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  1. Facter
  2. FACT-2682

facter -p returns NUL character on stdout when called from nested ruby on windows

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Normal
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: FACT 3.11.14, FACT 3.14.12
    • Component/s: Windows
    • Labels:
    • Environment:
    • Template:
    • Acceptance Criteria:
      • recursive shellouts including facter in the stack work without binary garbage in stdout
      • unmodified facter_task returns correct results
    • Team:
      Night's Watch
    • Story Points:
      2
    • Sprint:
      NW - 2020-07-08
    • Method Found:
      Customer Feedback
    • Release Notes:
      Bug Fix
    • Release Notes Summary:
      This ticket fixes facter misbehavior in case it is called from ruby process while a custom fact also executes a system command using backticks
    • QA Risk Assessment:
      Needs Assessment

      Description

      As result of the investigation into MODULES-10602 and FM-8887, it was found that facter misbehaves on windows when being called from another ruby process while at the same time also executing other processes:

      When deploying the following fact to C:\ProgramData\PuppetLabs\puppet\cache\lib\facter\debugg.rb

      Facter.add(:debugg) do
        setcode do
          puts `cmd /c echo bar`.inspect
        end
      end
      

      weird things start to happen:

      PS C:\> & 'C:\Program Files\Puppet Labs\Puppet\puppet\bin\irb.bat'
      irb(main):001:0>  `facter -p debugg`
      => "\x00\"bar\\n\"\n"
      irb(main):002:0>
      

      Note the \x00 at the start of the output. Replacing the backtick-call to cmd in the fact with a regular string makes the behaviour go away:

      Facter.add(:debugg) do
        setcode do
          puts "bar\n".inspect
        end
      end
      

      irb(main):002:0> `facter -p debugg`
      => "\n\"bar\\n\"\n"
      irb(main):003:0>
      

      Curiously, using Puppet::Util::Execution.execute for calling facter also does not show the issue:

      irb(main):004:0> Puppet::Util::Execution.execute("facter -p debugg")
      => "\n\"bar\\n\"\n"
      irb(main):005:0>
      

      I could verify that this is the cause for the behaviour seen in MODULES-10602 and FM-8887, and I could reproduce it with only the latest puppet-agent (6.16.0) installed on a windows server 2019 virtual box (gusztavvargadr/windows-server). Customers and SEs have reported seeing the same symptoms as far back as 2019.2.1.

      For a full-featured repro environment, the hydra demo environments work out of the box, as (amongst others) the chocolateyversion fact triggers the bug.

      I could not reproduce it on a litmusimage/centos:8 docker image with the same agent version:

      david@zion:~/git/puppetlabs-motd (master)$ docker exec -ti litmusimage_centos_8-2225 /bin/bash
      [root@40541a36d2a8 /]# cat /opt/puppetlabs/puppet/cache/lib/facter/debugg.rb
      Facter.add(:debugg) do
        setcode do
          #puts `cmd /c echo bar`.inspect
          puts `echo bar`.inspect
        end
      end
      [root@40541a36d2a8 /]# /opt/puppetlabs/puppet/bin/irb 
      irb(main):001:0> `facter -p debugg`
      => "\n\"bar\\n\"\n"
      irb(main):002:0> exit
      [root@40541a36d2a8 /]# puppet --version
      6.16.0
      [root@40541a36d2a8 /]# 
      

      https://github.com/puppetlabs/puppetlabs-facter_task/pull/125 has a workaround for the facter_task task. Since it is neither a straight up functional equivalent, nor keeps other tasks from breaking, I'm hesitant to commit that PR as a "fix" for this issue.

      See https://puppet.slack.com/archives/CF418R4BE/p1592905228073600 for extensive just-in-time debugging log.

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              Assignee:
              ciprian.badescu Ciprian Badescu
              Reporter:
              david.schmitt David Schmitt
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                Created:
                Updated:
                Resolved:

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