Backgroundrb devel - Oct 2006 - Session access interfers with other model access

Sorry to be such a bother but I''m not getting this.

I have two models: Emrec and Session (I''m using AR for session mgmt.) 
In my
worker I can access the Emrec model and delete a record, AS LONG AS I
don''t
try to access the Session model.  With the Session model access commented 
out as below, the Emrec record gets deleted.  If I uncomment those lines, 
the Emrec record is _not_ deleted.  Any idea what I''m doing wrong?

Thanks,
Bill


In my controller...

    @session_id = session.session_id
    session[:job_key] = MiddleMan.new_worker(:class => :foo_worker,
                                             :args => {:emrec_id => 
@emrec.id,
                                                           :session_id => 
@session_id})


In my worker...

  def do_work(args)
    @time_remaining = 7
    @emrec_id = args[:emrec_id]

    #@session_rec = Session.find(:first,
    #                       :conditions => ["sessid = ?", 
args[:session_id]])

    calculate_the_meaning_of_life(args)
    Emrec.delete(@emrec_id)
  end

Update...

I explicitly generated a Session model and that made things a little better. 
I can uncomment the lines below and now the Emrec DOES get deleted. 
However, if I try to also delete the Session record, neither gets deleted. 
Any ideas what gives?

Thanks,
Bill

----- Original Message ----- 
From: "Bill Walton" <bill.walton at charter.net>
To: "BackgroundRb" <backgroundrb-devel at rubyforge.org>
Sent: Tuesday, October 17, 2006 3:21 PM
Subject: [Backgroundrb-devel] Session access interfers with other 
modelaccess

> Sorry to be such a bother but I''m not getting this.
>
> I have two models: Emrec and Session (I''m using AR for session
mgmt.)  In
> my
> worker I can access the Emrec model and delete a record, AS LONG AS I 
> don''t
> try to access the Session model.  With the Session model access commented
> out as below, the Emrec record gets deleted.  If I uncomment those lines,
> the Emrec record is _not_ deleted.  Any idea what I''m doing wrong?
>
> Thanks,
> Bill
>
>
> In my controller...
>
>    @session_id = session.session_id
>    session[:job_key] = MiddleMan.new_worker(:class => :foo_worker,
>                                             :args => {:emrec_id =>
> @emrec.id,
>                                                           :session_id =>
> @session_id})
>
>
> In my worker...
>
>  def do_work(args)
>    @time_remaining = 7
>    @emrec_id = args[:emrec_id]
>
>    #@session_rec = Session.find(:first,
>    #                       :conditions => ["sessid = ?",
> args[:session_id]])
>
>    calculate_the_meaning_of_life(args)
>    Emrec.delete(@emrec_id)
>  end
> _______________________________________________
> Backgroundrb-devel mailing list
> Backgroundrb-devel at rubyforge.org
> http://rubyforge.org/mailman/listinfo/backgroundrb-devel
>

Are there any logs we can look at?  In dev mode we can see MySQL logs

On 10/17/06, Bill Walton <bill.walton at charter.net>
wrote:
>
> Update...
>
> I explicitly generated a Session model and that made things a little
> better.
> I can uncomment the lines below and now the Emrec DOES get deleted.
> However, if I try to also delete the Session record, neither gets deleted.
> Any ideas what gives?
>
> Thanks,
> Bill
>
> ----- Original Message -----
> From: "Bill Walton" <bill.walton at charter.net>
> To: "BackgroundRb" <backgroundrb-devel at rubyforge.org>
> Sent: Tuesday, October 17, 2006 3:21 PM
> Subject: [Backgroundrb-devel] Session access interfers with other
> modelaccess
>
>
> > Sorry to be such a bother but I''m not getting this.
> >
> > I have two models: Emrec and Session (I''m using AR for
session
> mgmt.)  In
> > my
> > worker I can access the Emrec model and delete a record, AS LONG AS I
> > don''t
> > try to access the Session model.  With the Session model access
> commented
> > out as below, the Emrec record gets deleted.  If I uncomment those
> lines,
> > the Emrec record is _not_ deleted.  Any idea what I''m doing
wrong?
> >
> > Thanks,
> > Bill
> >
> >
> > In my controller...
> >
> >    @session_id = session.session_id
> >    session[:job_key] = MiddleMan.new_worker(:class => :foo_worker,
> >                                             :args => {:emrec_id
=>
> > @emrec.id,
> >                                                           :session_id
=>
> > @session_id})
> >
> >
> > In my worker...
> >
> >  def do_work(args)
> >    @time_remaining = 7
> >    @emrec_id = args[:emrec_id]
> >
> >    #@session_rec = Session.find(:first,
> >    #                       :conditions => ["sessid = ?",
> > args[:session_id]])
> >
> >    calculate_the_meaning_of_life(args)
> >    Emrec.delete(@emrec_id)
> >  end
> > _______________________________________________
> > Backgroundrb-devel mailing list
> > Backgroundrb-devel at rubyforge.org
> > http://rubyforge.org/mailman/listinfo/backgroundrb-devel
> >
> _______________________________________________
> Backgroundrb-devel mailing list
> Backgroundrb-devel at rubyforge.org
> http://rubyforge.org/mailman/listinfo/backgroundrb-devel
>
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Sorry for the fat-fingered send earlier.

