Backgroundrb devel - Jul 2008 - Advanced Rails Recipe 43 doesn''t work, can''t figure a work around

Hello,

I''m trying to learn how to use BackgroundRB to run a long running
process while showing status to the user via a webpage.
1. I tried using Advanced Rails Recipe 43, however, it appears as though
backgroundrb has been updated since that book was published (2 months ago) as
methods like "register_status", "ask_stutus" no longer
exist.
2. I tried reading the everything on http://backgroundrb.rubyforge.org/
3. I tried to update the recipe code with what I learned from reading the
backgroundrb webpage
4. I failed spectacularly

Here''s my code reworked to be simpler:

---------------
class BillingWorker < BackgrounDRb::MetaWorker
  set_worker_name :billing_worker
  set_no_auto_load(true)

  def create(args = nil)
    cache[worker_key] = 0
    index = 0
    args.times do
      sleep(4)
      index = index + 1
      cache[worker_key] =(index * 100) / args
    end
    exit
  end
end

class PaymentsController < ApplicationController
  def async_test
    session[:job_key] = Bill.find(1).start_test
    redirect_to :action => ''check_async_test_status''
  end
  def check_async_test_status
    @percent_complete = Bill.test_status(session[:job_key])
    if request.xhr?
      if @percent_complete == 100
        render :update do |page|
          flash[:notice] = "test is complete"
          session[:job_key] = nil
          page.redirect_to :action => "pending"
        end
      else
        render :update do |page|
          page[:billingStatus].setStyle :width => "#{@percent_complete
*2}px"
          page[:billingStatus].replace_html "#{@percent_complete}%"
        end
      end
    end
  end
end

class Bill < ActiveRecord::Base
 def start_test
    MiddleMan.new_worker(:worker => :billing_worker, :worker_key =>
"foobar", :data => 5)
  end

  def self.test_status(job_key)
    MiddleMan.worker(:billing_worker, "foobar").ask_result(job_key)
    # also tried MiddleMan.worker(:billing_worker).ask_result(job_key)
  end
end
---------------

hitting /payments/async_test always results in
Packet::InvalidWorker
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.8/lib/packet/packet_connection.rb:52:in
`ask_worker''
/home/derrek/repos/prod/riderway/trunk/vendor/plugins/backgroundrb/server/lib/master_worker.rb:123:in
`get_result_object''

I can''t seem to get at the cache[worker_key] value.  Any help would be
greatly appreciated.

Thanks,
-Derrek

On Sun, Jul 20, 2008 at 12:14 AM, Derrek Long <derrek at ridecharge.com>
wrote:
> Hello,
>
> I''m trying to learn how to use BackgroundRB to run a long running
process while showing status to the user via a webpage.
> 1. I tried using Advanced Rails Recipe 43, however, it appears as though
backgroundrb has been updated since that book was published (2 months ago) as
methods like "register_status", "ask_stutus" no longer
exist.
Being one of the contributors for the recipe. I am terribly sorry for
this, but newer caching policies are a lot more stable. I am trying to
talk with Mike for releasing a new pdf that covers new version.

> 2. I tried reading the everything on http://backgroundrb.rubyforge.org/
> 3. I tried to update the recipe code with what I learned from reading the
backgroundrb webpage
> 4. I failed spectacularly
>
> Here''s my code reworked to be simpler:
>
> ---------------
> class BillingWorker < BackgrounDRb::MetaWorker
>  set_worker_name :billing_worker
>  set_no_auto_load(true)
>
>  def create(args = nil)
>    cache[worker_key] = 0
>    index = 0
>    args.times do
>      sleep(4)
>      index = index + 1
>      cache[worker_key] =(index * 100) / args
>    end
>    exit
>  end
> end
>
> class PaymentsController < ApplicationController
>  def async_test
>    session[:job_key] = Bill.find(1).start_test
>    redirect_to :action => ''check_async_test_status''
>  end
>  def check_async_test_status
>    @percent_complete = Bill.test_status(session[:job_key])
>    if request.xhr?
>      if @percent_complete == 100
>        render :update do |page|
>          flash[:notice] = "test is complete"
>          session[:job_key] = nil
>          page.redirect_to :action => "pending"
>        end
>      else
>        render :update do |page|
>          page[:billingStatus].setStyle :width =>
"#{@percent_complete *2}px"
>          page[:billingStatus].replace_html
"#{@percent_complete}%"
>        end
>      end
>    end
>  end
> end
>
> class Bill < ActiveRecord::Base
>  def start_test
>    MiddleMan.new_worker(:worker => :billing_worker, :worker_key =>
"foobar", :data => 5)
>  end
>
>  def self.test_status(job_key)
>    MiddleMan.worker(:billing_worker,
"foobar").ask_result(job_key)
>    # also tried MiddleMan.worker(:billing_worker).ask_result(job_key)
>  end
> end
> ---------------
>
> hitting /payments/async_test always results in
> Packet::InvalidWorker
>
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.8/lib/packet/packet_connection.rb:52:in
`ask_worker''
>
/home/derrek/repos/prod/riderway/trunk/vendor/plugins/backgroundrb/server/lib/master_worker.rb:123:in
`get_result_object''
>
> I can''t seem to get at the cache[worker_key] value.  Any help
would be greatly appreciated.
Two things are causing problem:

