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Rails deployment missing piece, filled in (github.com)
41 points by koops on Feb 26, 2009 | hide | past | web | favorite | 27 comments

Why not just use cron for this? Yes, the syntax for this does look a lot cleaner, but cron really isn't that hard to use. Why add another layer of complexity (which may break and be difficult to debug) when you could simply add lines to a crontab?


Wow. I like Ruby but many in the community's obsession with reinventing the wheel (with slightly more syntactic sugar and a hip github page) is pretty difficult for me to understand.

Because if you have more than one machine running your app, you've got to reinstall the crontab everywhere. This keeps it DRY.

It also means that your crontab just went in source control, which is a detail a lot of people (i.e. me) forget.

Why not just keep the crontab file in your repo? A rake task that does `cp #{project_dir}/crontab /etc/crontab` would be sufficient to meet the same needs.

Whenever simply generates your crontab file for you using a cleaner syntax. It hasn't reinvented anything or added any complexity. You are just using cron.

But presumably you have to learn the new syntax?

Indeed, Ruby fans (I refuse to call them "Rubyists") love to talk about how Ruby is a great language for creating DSLs, which is true, but that doesn't mean you should create a new DSL for everything just because you can.

in this specific case, it's a bit more than 'just because you can'. Maybe it can be more like 'just because you don't want to have bugs popping around when you add new servers to your infrastructure because you forgot to setup a cronjob'

also, other languages usually offer the same kind of stuff - like Java EE's cron-like mechanisms, for instance (with or without DSLs)..

Very good addition to Rails, truly a missing piece as putting stuff in cronjobs spreads the logic of the app around. This makes it more readable as well.

Right--whatever your session cleanup strategy is, it's got to be run from cron.

It's great that the author includes a cap task in the documentation, though the role should usually be db, not app.

I'm the author -- thanks. To keep things very clean, we created a :cron role for our deployment (which happens to be the same server as our :db). I imagine that many people are running on one server and so the :app role is fine. The point is that you can deploy different cron schedules to your various server types using roles.

> whatever your session cleanup strategy is

... not really. If you're using cookie-store (the Rails default) or mem-cache-store (the fast, scalable option) there isn't any need for a session cleanup strategy.

I can definitely agree with the point on documentation - killer docs with real-life scenario examples are really key in adoption for stuff like this.

Storing sessions in a cache is a really bad idea. Too many sessions, and they start expiring randomly. I have been bitten by this, so I always store sessions in a non-lossy data store now. (BerekelyDB, FWIW.)

(As for in-cookie sessions, I like the idea, but it does require some server-side state to allow a user to invalidate his previous sessions. If someone steals the cookie, they have access to the system "forever", and the user has no recourse. The solution is to store a serial number in the user object, and reject sessions less than the current number, but I don't think Rails implements it this way by default.)

I am also not a big fan of running the cleanup job from cron. My main application has an event loop capable of firing timers (libev), so I use that to kick off a (forked) cleaning process. That requires no additional configuration on the system that the app is running on, which is just the way I like it. (Yeah, I know I am reinventing UNIX. UNIX needs to be reinvented.)

The event loop has other advantages, like non-blocking IO, and non-blocking subprocess invocations. A request can literally wait all day for a database query, and it won't prevent the app process from handling other requests.

> storing sessions in cache is a really bad idea

I've never had this issue, so I'm either using a bigger cache than you, or I'm storing less in the session.

>. Cookie store

I can't really speak to why the rails core team made this default, I think it's a step backwards.

> libevet...

That's certainly an option too. The beauty of this tool though isn't in the ruby syntax for cron. It's in using capistrano deployment flexibility and expressiveness for managing distributed crontabs.

I can't really speak to why the rails core team made this default, I think it's a step backwards.

"It's cool." Seriously though, they probably picked it because it requires no configuration. It also avoids hitting the database for things like "Logged in as jrockway", which is always a good thing.

Rails doesn't have any user management functionality. Most of the user libs do something to this effect with auth tokens.

Lol, I wrote "RailsCron" in 2005-2006. Funny to see how the ruby community iterates.

Cool. I'm in support of any syntax front-end that brings us closer to a future where everyone uses s-expressions for everything. ;P

(it's not s-expressions, but it's a step in the right direction)

nice, but is it possible to use it somewhere else than Rails, like say, Merb or Sinatra?

Not without a little hacking. After a little digging, it looks like it has an implicit Rails dependency (http://github.com/javan/whenever/blob/f036675e94cd9dd9b21d2c...)

It will work FINE without Rails. The code you're pointing to simply finds the Rails root if it exists as a convenience. If one doesn't, you have to manually tell Whenever your path: set :path, "/path/to/my/app"

I wrote something very similar to this a little while ago that's framework agnostic, http://www.github.com/jcapote/theman

cool, i didnt know about http://rufus.rubyforge.org/rufus-scheduler/ , that you're using in this project.

just bite the bullet and learn to use crontab ffs.

nice sugar though...

Nice, but does it work on Windows?

Do cron jobs work on Windows?

No, they don't. My question asked whether yours was a convenient wrapper for cron jobs or if you implemented the same functionality in a cross-platform manner. Thanks for your answer.

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