[Rails] Re: Can I update session variable in a new thread?
>> But it is do-able, although not easy, I don't think you can get away >> with just trying to access the session array itself in a thread that's >> out of the request loop. Sorry, this is a topic of interest to me that noone else is ever interested in talking about. PPS: REALLY, if you decide you want to set off a thread that will persist after the response is returned, despite the general pain in the neck of doing that cause neither ActiveRecord nor MRI 1.8 Ruby are entirely happy with it (but it's still possible if you take the right precautions)... AND... you need that thread to store state that later requests can access Consider just storing it in the db as an ActiveRecord rather than trying to put it in a session. All in all easier to deal with, at least if your thread already was using ActiveRecord anyway (which supplies it's own headaches). Worth considering, it's a trade-off as to what sort of headaches you want to deal with. -- Posted via http://www.ruby-forum.com/. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
[Rails] Re: Can I update session variable in a new thread?
Jonathan Rochkind wrote: > > But it is do-able, although not easy, I don't think you can get away > with just trying to access the session array itself in a thread that's > out of the request loop. I'd add it's do-able ONLY if you are using a server-side session store. NOT if you are using the cookie store that's the new Rails default. With the cookie store there's simply no possible way to write to the session outside the request loop. So if you want to write to a session in a thread, you'd have to wait() on the thread before returning from your action, which might defeat the purpose you were trying to use the thread for in the first place. Also, if you are planning on using ActiveRecord in this thread, you've got to make sure to do a few other things to ensure your AR calls are thread-safe. Things which change slightly in different Rails versions, as Rails community has changed it's consensus on what sorts of threading are 'supported' in what ways. And ALSO, even aside from AR, I learned the hard way that (at least if you're using the standard 1.8 MRI ruby interpreter), if you want to send a thread off and let it keep going outside the request-loop, you'd really better set it's priority to -1, or it's going to end up interfering with your response being returned even though you don't think it should. Contrary to popular belief, it IS possible to do concurrent programming like this in Rails, in all versions. But it's a big pain in the neck. Don't do it unless you really have to (which I think I do in my situation), try to find another solution if possible. -- Posted via http://www.ruby-forum.com/. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
[Rails] Re: Can I update session variable in a new thread?
Sudhi Kulkarni wrote: > Then in one of the periodic update methods if I access the > session[:executing] it is not updated to "done". Is there a problem if I > try to update session variable in a different thread? Actually, this is precisely what I was trying to do in another thread here where Fred graciously helped me too. I'd advise NOT trying to use the session array Rails gives to you, but instead just telling the thread the sessionID, and ten doing all the session access yourself manually. That's what I'm doing. It's not TOO hard, although it inconveniently changes for Rails 2.2 vs. pre-Rails 2.2. See this: http://www.ruby-forum.com/topic/184782 And see if it makes any sense to you, or still seems worth it to you when you see what you must do. :) But it does seem to be working for me, with some basic unit tests. There's sadly one more added wrinkle with regard to race conditions when you start to deal with sessions like this, that can result in the main action over-writing the session data the thread tries to write, or vice-versa. I have a hacky way to minimize (although not totally eliminate that), that is Session-store agnostic. You can totally eliminate it if you're willing to hack the particular session store, as I believe Fred has also done for the AR store, but I think this is quickly getting beyond what you hoped would be an easy answer. But it is do-able, although not easy, I don't think you can get away with just trying to access the session array itself in a thread that's out of the request loop. -- Posted via http://www.ruby-forum.com/. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~--~~~~--~~--~--~---
[Rails] Re: Can I update session variable in a new thread?
On May 27, 4:36 am, Sudhi Kulkarni
wrote:
> Frederick Cheung wrote:
> How do I know whether rails has closed out and pushed the cookie back to
> client?
There's going to be a pretty narrow window after your action method
returns and before rails has got as far as session cleanup. I can't
think you'd gain anything by waiting for your thread to exit there
rather than in your action.
Fred
> If I add a join before exiting from the action something like
> below
>
> def execute
> t1 = Thread.new { #code
> session[:executing] ="done";
> }
>
> t1.join
> end
>
> In the above case the session variable is updated. How would I get this
> working if I want the session to be updated sometime later and still not
> in that function?
>
> Regards,
> Sudhindra
> --
> Posted viahttp://www.ruby-forum.com/.
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[Rails] Re: Can I update session variable in a new thread?
Frederick Cheung wrote:
> On May 26, 10:20�am, Sudhi Kulkarni
> wrote:
>> session[:executing] it is not updated to "done". Is there a problem if I
>> try to update session variable in a different thread?
>>
>
> If this ends up setting the session after rails has closed out the
> session (ie pushed it back into the db, or sent the cookie back to the
> client) then this won't work.
>
> Fred
How do I know whether rails has closed out and pushed the cookie back to
client? If I add a join before exiting from the action something like
below
def execute
t1 = Thread.new { #code
session[:executing] ="done";
}
t1.join
end
In the above case the session variable is updated. How would I get this
working if I want the session to be updated sometime later and still not
in that function?
Regards,
Sudhindra
--
Posted via http://www.ruby-forum.com/.
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[Rails] Re: Can I update session variable in a new thread?
On May 26, 10:20 am, Sudhi Kulkarni
wrote:
> Hi,
>
> I have a controller code which does the following
>
> t1= Thread.new {
> #some code
> session[:executing] = "done"
> }
>
> Then in one of the periodic update methods if I access the
> session[:executing] it is not updated to "done". Is there a problem if I
> try to update session variable in a different thread?
>
If this ends up setting the session after rails has closed out the
session (ie pushed it back into the db, or sent the cookie back to the
client) then this won't work.
Fred
> Regards,
> Sudhi
> --
> Posted viahttp://www.ruby-forum.com/.
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