is appropriate.

Colin

3

for regularly scheduled jobs, I use a mixture of cron (to create a delayed job), and the delayed_job itself

the crontab instance is very light, just a small (non-rails) rb script to insert the delayed_job in the delayed_jobs table

then the delayed_job instance will pickup the job and run it

in your instance, I would create a class method on the Test model - something like

def self.remove_old_unpublished

delete_all([“created_at < ? and state in(‘unpublished’)”, 24.hours.ago])

end

cron entry like this: 05 1 * * * cd /path/to/current && RAILS_ENV=production /path/to/current/lib/delayed_job_cron_jobs/create_delayed_job.rb --model “Test” --method “remove_old_unpublished” --queue “general” --arguments “{:any_argument => 42}”

4

I am always suspicious of the idea of doing something in a more complex way in order to save resources. It is only worth spending the additional time developing the solution if computing resources are likely to be an issue. Computing resources are usually cheaper than human resources.

Colin

5

that is a good thinking, just like normalization - then comes a time to denormalize

we have millions of visitors per month - and about 50 asynch processes - having one rails process deal with all those asynchs rather than one per is not helpful in any way

using a best practice such as my approach is not harder to implement and will scale - choosing an approach of equal complexity that won’t scale doesn’t hold water

6

Please bottom post (appending). It makes responses easier to find.

7

I’m just about to scale to a second app server - so good timing

in which ways did you find cron to be a poor choice ? on a single server they meet our needs nicely

you’d only run one clock instance per cluster - so much like cron (ie. no interserver clock scheduling). Have you tried using clock driven from a schedule described in the db (like a centralized cron, useful for failover) ?

Any thoughts you have on this topic appreciated

As for the OP, I hope they can see the short and long term options before them.

J

8

The primary issue when you bring in multiple servers is synchronization of the workers. Cron can't do that, as it only knows about one server. Having something that workers can distribute over requires something more sophisticated. That's what DJ is really about. Using clockwork makes it all the easier coming from cron.

9

Since all the OP is trying to do (I believe) is run a task occasionally to purge obsolete data from the database are those issues actually a problem?

Colin

10

yes - I know - I use DJ presently

my question was about what advantages you see with clockwork over cron - other than syntax I don’t see any advantages

now if the schedule was stored in the db, and I could run multiple clockworks on each server there would some inherent scheduling failover (DJ already provides job/worker failover)

11

Since the person I was answering directly asked about scaling to multipler servers, I'd say yes.

