# DRb::DRbBadScheme when using drbunix sockets, why?

**URL:** <https://www.ruby-forum.com/t/drb-drbbadscheme-when-using-drbunix-sockets-why/160299>\
**Category:** Ruby\
**Created:** [February 13, 2009, 11:06pm UTC](https://www.ruby-forum.com/t/drb-drbbadscheme-when-using-drbunix-sockets-why/160299 "2009-02-13T23:06:05Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![captaffy](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f04885/32.png) [@captaffy](https://www.ruby-forum.com/u/captaffy)\
**Post date:** [February 13, 2009, 11:06pm UTC](https://www.ruby-forum.com/t/drb-drbbadscheme-when-using-drbunix-sockets-why/160299/1 "2009-02-13T23:06:05Z")

</div>

Hi,

I’ve been slowly hacking on my parallel recursive readdir()  
implementation using a limited number of parallel processes, since as  
you all know, Ruby threads are not truly parallel.

Anyway, I’m now getting wierd errors like the following:

Starting DRb on server  
Exception `DRb::DRbBadScheme' at /usr/lib/ruby/1.8/drb/drb.rb:814 - drbunix:///tmp/stoffj-test_17986 Exception `DRb::DRbBadScheme’ at /usr/lib/ruby/1.8/drb/drb.rb:814 -  
drbunix:///tmp/stoffj-test\_17986  
Exception `DRb::DRbBadScheme’ at /usr/lib/ruby/1.8/drb/drb.rb:814 -  
drbunix:///tmp/stoffj-test\_17986  
counter.count=1

And it’s not really clear to my _why_ I’m getting these errors, or how I  
can trap them so I’m not bothered by them. The basic code uses both DRb  
and Slave libraries to make the interprocess communication simpler, and  
to have a central counting server to regulate the number of  
sub-processes I’ll be using at any one point in time.

So, first off, here’s a full set of output of my code on a test  
directory.

Thanks for any hints or suggestions. I _think_ I need to use begin …  
rescue … end blocks possibly, but it’s not clear where. Oh yeah, I’m  
running this all on a CentOS 5.2 (RHEL5.2) Final system, against a small  
350Mb test directory tree.

Thanks,  
John

------------------------------- log ----------------------------------

$ ./readdir-drb.rb tmp  
Starting DRb on server  
Exception `DRb::DRbBadScheme' at /usr/lib/ruby/1.8/drb/drb.rb:814 - drbunix:///tmp/stoffj-test_17986 Exception `DRb::DRbBadScheme’ at /usr/lib/ruby/1.8/drb/drb.rb:814 -  
drbunix:///tmp/stoffj-test\_17986  
Exception `DRb::DRbBadScheme' at /usr/lib/ruby/1.8/drb/drb.rb:814 - drbunix:///tmp/stoffj-test_17986 counter.count=1 Threaded! Exception `DRb::DRbBadScheme’ at /usr/lib/ruby/1.8/drb/drb.rb:814 -  
drbunix:///tmp/slave\_proc\_537506070\_17986\_17988\_0\_0.125356081811465  
Exception `DRb::DRbBadScheme' at /usr/lib/ruby/1.8/drb/drb.rb:814 - drbunix:///tmp/slave_proc_537506070_17986_17988_0_0.125356081811465 Exception `DRb::DRbBadScheme’ at /usr/lib/ruby/1.8/drb/drb.rb:814 -  
drbunix:///tmp/slave\_proc\_537506070\_17986\_17988\_0\_0.125356081811465  
Threaded!  
Exception `DRb::DRbBadScheme' at /usr/lib/ruby/1.8/drb/drb.rb:814 - drbunix:///tmp/slave_proc_537512250_17988_17989_0_0.20115187038118 Exception `DRb::DRbBadScheme’ at /usr/lib/ruby/1.8/drb/drb.rb:814 -  
drbunix:///tmp/slave\_proc\_537512250\_17988\_17989\_0\_0.20115187038118  
Exception `DRb::DRbBadScheme' at /usr/lib/ruby/1.8/drb/drb.rb:814 - drbunix:///tmp/slave_proc_537512250_17988_17989_0_0.20115187038118 size = 372104960 size = 373477128 Exception `NameError’ at /usr/lib/ruby/site\_ruby/1.8/slave.rb:409 -  
uninitialized constant Slave::DBb  
Exception `RuntimeError' at /usr/lib/ruby/site_ruby/1.8/slave.rb:519 - already shutdown exit (SystemExit) /usr/lib/ruby/site_ruby/1.8/slave.rb:265:in `exit’  
/usr/lib/ruby/site\_ruby/1.8/slave.rb:265:in `cling' /usr/lib/ruby/site_ruby/1.8/slave.rb:259:in `call’  
/usr/lib/ruby/site\_ruby/1.8/slave.rb:259:in `on_cut' /usr/lib/ruby/site_ruby/1.8/slave.rb:251:in `initialize’  
/usr/lib/ruby/site\_ruby/1.8/slave.rb:251:in `new' /usr/lib/ruby/site_ruby/1.8/slave.rb:251:in `on\_cut’  
/usr/lib/ruby/site\_ruby/1.8/slave.rb:265:in `cling' /usr/lib/ruby/site_ruby/1.8/slave.rb:415:in `initialize’  
/usr/lib/ruby/site\_ruby/1.8/slave.rb:593:in `new' /usr/lib/ruby/site_ruby/1.8/slave.rb:593:in `object’  
./readdir-drb.rb:114:in `readdir' ./readdir-drb.rb:86:in `foreach’  
./readdir-drb.rb:86:in `readdir’  
./readdir-drb.rb:207

