Bug #2718

DRb mixing up function return values between PIDs after fork()

Added by rhythmx (Sean Bradly) about 11 years ago. Updated over 1 year ago.

Target version:
ruby -v:


The precise details are in the attached test case, but the basic version goes as such: Child pid 1 calls method_a() but gets the return value of method_b() that was called from child pid 2. This only happens if the parent process makes any remote DRb calls before the fork.

This issue showed up for me in 1.9.1 as well as 1.8.7 on x86, but not in x86_64.


drb_test_case.rb (1.48 KB) drb_test_case.rb rhythmx (Sean Bradly), 02/07/2010 03:52 AM
drb-handle-fork-2718.patch (1.73 KB) drb-handle-fork-2718.patch jeremyevans0 (Jeremy Evans), 08/27/2019 06:40 PM

Related issues

Has duplicate Ruby master - Bug #14471: DRb mixing up function return values between PIDs after fork()ClosedActions

Updated by mame (Yusuke Endoh) almost 11 years ago

  • Status changed from Open to Assigned
  • Assignee set to seki (Masatoshi Seki)


Sorry for late response, but I cannot reproduce on both 1.8.7-p249
and 1.9.1-p378.

I assign this issue to Masatoshi Seki, the maintainer for drb.
Seki-san, could you check this issue?

Yusuke Endoh


Updated by rhythmx (Sean Bradly) over 10 years ago

I just verified that this shows up for me in Ruby 1.8.7-p249 as well as 1.9.1-p378. It does seem to reproduce a lot more readily in 1.8, however.

Note that you must run the test script with at least one argument (the arg can be anything) to trigger the problem. With 0 arguments it skips the bug to show the known good case.


(o.0) xi:~/code $ rvm list

rvm rubies

ruby-1.8.6-p383 [ i386 ]
ruby-1.8.7-p174 [ i386 ]
ruby-1.8.7-p249 [ i386 ]

=> ruby-1.9.1-p378 [ i386 ]

(o.0) xi:~/code $ ruby ~/Downloads/drb_test_case.rb FAIL
a exiting
a exiting
a exiting
a ok
b ok
b ok
a exitinga exiting

b exiting
b exiting



Updated by jeremyevans0 (Jeremy Evans) over 1 year ago

  • Backport set to 2.5: UNKNOWN, 2.6: UNKNOWN
  • Description updated (diff)
  • Project changed from Backport191 to Ruby master

Updated by jeremyevans0 (Jeremy Evans) over 1 year ago

  • Has duplicate Bug #14471: DRb mixing up function return values between PIDs after fork() added

Updated by jeremyevans0 (Jeremy Evans) over 1 year ago

This issue still occurs in the master branch. Attached is a patch that fixes it by detecting changes in pid.


Updated by jeremyevans (Jeremy Evans) over 1 year ago

  • Status changed from Assigned to Closed

Applied in changeset git|d0ed935d5bf8c3fce9800742a36e44fb7f63dda4.

Fix some DRb issues (#2552)

  • Handle BasicObject in drb

Also fix a bug in rescue clause of any_to_s because sprintf
does not handle the %l modifier.

Fixes [Bug #7833]

  • Do not send a reply to the client if there is a connection error

This allows for normal TCP shutdown (fin-ack-fin-ack instead of

Patch from (Pierre-Alexandre Meyer).

Fixes [Bug #2339]

  • Detect fork and do not reuse forked connections in drb

This associates each DRbConn with a pid, and if the pid changes,
it closes any DRbConns in the pool with a pid that no longer
matches. This fixes DRb servers from sending messages intended
for one client to another client after forking.

Fixes [Bug #2718]
Fixes [Bug #14471]

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