Drb recycled object problem

Ruby
1

I did a search on google and found the following page.
http://blade.nagaokaut.ac.jp/cgi-bin/vframe.rb/ruby/ruby-talk/13236?13221-13721
Going down on that page, you find a header saying ‘drb and “recycled
objects” error’.
I am having a similar error (recycled object, RangeError), but I don’t
understand the solution given here, and I was hoping someone could
explain to me what the solution is, and why it works. What is GCing?

Raj S.

2

Raj S. wrote:

As an addendum, I ran this guys test code on my comp and I didn’t get
any of his problems. So what causes the recycled object error now,
assuming the earlier problem was fixed?

Raj

3

Raj S. wrote:

bump?

4

[email protected] wrote:

GCing?
is maintained on the server.

-a
Ahh, that’s what recycled object means then. So how do I prevent the
object from being recycled until the server program is exited. Also,
why is the server recycling an object that is still in use?

Raj

5

Raj S. wrote:

could explain to me what the solution is, and why it works. What
to them
is maintained on the server.

-a
Ahh, that’s what recycled object means then. So how do I prevent the
object from being recycled until the server program is exited. Also,
why is the server recycling an object that is still in use?

Raj

Sorry for the double post. I should have done a little reading on the
GC module before asking that last question. Let me rephrase and instead
ask, is it wise to disable garbage collection at the beginning of a
program, then enable it when the program quits out? Seems to me that’s
asking for trouble unless you really know what you are doing.

6

On Tue, 27 Mar 2007, Raj S. wrote:

bump?

you have a handle on an object which has been garbage collected on the
server.
if you’re going to be serving objects you need to be sure a reference to
them
is maintained on the server.

-a

7

On Tue, 27 Mar 2007, Raj S. wrote:

enable it when the program quits out? Seems to me that’s asking for trouble
unless you really know what you are doing.

yeah. terrible idea.

you just need to keep a reference to it to prevent it from being gc’d.
can
you show use some code?

-a

8

[email protected] wrote:

yeah. terrible idea.

you just need to keep a reference to it to prevent it from being
gc’d. can
you show use some code?

-a
Snipping code would be tricky. It’s a fairly large program. None of
the objects that are important are ever, EVER, not referenced somehow.
Everything is stored in arrays, and transferred around in arrays.
Objects on the server are moved from array to array by the client
calling methods using DRb. What kind of code would you want me to show
you to prove this?

on the server

DRb.start_service($uri, server.game)

on the client

DRb.start_service
game = DRbObject.new(nil, “druby://#{ipfield.text}:#{$port}”) #
File.open($deck_dir + filefield.text.strip, “r”){|file|
game.add_player(namefield.text, file.gets)}

then the client operates by making repeated method calls on “game”

9

Raj S. wrote:
[…]

why is the server recycling an object that is still in use?
Doesn’t this message in the thread you mentioned help you?

http://blade.nagaokaut.ac.jp/cgi-bin/vframe.rb/ruby/ruby-talk/13293?13221-13721

Good luck.

10

On Tue, 27 Mar 2007, Raj S. wrote:

[email protected] wrote:

yeah. terrible idea.

you just need to keep a reference to it to prevent it from being gc’d. can
you show use some code?

-a

Snipping code would be tricky. It’s a fairly large program. None of the
objects that are important are ever, EVER, not referenced somehow.

but the error is telling you that this is exactly what’s happening?

Everything is stored in arrays, and transferred around in arrays. Objects
on the server are moved from array to array by the client calling methods
using DRb. What kind of code would you want me to show you to prove this?

it’s like this; there are two possibilities:

  1. you’ve found a bug in ruby and/or drb

  2. you are not actually keeping a reference on every object the
    client gets
    a remote reference on and some object(s) is being collected

given that drb is heavily used and mature it’s probably wise to spend
time
tracking down #2. if you’re going to look into #2 there is probably
help on
this list. basically you need to figure out which object is being lost
and
track its lifecycle on the server.

regards.

-a

11

On Tue, Mar 27, 2007 at 08:39:36PM +0900, Raj S. wrote:

Everything is stored in arrays, and transferred around in arrays.
Objects on the server are moved from array to array by the client
calling methods using DRb. What kind of code would you want me to show
you to prove this?

on the server

DRb.start_service($uri, server.game)

$foo = server.game
DRb.start_service($uri, $foo)

Keeping a reference to the object in global variable $foo is one way to
stop
it frm being garbage collected.

A local variable is fine, as long as it doesn’t drop out of scope: e.g.

foo = server.game
DRb.start_service($uri, foo)
DRb.thread.join # program waits here

12

On Wed, 28 Mar 2007, Brian C. wrote:

the objects that are important are ever, EVER, not referenced somehow.

Keeping a reference to the object in global variable $foo is one way to stop
it frm being garbage collected.

A local variable is fine, as long as it doesn’t drop out of scope: e.g.

foo = server.game
DRb.start_service($uri, foo)
DRb.thread.join # program waits here

drb itself holds a referent to this, the ‘front’, object - so i don’t
think
that’ll help too much. i’m guessing the game returns result objects of
some
type which are recycled in the server while the client tries to re-use
them.

cheers.

-a

13

[email protected] wrote:

cheers.

-a
Thanks guys. I’ll keep these tips in mind while I keep digging through
my code, trying to find if I let go of a reference somewhere.

Raj