Total size: 373477128 B  
Total size: 364723 KB  
Total size: 356 MB  
Total size: 0 GB  
Exception `Errno::ENOENT' at /usr/lib/ruby/1.8/fileutils.rb:1281 - No such file or directory - /tmp/slave_proc_537506070_17986_17988_0_0.125356081811465 Exception `RuntimeError’ at /usr/lib/ruby/site\_ruby/1.8/slave.rb:519 -  
already shutdown  
[rt3.taec.com](http://rt3.taec.com):~/src/Tools/philesight-20081120$ Exception `NameError' at /usr/lib/ruby/site_ruby/1.8/slave.rb:409 - uninitialized constant Slave::DBb Exception `Errno::ENOENT’ at /usr/lib/ruby/1.8/fileutils.rb:1281 - No  
such file or directory -  
/tmp/slave\_proc\_537512250\_17988\_17989\_0\_0.20115187038118  
Exception `IOError' at /usr/lib/ruby/1.8/drb/unix.rb:92 - stream closed Exception `Errno::EBADF’ at /usr/lib/ruby/1.8/drb/unix.rb:92 - Bad file  
descriptor - ///tmp/slave\_proc\_537512250\_17988\_17989\_0\_0.20115187038118  
/usr/lib/ruby/1.8/drb/unix.rb:92:in `close': Bad file descriptor - ///tmp/slave_proc_537512250_17988_17989_0_0.20115187038118 (Errno::EBADF) from /usr/lib/ruby/1.8/drb/unix.rb:92:in `close’  
from /usr/lib/ruby/1.8/drb/drb.rb:1433:in `run' from /usr/lib/ruby/1.8/drb/drb.rb:1427:in `start’  
from /usr/lib/ruby/1.8/drb/drb.rb:1427:in `run' from /usr/lib/ruby/1.8/drb/drb.rb:1347:in `initialize’  
from /usr/lib/ruby/1.8/drb/drb.rb:1627:in `new' from /usr/lib/ruby/1.8/drb/drb.rb:1627:in `start\_service’  
from /usr/lib/ruby/site\_ruby/1.8/slave.rb:396:in `initialize' ... 28 levels... from ./readdir-drb.rb:114:in `readdir’  
from ./readdir-drb.rb:86:in `foreach' from ./readdir-drb.rb:86:in `readdir’  
from ./readdir-drb.rb:207

## --------------------------- source

And here’s my source code, excuse my lack of Ruby knowledge, I’m a newb  
to Ruby, though not to programming. Hopefully that is shown. :]

