# ActiveRecord through Drb: problem with ids

**URL:** <https://www.ruby-forum.com/t/activerecord-through-drb-problem-with-ids/66440>\
**Category:** Ruby\
**Created:** [August 25, 2006, 3:58pm UTC](https://www.ruby-forum.com/t/activerecord-through-drb-problem-with-ids/66440 "2006-08-25T15:58:59Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![philpraxis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/77aa72/32.png) [@philpraxis](https://www.ruby-forum.com/u/philpraxis)\
**Post date:** [August 25, 2006, 3:58pm UTC](https://www.ruby-forum.com/t/activerecord-through-drb-problem-with-ids/66440/1 "2006-08-25T15:58:59Z")

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Hi,

I’m trying to use ActiveRecord objects through Drb, and I’m facing a  
strange thing:

Firstly, I’m using the following database:

* * *

## – SQL

CREATE TABLE gardens  
(  
lock\_version integer DEFAULT 0,  
id integer NOT NULL AUTO\_INCREMENT,  
name varchar(50),

PRIMARY KEY (id)  
) TYPE=INNODB;

CREATE TABLE flowers  
(  
lock\_version integer DEFAULT 0,  
id integer NOT NULL AUTO\_INCREMENT,  
garden\_id integer NOT NULL,  
name varchar(50),  
color varchar(50),

## PRIMARY KEY (id), FOREIGN KEY (garden\_id) REFERENCES gardens (id) ) TYPE=INNODB;

Now if I launch this server code:

* * *

## – Drb / ActiveRecord Server

#!/usr/local/bin/ruby  
require ‘rubygems’  
require ‘drb’  
require ‘active\_record’  
require ‘active\_record/transactions’

ActiveRecord::Base.establish\_connection(  
:adapter =\> “mysql”,  
:username =\> “root”,  
:host =\> “localhost”,  
:password =\> “”,  
:database =\> “flowers”  
)

# We build the ActiveRecord objects

class Garden \< ActiveRecord::Base  
include DRbUndumped  
has\_many :flowers  
end

class Flower \< ActiveRecord::Base  
include DRbUndumped  
belongs\_to :garden  
end

# We add some data

Garden.transaction do  
g = Garden.new(“name” =\> “garden1”)  
g.flowers \<\< Flower.new(“name” =\> “flower1”, “color” =\> “color1”)  
g.flowers \<\< Flower.new(“name” =\> “flower2”, “color” =\> “color2”)  
g.save  
g = Garden.new(“name” =\> “garden2”)  
g.flowers \<\< Flower.new(“name” =\> “flower3”, “color” =\> “color3”)  
g.save  
end

# We create the server and instanciate it

class Server  
def find(i)  
Garden.find(i)  
end  
end

s = Server.new

# We query the server

g = s.find(1)  
puts “#{g.id} | #{g.name}”  
g.flowers.each do |f|  
puts “#{f.id} | #{f.garden\_id} | #{f.name}”  
end

# We make the server available thruogh Drb

## DRb.start\_service(‘druby://localhost:9000’, s) DRb.thread.join

… I get what I was expecting, that is:

* * *

## 1 | garden1 1 | 1 | flower1 2 | 1 | flower2

Now I’m trying to call the server through Drb, with exactly the same  
code:

* * *

## – Drb / ActiveRecord Client, version 1

#!/usr/local/bin/ruby  
require ‘drb’

DRb.start\_service()  
obj = DRbObject.new(nil, ‘druby://localhost:9000’)

## g = obj.find(1) puts “#{g.id} | #{g.name}” g.flowers.each do |f| puts “#{f.id} | #{f.garden\_id} | #{f.name}” end

… I get:

* * *

## ar\_client.rb:8: warning: Object#id will be deprecated; use Object#object\_id 67884862 | garden1 ar\_client.rb:10: warning: Object#id will be deprecated; use Object#object\_id 67882632 | 1 | flower1 ar\_client.rb:10: warning: Object#id will be deprecated; use Object#object\_id 67880122 | 1 | flower2

Where do these warnings come from? And why these ids?

II follow the warning message, and change the code a little bit:

* * *

## – Drb / ActiveRecord Client, version 2

#!/usr/local/bin/ruby  
require ‘drb’

DRb.start\_service()  
obj = DRbObject.new(nil, ‘druby://localhost:9000’)

## g = obj.find(1) puts “#{g.object\_id} | #{g.name}” g.flowers.each do |f| puts “#{f.object\_id} | #{f.garden\_id} | #{f.name}” End

… I get:

* * *

## 67884862 | garden1 67882642 | 1 | flower1 67880142 | 1 | flower2

Warning disappeared, but Ids are still wrong.