12

> I'm just about to scale to a second app server - so good timing > > in which ways did you find cron to be a poor choice ? on a single server > they meet our needs nicely > > you'd only run one clock instance per cluster - so much like cron (ie. > no > interserver clock scheduling). Have you tried using clock driven from a > schedule described in the db (like a centralized cron, useful for > failover) > ? > > Any thoughts you have on this topic appreciated > > As for the OP, I hope they can see the short and long term options > before > them. > > J > > > > >> >> Please bottom post (appending). It makes responses easier to find. >> >> > that is a good thinking, just like normalization - then comes a time >> > to >> > denormalize >> > >> > we have millions of visitors per month - and about 50 asynch >> > processes - >> > having one rails process deal with all those asynchs rather than one >> > per >> > is >> > not helpful in any way >> > >> > using a best practice such as my approach is not harder to implement >> > and >> > will scale - choosing an approach of equal complexity that won't >> > scale >> > doesn't hold water >> > >> > >> >> >> >> > for regularly scheduled jobs, I use a mixture of cron (to create a >> >> > delayed >> >> > job), and the delayed_job itself >> >> > >> >> > the crontab instance is very light, just a small (non-rails) rb >> >> > script >> >> > to >> >> > insert the delayed_job in the delayed_jobs table >> >> > >> >> > then the delayed_job instance will pickup the job and run it >> >> > >> >> > in your instance, I would create a class method on the Test model >> >> > - >> >> > something like >> >> > >> >> > def self.remove_old_unpublished >> >> > delete_all(["created_at < ? and state in('unpublished')", >> >> > 24.hours.ago]) >> >> > end >> >> > >> >> > cron entry like this: >> >> > 05 1 * * * cd /path/to/current && RAILS_ENV=production >> >> > /path/to/current/lib/delayed_job_cron_jobs/create_delayed_job.rb >> >> > --model >> >> > "Test" --method "remove_old_unpublished" --queue "general" >> >> > --arguments >> >> > "{:any_argument => 42}" >> >> > >> >> > the following gist is a script to insert delayed_jobs from cron >> >> > # create delayed_job entries without rails # # based on this http://aaronvb.com/articles/28-recurring-delayed-job-with-cron # enhanced to # take a params hash # read database.yml # delayed_job queue # use: # */30 * * * cd /path/to/current && RAILS_ENV=production /path/to/current/lib/delayed_job_cron_jobs/create_delayed_job.rb --model "MadmimiManager" --method "unsubscribed_update" --queue "general" --arguments "{:days_ago => 7}" · GitHub >> >> > >> >> > fyi, the reason to take this route over the simpler rake route >> >> > (run >> >> > rake >> >> > task from cron) is performance and memory usage - this method will >> >> > save >> >> > you >> >> > a bunch of both. >> >> >> >> I am always suspicious of the idea of doing something in a more >> >> complex way in order to save resources. It is only worth spending >> >> the >> >> additional time developing the solution if computing resources are >> >> likely to be an issue. Computing resources are usually cheaper than >> >> human resources. >> >> >> >> Colin >> >> >> >> -- >> >> You received this message because you are subscribed to the Google >> >> Groups >> >> "Ruby on Rails: Talk" group. >> >> To unsubscribe from this group and stop receiving emails from it, >> >> send >> >> an >> >> email to rubyonrails-talk+unsubscribe@googlegroups.com. >> >> To post to this group, send email to >> >> rubyonrails-talk@googlegroups.com. >> >> For more options, visit https://groups.google.com/groups/opt_out. >> >> >> >> >> > >> > -- >> > You received this message because you are subscribed to the Google >> > Groups >> > "Ruby on Rails: Talk" group. >> > To unsubscribe from this group and stop receiving emails from it, >> > send >> > an >> > email to rubyonrails-talk+unsubscribe@googlegroups.com. >> > To post to this group, send email to >> > rubyonrails-talk@googlegroups.com. >> > For more options, visit https://groups.google.com/groups/opt_out. >> > >> > >> >> If you're working in a distributed, multi-server and multi-process >> environment, cron is a poor solution. DelayedJobs and several others >> work in a distributed environment much better. I have been using the >> gem clockwork in addition to DJ, which makes things very simple. >> >> -- >> You received this message because you are subscribed to the Google >> Groups >> "Ruby on Rails: Talk" group. >> To unsubscribe from this group and stop receiving emails from it, send >> an >> email to rubyonrails-talk+unsubscribe@googlegroups.com. >> To post to this group, send email to rubyonrails-talk@googlegroups.com. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> > > -- > You received this message because you are subscribed to the Google > Groups > "Ruby on Rails: Talk" group. > To unsubscribe from this group and stop receiving emails from it, send > an > email to rubyonrails-talk+unsubscribe@googlegroups.com. > To post to this group, send email to rubyonrails-talk@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > >

The primary issue when you bring in multiple servers is synchronization of the workers. Cron can't do that, as it only knows about one server. Having something that workers can distribute over requires something more sophisticated. That's what DJ is really about. Using clockwork makes it all the easier coming from cron.

-- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-talk+unsubscribe@googlegroups.com. To post to this group, send email to rubyonrails-talk@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.

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This is a bottom post. Please follow suit.

yes - I know - I use DJ presently

my question was about what advantages you see with clockwork over cron - other than syntax I don't see any advantages

The advantage is that you'd need to be running cron on each of your servers managing workers, whereas clockwork only needs to run on one to keep things synchronized.

now if the schedule was stored in the db, and I could run multiple clockworks on each server there would some inherent scheduling failover (DJ already provides job/worker failover)

If you do decide to go that route, DJ can handle the requeuing itself, not needing anything else. It's just a bit more configuration and such.

13

As much as I've seen you ask people not to top post, I'm going to remind you to trim your emails, nobody wants to read 10 miles worth of quotes when you could simply trim it, like I did...

14

I understand that it is relevant to Jodi's problem, I was enquiring whether it is also relevant in the case described by the OP.

Colin