NameError: uninitialized constant RubyVM for non-CRuby

[eregon]

Check CONTRIBUTING guideline first and here is the list to help us investigate the problem.

Describe the bug
Starting fluentd on any other implementation than CRuby (e.g. TruffleRuby) causes:

$ bundle exec fluentd -c receiver.conf
bundler: failed to load command: fluentd (/home/eregon/.rubies/truffleruby-dev/bin/fluentd)
NameError: uninitialized constant RubyVM
  /home/eregon/.rubies/truffleruby-dev/lib/gems/gems/fluentd-1.12.3/bin/fluentd:4:in `const_missing'
  /home/eregon/.rubies/truffleruby-dev/lib/gems/gems/fluentd-1.12.3/bin/fluentd:4:in `<top (required)>'
  <internal:core> core/kernel.rb:400:in `load'
  <internal:core> core/kernel.rb:400:in `load'
  /home/eregon/.rubies/truffleruby-dev/bin/fluentd:23:in `<top (required)>'
  <internal:core> core/kernel.rb:400:in `load'
  <internal:core> core/kernel.rb:400:in `load'

due to

fluentd/bin/fluentd

Line 4 in 5bd3346

RubyVM::InstructionSequence.compile_option = {trace_instruction: false} rescue nil

#1764

To Reproduce
I used https://github.com/fluent/fluentd-benchmark/tree/master/one_forward but any fluent command would do

Expected behavior
It should work.

The rescue nil is not enough, for instance this also fails on CRuby:

$ ruby -ve 'RubyVM2::InstructionSequence.compile_option = {trace_instruction: false} rescue nil'
ruby 2.7.3p183 (2021-04-05 revision 6847ee089d) [x86_64-linux]
Traceback (most recent call last):
-e:1:in `<main>': uninitialized constant RubyVM2 (NameError)

I think the issue is the rescue nil only applies to {trace_instruction: false} and not the whole assignment.

Your Environment

• Fluentd or td-agent version: fluentd --version or td-agent --version: 1.12.3

[cosmo0920]

I'm not familiar with TruffleRuby. But, other C-Ruby implementation can be handle to install C extension such as cool.io, msgpack-ruby and other gems?
If so, we should investigate how to support TruffleRuby.

[eregon]

Yes, TruffleRuby supports C extensions: https://github.com/oracle/truffleruby/blob/master/doc/user/compatibility.md
I ran the one_forward benchmark on it (by commenting out that line) and it seems to work fine.
I also ran the test suite and a good part passes but not everything.

[cosmo0920]

I'd confirmed that truffleruby can handle C extensions.
But some gems are still not working correctly.
We should investigate more about this issue.

[ashie]

Fixed by #3376

[eregon]

Thank you for the fix!