1. MiddleMan.new_worker(...) was not returning the "worker_key" with
which it was created and hence, your session[:job_key] was probably
wrong. I fixed it in latest git push and have added testcase to cover
that also, hence shouldn''t happen again.

2. Now, in your worker, you are using worker_key to cache the result:
cache[worker_key] = 0

Think of cache object as hash and whatever key you used here, must be
used while getting the results back and hence your code for fetching
the results should be:

MiddleMan.worker(:billing_worker,
"foobar").ask_result("foobar")

I got the same problem when I was trying to implement something in production,
having read the same Recipie. Exactly the same error in fact. I replicated it in
the rails console when trying to query the worker. Dropping out of the console
and starting again actually worked but of course doesn''t help when you
want to query straight away.

Packet::InvalidWorker

I got the impression that it was trying to query the worker just a fraction
before the worker was ready. I couldn''t gather much more information
than that. In the end I had to abandon BackgrounDRb for my project and use a
cronjob and basic queue due to time constraints, so I''d really like to
know what the problem was so that I don''t give up on BDRb alltogether.
I have to say I found the rubyforge site documentation far too lacking in
details so again I look forward to see more in depth examples.

If it is all fixed now then its a bit late for this project so maybe
I''ll give it another look for the next time it BDRb seems like an
appropriate solution.

RobL


hemant wrote:
> On Sun, Jul 20, 2008 at 12:14 AM, Derrek Long <derrek at
ridecharge.com> wrote:
>   
>> Hello,
>>
>> I''m trying to learn how to use BackgroundRB to run a long
running process while showing status to the user via a webpage.
>> 1. I tried using Advanced Rails Recipe 43, however, it appears as
though backgroundrb has been updated since that book was published (2 months
ago) as methods like "register_status", "ask_stutus" no
longer exist.
>>     
>
> Being one of the contributors for the recipe. I am terribly sorry for
> this, but newer caching policies are a lot more stable. I am trying to
> talk with Mike for releasing a new pdf that covers new version.
>
>
>   
>> 2. I tried reading the everything on http://backgroundrb.rubyforge.org/
>> 3. I tried to update the recipe code with what I learned from reading
the backgroundrb webpage
>> 4. I failed spectacularly
>>
>> Here''s my code reworked to be simpler:
>>
>> ---------------
>> class BillingWorker < BackgrounDRb::MetaWorker
>>  set_worker_name :billing_worker
>>  set_no_auto_load(true)
>>
>>  def create(args = nil)
>>    cache[worker_key] = 0
>>    index = 0
>>    args.times do
>>      sleep(4)
>>      index = index + 1
>>      cache[worker_key] =(index * 100) / args
>>    end
>>    exit
>>  end
>> end
>>
>> class PaymentsController < ApplicationController
>>  def async_test
>>    session[:job_key] = Bill.find(1).start_test
>>    redirect_to :action =>
''check_async_test_status''
>>  end
>>  def check_async_test_status
>>    @percent_complete = Bill.test_status(session[:job_key])
>>    if request.xhr?
>>      if @percent_complete == 100
>>        render :update do |page|
>>          flash[:notice] = "test is complete"
>>          session[:job_key] = nil
>>          page.redirect_to :action => "pending"
>>        end
>>      else
>>        render :update do |page|
>>          page[:billingStatus].setStyle :width =>
"#{@percent_complete *2}px"
>>          page[:billingStatus].replace_html
"#{@percent_complete}%"
>>        end
>>      end
>>    end
>>  end
>> end
>>
>> class Bill < ActiveRecord::Base
>>  def start_test
>>    MiddleMan.new_worker(:worker => :billing_worker, :worker_key
=> "foobar", :data => 5)
>>  end
>>
>>  def self.test_status(job_key)
>>    MiddleMan.worker(:billing_worker,
"foobar").ask_result(job_key)
>>    # also tried MiddleMan.worker(:billing_worker).ask_result(job_key)
>>  end
>> end
>> ---------------
>>
>> hitting /payments/async_test always results in
>> Packet::InvalidWorker
>>
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.8/lib/packet/packet_connection.rb:52:in
`ask_worker''
>>
/home/derrek/repos/prod/riderway/trunk/vendor/plugins/backgroundrb/server/lib/master_worker.rb:123:in
`get_result_object''
>>
>> I can''t seem to get at the cache[worker_key] value.  Any help
would be greatly appreciated.
>>     
>
> Two things are causing problem:
>
> 1. MiddleMan.new_worker(...) was not returning the "worker_key"
with
> which it was created and hence, your session[:job_key] was probably
> wrong. I fixed it in latest git push and have added testcase to cover
> that also, hence shouldn''t happen again.
>
> 2. Now, in your worker, you are using worker_key to cache the result:
> cache[worker_key] = 0
>
> Think of cache object as hash and whatever key you used here, must be
> used while getting the results back and hence your code for fetching
> the results should be:
>
> MiddleMan.worker(:billing_worker,
"foobar").ask_result("foobar")
> _______________________________________________
> Backgroundrb-devel mailing list
> Backgroundrb-devel at rubyforge.org
> http://rubyforge.org/mailman/listinfo/backgroundrb-devel
>

