Rails - May 2005 - marshal session objects?

I''m sure many of you have hit that annoying SessionRestoreError:

   http://wiki.rubyonrails.com/rails/show/HowtoAvoidSessionRestoreError
   (and http://api.rubyonrails.com/classes/ActionController/Base.html in 
Sessions section)

The only good solution I''ve found for the problem (besides not storing 
objects in @session) is something like this:

   @session[''stored_object''] = Marshal.dump(my_object)

Then, to get it back:

   my_object = Marshal.load(@session[''stored_object''])

It really makes my life easier, so I thought I''d share it, and see if 
there''s any feedback about the idea.  There''s a performance
hit, I
suppose, but it only affects the controllers that do the marshaling.  I 
tend to use it in low traffic controllers (like for admin pages), so 
the performance isn''t an issue for me.

Another problem is that the code is a little more verbose, so I was 
wondering if it would be nice to have it built into rails.  Maybe 
controllers that want it would look like:

class MyController < ApplicationController
   marshal_session_objects
   model :my_class
   def index
     @session[''my_class''] = MyClass.new
   end
end

I don''t know if this would be useful, but I''d be happy to
start working
on a patch if it is..

Thanks,
Zach

On Wed, 18 May 2005, Zach Thompson wrote:
> I''m sure many of you have hit that annoying SessionRestoreError:
>
>  http://wiki.rubyonrails.com/rails/show/HowtoAvoidSessionRestoreError
>  (and http://api.rubyonrails.com/classes/ActionController/Base.html in 
> Sessions section)
>
> The only good solution I''ve found for the problem (besides not
storing
> objects in @session) is something like this:
>
>  @session[''stored_object''] = Marshal.dump(my_object)
>
> Then, to get it back:
>
>  my_object = Marshal.load(@session[''stored_object''])
>
> It really makes my life easier, so I thought I''d share it, and see
if there''s
> any feedback about the idea.  There''s a performance hit, I
suppose, but it
> only affects the controllers that do the marshaling.  I tend to use it in
low
> traffic controllers (like for admin pages), so the performance
isn''t an issue
> for me.
>
> Another problem is that the code is a little more verbose, so I was
wondering
> if it would be nice to have it built into rails.  Maybe controllers that
want
> it would look like:
>
> class MyController < ApplicationController
>  marshal_session_objects
>  model :my_class
>  def index
>    @session[''my_class''] = MyClass.new
>  end
> end
>
> I don''t know if this would be useful, but I''d be happy to
start working on a
> patch if it is..
>
> Thanks,
> Zach
i wrote the pstore backend to CGI::Session and this is exactly what it does -
only under flock/transaction control too.  i suspect there is a way to select
the cgi database manage under rails but have been too far from html-land to
recall.  if you look at the source of cgi/session/pstore.rb under the lib
directory of the ruby dist you''ll see this already implemented as a cgi
session manager.

hopefully this points you in the right direction - i''m slammed for the
next
week or so and can''t look further...

kind regards.

-a
-- 
==============================================================================|
email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple.  My religion is kindness.
| --Tenzin Gyatso
===============================================================================

I think I''m of the opinion that marshalling the session objects should
happen ''out of the box'' as the session simply fails if they
are not
marshalled/restored

-----Original Message-----
From: rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
[mailto:rails-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org] On
Behalf Of Zach Thompson
Sent: Thursday, 19 May 2005 12:21 PM
To: rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
Subject: [Rails] marshal session objects?

I''m sure many of you have hit that annoying SessionRestoreError:

   http://wiki.rubyonrails.com/rails/show/HowtoAvoidSessionRestoreError
   (and http://api.rubyonrails.com/classes/ActionController/Base.html in
Sessions section)

The only good solution I''ve found for the problem (besides not storing
objects in @session) is something like this:

   @session[''stored_object''] = Marshal.dump(my_object)

Then, to get it back:

   my_object = Marshal.load(@session[''stored_object''])

It really makes my life easier, so I thought I''d share it, and see if
there''s any feedback about the idea.  There''s a performance
hit, I
suppose, but it only affects the controllers that do the marshaling.  I
tend to use it in low traffic controllers (like for admin pages), so the
performance isn''t an issue for me.

Another problem is that the code is a little more verbose, so I was
wondering if it would be nice to have it built into rails.  Maybe
controllers that want it would look like:

class MyController < ApplicationController
   marshal_session_objects
   model :my_class
   def index
     @session[''my_class''] = MyClass.new
   end
end

I don''t know if this would be useful, but I''d be happy to
start working
on a patch if it is..

Thanks,
Zach

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On May 18, 2005, at 9:22 PM, Ara.T.Howard wrote:
> i wrote the pstore backend to CGI::Session and this is exactly what it  
> does -
> only under flock/transaction control too.  i suspect there is a way to  
> select
> the cgi database manage under rails but have been too far from  
> html-land to
> recall.  if you look at the source of cgi/session/pstore.rb under the  
> lib
> directory of the ruby dist you''ll see this already implemented as
a cgi
> session manager.
Thanks for pointing that out - it''s nice to see what''s going
on under
the hood of session management.  You can change the storage manager  
with this in environment.rb:

ActionController::CgiRequest::DEFAULT_SESSION_OPTIONS.update(: 
database_manager => CGI::Session::PStore)

I looked at the rails source, though, and it''s already using PStore as
the default storage manager...