Does anyone understand what happens here?

* * *

Philippe L., Ing. Dipl. EPFL  
Attik System  
rte de la Fonderie 2  
1700 Fribourg  
Switzerland  
[http://www.attiksystem.ch](http://www.attiksystem.ch)

Tel: +41 (26) 422 13 75  
Fax: +41 (26) 422 13 76

---

<div class="post-metadata">

**Author:** ![philpraxis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/77aa72/32.png) [@philpraxis](https://www.ruby-forum.com/u/philpraxis)\
**Post date:** [August 25, 2006, 4:45pm UTC](https://www.ruby-forum.com/t/activerecord-through-drb-problem-with-ids/66440/2 "2006-08-25T16:45:08Z")

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On Fri, 25 Aug 2006, Philippe L. wrote:

> … I get:
> 
> * * *
> 
> ## ar\_client.rb:8: warning: Object#id will be deprecated; use Object#object\_id 67884862 | garden1 ar\_client.rb:10: warning: Object#id will be deprecated; use Object#object\_id 67882632 | 1 | flower1 ar\_client.rb:10: warning: Object#id will be deprecated; use Object#object\_id 67880122 | 1 | flower2

certain methods are treated specially by drb. it was a mistake for  
rails to  
override Object#id for exatly this kind of scenario - many peice of code  
require it.

you need to do something like

class \<\< ActiveRecord  
alias “id\_\_”, “id”  
end

and then use this method.

> Warning disappeared, but Ids are still wrong.
> 
> Does anyone understand what happens here?

you are calling Object#id/object\_id - no ActiveRecord#id - check out the  
drb  
source to see why.

-a

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<div class="post-metadata">

**Author:** ![philpraxis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/77aa72/32.png) [@philpraxis](https://www.ruby-forum.com/u/philpraxis)\
**Post date:** [August 25, 2006, 4:47pm UTC](https://www.ruby-forum.com/t/activerecord-through-drb-problem-with-ids/66440/3 "2006-08-25T16:47:09Z")

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On Aug 25, 2006, at 9:56 AM, Philippe L. wrote:

> Warning disappeared, but Ids are still wrong.
> 
> Does anyone understand what happens here?

This is a total guess but it seems like DRB is not proxying  
the call to ‘id’ across the net to the remote object. Instead  
you seem to be getting the object\_id  
of the local proxy object instead of the Active Record version  
of ‘id’ from the real object at the server.

Warning, I don’t have any special knowledge of DRB or AR internals,  
this was just the first thing that came to mind when I saw your post.

Gary W.

---

<div class="post-metadata">

**Author:** ![philpraxis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/77aa72/32.png) [@philpraxis](https://www.ruby-forum.com/u/philpraxis)\
**Post date:** [August 27, 2006, 5:08pm UTC](https://www.ruby-forum.com/t/activerecord-through-drb-problem-with-ids/66440/4 "2006-08-27T17:08:43Z")

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On 25-aug-2006, at 16:38, removed\_email\_address@domain.invalid wrote:

> certain methods are treated specially by drb. it was a mistake for  
> rails to  
> override Object#id for exatly this kind of scenario - many peice of  
> code  
> require it.

Consdering that Object#id is marked deprecated - I think it was a  
good decision. I’d rather say it’s a problem with DrB that it doesn’t  
use object\_id instead

---

<div class="post-metadata">

**Author:** ![philpraxis](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/77aa72/32.png) [@philpraxis](https://www.ruby-forum.com/u/philpraxis)\
**Post date:** [September 4, 2006, 11:59pm UTC](https://www.ruby-forum.com/t/activerecord-through-drb-problem-with-ids/66440/5 "2006-09-04T23:59:19Z")

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hi,

I just found this thread because I had a similar problem. I don’t think  
it has something to do with drb, in fact my problem was that a “find” on  
an activerecord returned a nil object. Here is the gotcha : nil is still  
an object and has an id … which has nothing to do with database id’s.  
As ruby’s author knows it’s an usual pitfall, calling that method  
produces a warning.

I think the alias workaround is great, here is the syntax I used :

class ActiveRecord::Base  
alias\_method :id\_\_, :id  
end

This way you can use the method id\_\_ for any ActiveRecord::Base  
descendant. Useful to spot some bugs !