Module: Datadog::Profiling::Ext::CPU

Defined in:
lib/ddtrace/profiling/ext/cpu.rb

Overview

Monkey patches Ruby’s ‘Thread` with our `Ext::CThread` to enable CPU-time profiling

Constant Summary collapse

ROLLBAR_INCOMPATIBLE_VERSIONS =

We cannot apply our CPU extension if a broken rollbar is around because that can cause customer apps to fail with a SystemStackError: stack level too deep.

This occurs whenever our extensions to Thread are applied BEFORE rollbar applies its own. This happens because a loop forms: our extension tries to call Thread#initialize, but it’s intercepted by rollbar, which then tries to call the original Thread#initialize as well, but instead alls our extension, leading to stack exhaustion.

See github.com/rollbar/rollbar-gem/pull/1018 for more details on the issue

Gem::Requirement.new('<= 3.1.1')

Class Method Summary collapse

Class Method Details

.apply! ⇒ Object 



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# File 'lib/ddtrace/profiling/ext/cpu.rb', line 22

def self.apply!
  return false unless supported?

  # Applying CThread to Thread will ensure any new threads
  # will provide a thread/clock ID for CPU timing.
  require 'ddtrace/profiling/ext/cthread'
  ::Thread.prepend(Profiling::Ext::CThread)
  ::Thread.singleton_class.prepend(Datadog::Profiling::Ext::WrapThreadStartFork)
end

.supported? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ddtrace/profiling/ext/cpu.rb', line 18

def self.supported?
  unsupported_reason.nil?
end

.unsupported_reason ⇒ Object 



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# File 'lib/ddtrace/profiling/ext/cpu.rb', line 32

def self.unsupported_reason
  # NOTE: Only the first matching reason is returned, so try to keep a nice order on reasons -- e.g. tell users
  # first that they can't use this on macOS before telling them that they have the wrong ffi version

  if RUBY_ENGINE == 'jruby'
    'JRuby is not supported'
  elsif RUBY_PLATFORM.include?('darwin')
    'Feature requires Linux; macOS is not supported'
  elsif RUBY_PLATFORM =~ /(mswin|mingw)/
    'Feature requires Linux; Windows is not supported'
  elsif !RUBY_PLATFORM.include?('linux')
    "Feature requires Linux; #{RUBY_PLATFORM} is not supported"
  elsif Gem::Specification.find_all_by_name('rollbar', ROLLBAR_INCOMPATIBLE_VERSIONS).any?
    'You have an incompatible rollbar gem version installed; ensure that you have rollbar >= 3.1.2 by ' \
    "adding `gem 'rollbar', '>= 3.1.2'` to your Gemfile or gems.rb file. " \
    'See https://github.com/rollbar/rollbar-gem/pull/1018 for details'
  elsif Gem::Specification.find_all_by_name('logging').any? && logging_inherit_context_enabled?
    'The `logging` gem is installed and its thread inherit context feature is enabled. ' \
    "Please add LOGGING_INHERIT_CONTEXT=false to your application's environment variables to disable the " \
    'conflicting `logging` gem feature. ' \
    'See https://github.com/TwP/logging/pull/230 for details'
  end
end