Hi,
I'm using the BackgroundRb scheduler (http:// backgroundrb.rubyforge.org/172) w/ rails (I'm using the older version -- not the 1.0 release announced yesterday).
My understanding of BackgroundRb is that it creates a separate thread (divorced from http request/response) that can run a long-running process (LRP).
The idea is to allow a rails application to periodically check on the status of the LRP and (potentially) provide updates on a web-page to a user.
There is a bit of sample-code for BackgroundRb (http://www.infoq.com/ articles/BackgrounDRb) that demonstrates how the status of a LRP can be checked.
Here is sample-code from a worker class described in the link shown above:
class FooWorker < BackgrounDRb::Rails attr_reader :progress def do_work(args) @progress = 0 calculate_the_meaning_of_life(args) end def calculate_the_meaning_of_life(args) while @progress < 100 # calculations here @progress += 1 end end end
FooWorker functions properly in my hands (i.e. a sample web-page will gradually show an increase in the value of @progress up to 100%).
The problem, however, happens when I change the code in the method called calculate_the_meaning_of_life(args) found within FooWorker to have it write a large file. The idea is to have rails/the-web-page check on the status of the file-writing until it is completely done.
The problem is that the file-writing method seems to lock the @progress variable and I can't access @progress via my controller/ periodical-updater until the entire method (calculate_the_meaning_of_life(args)) is complete.
The method shown below (where I write a file) doesn't give me access to @progress until the file is completely written & closed.
This is part of my new FooWorker class file 1 def calculate_the_meaning_of_life(args) 2 e = Event.find_all_by_id(best, :limit => 500000) 3 @progress = 0.0 4 @file_name = "#{args[:user_name]}.csv" 5 open("/e1/public/csvs/#{@file_name}", "w") 6 e.each_with_index do |row, i| 7 f.puts((columns.map {|c| row.send(c[:accessor])}).join("$")) 8 @progress = 100.0 * (i.to_f / e.size.to_f) 9 end 10 end 11 @progress = 100 12 end 13 FooWorker.register
if I delete lines 5 and 10 (i.e. I remove the file-writing commands, then I have access to the @progress variable even while I'm iterating through the result set (e.each_with_index {|blah| blah blah }), but lines 5 and 10 block access.
Clearly, I'm doing something wrong (perhaps using the wrong file i/o method), but I'm not sure of how to fix the problem.
Any suggestions or explanations as to what I'm doing wrong are much appreciated.