Zach

On Thu, 19 May 2005, Zach Thompson wrote:
> On May 18, 2005, at 9:22 PM, Ara.T.Howard wrote:
>
>> i wrote the pstore backend to CGI::Session and this is exactly what it
does
>> -
>> only under flock/transaction control too.  i suspect there is a way to 
>> select
>> the cgi database manage under rails but have been too far from
html-land to
>> recall.  if you look at the source of cgi/session/pstore.rb under the
lib
>> directory of the ruby dist you''ll see this already implemented
as a cgi
>> session manager.
>
> Thanks for pointing that out - it''s nice to see what''s
going on under the
> hood of session management.  You can change the storage manager with this
in
> environment.rb:
>
> ActionController::CgiRequest::DEFAULT_SESSION_OPTIONS.update(: 
> database_manager => CGI::Session::PStore)
>
> I looked at the rails source, though, and it''s already using
PStore as the
> default storage manager...
>
> Zach
that''s what i thought too - but you weren''t able to store
arbitrary objects
though right?  the code you should would have double marshal''d
everything ;-)

weird no?

-a
-- 
==============================================================================|
email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple.  My religion is kindness.
| --Tenzin Gyatso
===============================================================================

On May 19, 2005, at 2:56 PM, Ara.T.Howard wrote:
> On Thu, 19 May 2005, Zach Thompson wrote:
>
>> On May 18, 2005, at 9:22 PM, Ara.T.Howard wrote:
>>
>>> i wrote the pstore backend to CGI::Session and this is exactly what
>>> it does -
>>> only under flock/transaction control too.  i suspect there is a way
>>> to select
>>> the cgi database manage under rails but have been too far from 
>>> html-land to
>>> recall.  if you look at the source of cgi/session/pstore.rb under 
>>> the lib
>>> directory of the ruby dist you''ll see this already
implemented as a
>>> cgi
>>> session manager.
>>
>> Thanks for pointing that out - it''s nice to see
what''s going on under
>> the hood of session management.  You can change the storage manager 
>> with this in environment.rb:
>>
>> ActionController::CgiRequest::DEFAULT_SESSION_OPTIONS.update(: 
>> database_manager => CGI::Session::PStore)
>>
>> I looked at the rails source, though, and it''s already using
PStore
>> as the default storage manager...
>>
>> Zach
>
> that''s what i thought too - but you weren''t able to store
arbitrary
> objects
> though right?  the code you should would have double marshal''d 
> everything ;-)
>
> weird no?
It''s always fun making computers do things like that... :)

I think what I''m talking about would actually need to work 
independently of whatever storage manager is being used for the 
session.  The problem occurs when there are two controllers, and the 
first stores an object in @session.  If the second controller doesn''t 
have the class definition for that object, then you get a Session 
Restore Error.  So I want to make it so that objects stay marshaled 
until the moment they are accessed - so the controller without the 
class definition would still work (since the marshaled object is just a 
String in @session).

Zach

On May 18, 2005, at 7:20 PM, Zach Thompson wrote:
> I''m sure many of you have hit that annoying SessionRestoreError:
>
>   http://wiki.rubyonrails.com/rails/show/HowtoAvoidSessionRestoreError
>   (and http://api.rubyonrails.com/classes/ActionController/Base.html 
> in Sessions section)
>
> The only good solution I''ve found for the problem (besides not
storing
> objects in @session) is something like this:
>
>   @session[''stored_object''] = Marshal.dump(my_object)
>
> Then, to get it back:
>
>   my_object = Marshal.load(@session[''stored_object''])
>
Ok - here''s a start..  You can stick this code in environment.rb and 
not have to worry about every controller having to require every class 
that is stored in @session.  The marshal occurs only when values in 
@session are accessed, so each controller can just require its own 
class definitions.  It kind of seems like a hack, but also seems to 
work:

class CGI
   class Session

     def [](key)
       unless @data
         @data = @dbman.restore
       end
       unless @used_data
         @used_data = {}
       end
       if @used_data[key]
         return @used_data[key]
       else
         val = @data[key]
         if val
           restored_val = Marshal.load(val)
           @used_data[key] = restored_val
           return restored_val
         end
       end
     end

     def []=(key, val)
       unless @write_lock
         @write_lock = true
       end
       unless @data
         @data = @dbman.restore
       end
       unless @used_data
         @used_data = {}
       end
       @used_data[key] = val
     end

     def update
       put_used_data_back
       @dbman.update
     end

     def close
       put_used_data_back
       @dbman.update
       @dbprot.clear
     end

     private
       def put_used_data_back
         @used_data && @used_data.each_pair do |key, val|
           @data[key] = Marshal.dump(val)
         end
       end

   end
end

Thanks for any feedback,
Zach