Further investigation reveals concrete evidence.  Just not sure what it 
means.  Sure would appreciate any insight / suggestions.  Code below.

I found that the backgroundrb.log was telling me it was encountering an 
error in the worker, trying to do a delete on a nil id.  What I''ve
found out
is this.

If I start a new browser (i.e., a new session) and point it to the app, the 
find in the worker fails and so the delete of the session record fails. 
Problem it, I can see the record (via MySQL-Front) in the table prior to the 
worker attempt to find it.  Why does the find fail?

If I restart the app (i.e., still using the same session id), the find in 
the worker SUCCEEDS, the session record is deleted, and a new (empty) 
session is created.  Why does the find succeed this time?  Is there 
something different about the session record at this point (like something I 
could _make_ happen)?  There''s no _visible_ difference.

Any ideas at all what might be going on here?  I''d be *real* happy to
send
along the view/layout and model if anybody''s willing to give it a quick
look.

TIA,
Bill



--------- Controller ------------

class CreateController < ApplicationController

  def index
    @emrec = Emrec.new
    @emrec.last_updated_at = Time.now
    @emrec.save
    @session_id = session.session_id
    session[:job_key] = MiddleMan.new_worker(:class => :foo_worker,
                                             :args => {:emrec_id => 
@emrec.id,
                                                       :session_id => 
@session_id})
    @session_rec_id = @session_id
  end

  def get_time_remaining
    if request.xhr?
      progress_percent = 
MiddleMan.get_worker(session[:job_key]).time_remaining
      render :update do |page|
        page.call(''progressPercent'',
''clock'', progress_percent)
        # commented-out to eliminate race condition on WinXP from debugging
        # page.redirect_to(:action => ''done'') if
progress_percent <= 0
      end
    else
      redirect_to :action => ''not_xhr''
    end
  end

  def done
    render :text => "Your FooWorker task has completed"
    MiddleMan.delete_worker(session[:job_key])
  end

end
----------- end Controller ------------

---------- worker -------------

class FooWorker < BackgrounDRb::Rails

  attr_reader :time_remaining

  def do_work(args)
    @time_remaining = 15
    @emrec_id = args[:emrec_id]
    @session_id = args[:session_id]
    @session_rec = Session.find(:first,
                            :conditions => ["sessid = ?",
@session_id])
    calculate_the_meaning_of_life(args)
    if !@session_rec.nil?
      Session.delete(@session_rec.id)
    end
    Emrec.delete(@emrec_id)
  end

  def calculate_the_meaning_of_life(args)
    while @time_remaining > 0
      @time_remaining -= 1
      sleep(1)
    end
  end

end
----- end worker ------

Bill Walton wrote:
>
> If I start a new browser (i.e., a new session) and
> point it to the app, the find in the worker fails and
> so the delete of the session record fails. Problem is,
> I can see the record (via MySQL-Front) in the table
> prior to the worker attempt to find it.  Why does the
> find fail?
I still do not understand why I can see the record in the table via 
MySQL-Front but Rails / BackgrounDRb cannot find it, but I figured out how 
to fix the problem.

Doing a session.update in the controller prior to the Middleman call somehow 
puts the record in a state where the find in the worker on the sessid field 
succeeds.

Hope this helps someone in the future.  If anybody can explain what''s
going
on with the session I''d be very interested to learn.

Best regards,
Bill

On Oct 19, 2006, at 6:19 AM, Bill Walton wrote:
>
> Bill Walton wrote:
>>
>> If I start a new browser (i.e., a new session) and
>> point it to the app, the find in the worker fails and
>> so the delete of the session record fails. Problem is,
>> I can see the record (via MySQL-Front) in the table
>> prior to the worker attempt to find it.  Why does the
>> find fail?
>
> I still do not understand why I can see the record in the table via
> MySQL-Front but Rails / BackgrounDRb cannot find it, but I figured  
> out how
> to fix the problem.
>
> Doing a session.update in the controller prior to the Middleman  
> call somehow
> puts the record in a state where the find in the worker on the  
> sessid field
> succeeds.
>
> Hope this helps someone in the future.  If anybody can explain  
> what''s going
> on with the session I''d be very interested to learn.
>
> Best regards,
> Bill

	Ahh good catch Bill. That makes total sense though. When you call  
the middleman from a rails action without doing the session.update,  
the session record is still in memory and not written to the db yet.  
update makes it write out the session into the db.

	Glad you got it working.

Cheers-
-- Ezra Zygmuntowicz 
-- Lead Rails Evangelist
-- ez at engineyard.com
-- Engine Yard, Serious Rails Hosting
-- (866) 518-YARD (9273)

Hi Ezra,

Ezra Zygmuntowicz wrote:
> When you call the middleman from a rails action without doing the 
> session.update, the session record is still in memory and not written to 
> the db yet.  update makes it write out the session into the db.
That''s not what it looks like.  What I mean is that I can _see_ the
record
in the database via MySQL-Front before the find is attempted.  Unless I very 
much misunderstand the way MySQL-Front works, the record has, in fact, 
already been written to the db.  Rails (or BackgrounDRb) just can''t
retrieve
it for some reason.
> Glad you got it working.
Thanks!  I just wish I understood _why_ it''s working.

Best regards,
Bill