On Sun, Jul 20, 2008 at 1:32 AM, Rob Lacey <robl at
mail.pigdestroyer.co.uk> wrote:
> I got the same problem when I was trying to implement something in
> production, having read the same Recipie. Exactly the same error in fact. I
> replicated it in the rails console when trying to query the worker.
Dropping
> out of the console and starting again actually worked but of course
doesn''t
> help when you want to query straight away.
>
> Packet::InvalidWorker
>
> I got the impression that it was trying to query the worker just a fraction
> before the worker was ready. I couldn''t gather much more
information than
> that. In the end I had to abandon BackgrounDRb for my project and use a
> cronjob and basic queue due to time constraints, so I''d really
like to know
> what the problem was so that I don''t give up on BDRb alltogether.
I have to
> say I found the rubyforge site documentation far too lacking in details so
> again I look forward to see more in depth examples.
>
> If it is all fixed now then its a bit late for this project so maybe
I''ll
> give it another look for the next time it BDRb seems like an appropriate
> solution.
I have a fix for Linux for the above mentioned problem, looking for a
fix for OS X though. Basically, it boils down to "read_nonblock()"
doesn''t behave in OS X, as it should. In OSX, read_nonblock ,
*blocks*, hence we had to switch to recv_nonblock(), which doesn''t
block in both Linux and OS X. But recv_nonblock is a something of a
beast and doesn''t work well for newly created sockets.

> I have a fix for Linux for the above mentioned problem, looking for a
>fix for OS X though. Basically, it boils down to "read_nonblock()"
>doesn''t behave in OS X, as it should. In OSX, read_nonblock ,
>*blocks*, hence we had to switch to recv_nonblock(), which doesn''t
>block in both Linux and OS X. But recv_nonblock is a something of a
>beast and doesn''t work well for newly created sockets.
I pulled from git this morning and just spent another 20 minutes but
couldn''t get anything but the Packet::InvalidWorker error.  Is there
any example of working code I can look at that accesses the backgroundrb cache?

My system is Ubuntu 7.10, rails 2.1, and ruby 1.8.6.

Thanks,
-Derrek

On Mon, Jul 21, 2008 at 8:19 PM, Derrek Long <derrek at ridecharge.com>
wrote:
>> I have a fix for Linux for the above mentioned problem, looking for a
>>fix for OS X though. Basically, it boils down to
"read_nonblock()"
>>doesn''t behave in OS X, as it should. In OSX, read_nonblock ,
>>*blocks*, hence we had to switch to recv_nonblock(), which
doesn''t
>>block in both Linux and OS X. But recv_nonblock is a something of a
>>beast and doesn''t work well for newly created sockets.
>
> I pulled from git this morning and just spent another 20 minutes but
couldn''t get anything but the Packet::InvalidWorker error.  Is there
any example of working code I can look at that accesses the backgroundrb cache?
>
> My system is Ubuntu 7.10, rails 2.1, and ruby 1.8.6.
Please update to packet 0.1.9, it will work in Linux.