#!/usr/bin/ruby

require ‘getoptlong’  
require ‘thread’  
require ‘slave’  
require ‘drb’  
require ‘drb/unix’

$VERSION = “v1.0”;  
$max\_slaves = 3  
$count = 50

# Local Socket - need to worry about multiple runs of this script, so

add on

# unique PID.

$URI = “drbunix:///tmp/stoffj-test\_” + Process.pid.to\_s

slave\_cnt\_mutex = Mutex.new

opts = GetoptLong.new(  
[“–help”, “-h”, GetoptLong::NO\_ARGUMENT],  
[“–kids”, “-k”, GetoptLong::REQUIRED\_ARGUMENT]  
)

#---------------------------------------------------------------------  
class Counter  
def initialize(max=1)  
@slaves = []  
@max = max  
@count = 1  
@count\_mutex = Mutex.new  
end

def count  
@count  
end

def max  
@max  
end

# Increment the count of slaves, returning 1 if incremented, 0 if not.

def increment  
ok = nil  
@count\_mutex.synchronize do  
if (@count \< @max) then  
@count += 1  
ok = 1  
end  
end  
ok  
end

# Decrement the count of slaves

def decrement  
@count\_mutex.synchronize do  
if (@count \> 1) then  
@count -= 1  
end  
end  
@count  
end  
end

#---------------------------------------------------------------------  
class ReadDir  
def initialize(server)  
@server = server

```
# Slave pool for this level of readdir() recursion.
@kids = []

```

end

def readdir(dir)

```
#puts "readdir(#{dir})"

size_file = {}
size_dir = {}
size_total = 0

# Traverse the directory and collect the size of all files and
# directories

begin
  Dir.foreach(dir) do |f|
    #print " #{f},"
    if(f != "." && f != "..") then
      f_full = addpath(dir, f)
      stat = File.lstat(f_full)

      if(!stat.symlink?) then

        if(stat.file?) then
          #puts " File: #{f}"
          size = File.size(f_full)
          size_file[f] = size
          size_total += size
        end

        if(stat.directory?) then
          #puts "DIR= #{f}"
          if (@server.max <= 1) then
            puts " no threads."
            size = readdir(f_full)
            if (size > 0) then
              size_dir[f] = size
              size_total += size
            end
          else
            ok = @server.increment
            if (ok)
              puts " Threaded!"
              @kids << Slave.object(:async => true) {
                size = readdir(f_full)
                puts "size = #{size}"
                # Duh... return the size from the slave properly
                size
              }
            else
              #puts " no free threads, do anyway"
              size = readdir(f_full)
              if(size > 0) then
                size_dir[f] = size
                size_total += size
              end
            end
          end
        end
      end
    end
  end
end

@kids.each { |kid|
  size_total += kid.value
}

#Puts "Dir: #{dir} = #{size_total}"
return size_total

```

end

end

#---------------------------------------------------------------------

# Read a directory and add to the database; this function is recursive

# for sub-directories

#---------------------------------------------------------------------  
def usage  
puts  
puts “usage: readdir-drb [–kids NUM] ”  
puts " defaults to #{$max\_kids} children"  
puts  
puts " version: #{$version}"  
puts  
end

#---------------------------------------------------------------------  
def addpath(a, b)  
return a + b if(a =~ //$/)  
return a + “/” + b  
end

#---------------------------------------------------------------------

# Main

#---------------------------------------------------------------------  
$DEBUG = true

opts.each do |opt,arg|  
case opt  
when “–kids”  
$max\_slaves = arg.to\_i  
else  
usage  
exit  
end  
end

if ARGV.length != 1  
puts “Missing dir argument (try --help)”  
exit 0  
end

dir = ARGV.shift

# Start the DRb service.

puts “Starting DRb on server”  
DRb.start\_service $URI, Counter.new($max\_slaves)

# Child

# Fire up the first slave process which will do the work of readdir()

DRb.start\_service  
counter = DRbObject.new\_with\_uri $URI

puts “counter.count=#{counter.count}”

# Fire up a new Kid Class readdir.

kid = ReadDir.new(counter)

# Now let’s try to do a recursive readdir() algorith with threads.

size = kid.readdir(dir)

sizekb = size / 1024;  
sizemb = sizekb / 1024;  
sizegb = sizemb / 1024;

puts “”  
puts “Total size: #{size} B”  
puts “Total size: #{sizekb} KB”  
puts “Total size: #{sizemb} MB”  
puts “Total size: #{sizegb} GB”

---

<div class="post-metadata">

**Author:** ![captaffy](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f04885/32.png) [@captaffy](https://www.ruby-forum.com/u/captaffy)\
**Post date:** [February 14, 2009, 12:53am UTC](https://www.ruby-forum.com/t/drb-drbbadscheme-when-using-drbunix-sockets-why/160299/2 "2009-02-14T00:53:19Z")

</div>

John Stoffel wrote:

> drbunix:///tmp/stoffj-test\_17986  
> Probably not helpful, but I thought it was more normal to represent that  
> file uri as:

drbunix:/tmp/stoffj-test\_17986

---

<div class="post-metadata">

**Author:** ![captaffy](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f04885/32.png) [@captaffy](https://www.ruby-forum.com/u/captaffy)\
**Post date:** [February 17, 2009, 5:27pm UTC](https://www.ruby-forum.com/t/drb-drbbadscheme-when-using-drbunix-sockets-why/160299/3 "2009-02-17T17:27:31Z")

</div>

John Stoffel wrote:

> Joel VanderWerf wrote:
> 
> > John Stoffel wrote:
> > 
> > > drbunix:///tmp/stoffj-test\_17986  
> > > Probably not helpful, but I thought it was more normal to represent that  
> > > file uri as:
> > 
> > drbunix:/tmp/stoffj-test\_17986
> 
> Hmmm, decent idea, but when I use this same URI in simpler,  
> non-recursive code, it works just fine. I’ll give it a whirl though and  
> let people know.
> 
> I was wondering if maybe I need to do some being rescue end blocks when  
> I open DRb sockets to catch system errors such as filled /tmp, etc?
> 
> Oh well… I’m getting back a consistent answer now, just lots of other  
> warnings and possible errors from DRb and the Slaves.
> 
> Cheers,  
> John

Well, I’ve got more information now. It struck me that the errors were  
NOT from my DRb code, but from the DRb calls made by the ‘slave’ module  
instead! So I pulled all my own DRb calls and re-configured my code to  
just use ‘slave’ module I found here:

[http://codeforpeople.com/lib/ruby/slave/](http://codeforpeople.com/lib/ruby/slave/)

using version 1.2.1 on a CentOS 5.2 system, with ruby 1.8.5 (2006-08-25)  
[i386-linux] so I suspect it’s possibly my Ruby version is too old, or  
the Slave module isn’t robust enough.

I guess I’ll re-post my code with some new ideas and comments.

Thanks,  
John

---

<div class="post-metadata">

**Author:** ![captaffy](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f04885/32.png) [@captaffy](https://www.ruby-forum.com/u/captaffy)\
**Post date:** [February 16, 2009, 1:24am UTC](https://www.ruby-forum.com/t/drb-drbbadscheme-when-using-drbunix-sockets-why/160299/4 "2009-02-16T01:24:49Z")

</div>

Joel VanderWerf wrote:

> John Stoffel wrote:
> 
> > drbunix:///tmp/stoffj-test\_17986  
> > Probably not helpful, but I thought it was more normal to represent that  
> > file uri as:
> 
> drbunix:/tmp/stoffj-test\_17986

Hmmm, decent idea, but when I use this same URI in simpler,  
non-recursive code, it works just fine. I’ll give it a whirl though and  
let people know.

I was wondering if maybe I need to do some being rescue end blocks when  
I open DRb sockets to catch system errors such as filled /tmp, etc?

Oh well… I’m getting back a consistent answer now, just lots of other  
warnings and possible errors from DRb and the Slaves.

Cheers,  
John