added lib/bootstrap.rb

.rubocop.yml

@@ -1250,6 +1250,7 @@ Style/MethodCallWithArgsParentheses:
     - add_development_dependency
     - catch
     - debug
+    - exit
     - expect
     - fail
     - gem
@@ -1260,6 +1261,7 @@ Style/MethodCallWithArgsParentheses:
     - pp
     - raise
     - require
+    - require_relative
     - skip
     - sleep
     - source
@@ -1268,6 +1270,7 @@ Style/MethodCallWithArgsParentheses:
     - throw
     - use
     - warn
+    - warn_and_exit
   AllowedPatterns: [^assert, ^refute]
 
 Style/MethodCallWithoutArgsParentheses:

lib/bootstrap.rb

@@ -0,0 +1,99 @@
+# This file is distributed under New Relic's license terms.
+# See https://github.com/newrelic/newrelic-ruby-agent/blob/main/LICENSE for complete details.
+# frozen_string_literal: true
+
+# This file is designed to bootstrap a `Bundler.require` based Ruby app (such as
+# a Ruby on Rails app) so that the app can be instrumented and observed by the
+# New Relic Ruby agent without the agent being added to the app as a dependency.
+#
+# Given a production-ready Ruby app that optionally has a pre-packaged "frozen"
+# or "deployment" based gem bundle, the New Relic Ruby agent can be introduced
+# to the app without modifying the app and keeping all of the app's content
+# read-only.
+#
+# Prerequisites:
+#   - Ruby (tested v2.4+)
+#   - Bundler (included with Ruby, tested v1.17+)
+#
+# Instructions:
+#   - First, make sure the New Relic Ruby agent exists on disk. For these
+#     instructions, we'll assume the agent exists at `/newrelic`.
+#     - The agent can be downloaded as the "newrelic_rpm" gem from RubyGems.org
+#       and unpacked with "gem unpack"
+#     - The agent can be cloned from the New Relic public GitHub repo:
+#       https://github.com/newrelic/newrelic-ruby-agent
+#   - Next, use the "RUBYOPT" environment variable to require ("-r") this
+#     file (note that the ".rb" extension is dropped):
+#       ```
+#       export RUBYOPT="-r /newrelic/lib/bootstrap"
+#       ```
+#   - Launch an existing Ruby app as usual. For a Ruby on Rails app, this might
+#     involve running `bin/rails server`.
+#   - In the Ruby app's directory, look for and inspect
+#     `log/newrelic_agent.log`. If this file exists and there are no "WARN" or
+#     "ERROR" entries within it, then the agent was successfully introduced to
+#     the Ruby application.
+
+module NRBundlerPatch
+  NR_AGENT_GEM = 'newrelic_rpm'
+
+  def require(*_groups)
+    super
+
+    require_newrelic
+  end
+
+  def require_newrelic
+    lib = File.dirname(__FILE__)
+    $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+    Kernel.require NR_AGENT_GEM
+  end
+end
+
+class NRBundlerPatcher
+  BUNDLER = 'bundler'
+  RUBYOPT = 'RUBYOPT'
+
+  def self.patch
+    check_for_require
+    check_for_rubyopt
+    check_for_bundler
+    Bundler::Runtime.prepend(NRBundlerPatch)
+  end
+
+  private
+
+  def self.check_for_require
+    warn_and_exit "#{__FILE__} is meant to be required, not invoked directly" if $PROGRAM_NAME == __FILE__
+  end
+
+  def self.check_for_rubyopt
+    unless ENV[RUBYOPT].to_s.match?("-r #{__FILE__.rpartition('.').first}")
+      warn_and_exit "#{__FILE__} is meant to be required via the RUBYOPT env var"
+    end
+  end
+
+  def self.check_for_bundler
+    require_bundler
+
+    warn_and_exit 'Required Ruby Bundler class Bundler::Runtime not defined!' unless defined?(Bundler::Runtime)
+
+    unless Bundler::Runtime.method_defined?(:require)
+      warn_and_exit "The active Ruby Bundler instance doesn't offer Bundler::Runtime#require"
+    end
+  end
+
+  def self.require_bundler
+    require BUNDLER
+  rescue LoadError => e
+    warn_and_exit "Required Ruby library '#{BUNDLER}' could not be required - #{e}"
+  end
+
+  def self.warn_and_exit(msg)
+    warn "New Relic entrypoint at #{__FILE__} encountered an issue:\n\t#{msg}"
+
+    exit 1
+  end
+end
+
+NRBundlerPatcher.patch

test/new_relic/bootstrap_test.rb

@@ -0,0 +1,134 @@
+# This file is distributed under New Relic's license terms.
+# See https://github.com/newrelic/newrelic-ruby-agent/blob/main/LICENSE for complete details.
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+
+class NewRelicBootstrapTest < Minitest::Test
+  class PhonyBundler
+    DEFAULT_GEM_NAME = 'tadpole'
+
+    def require(*_groups)
+      Kernel.require DEFAULT_GEM_NAME
+    end
+  end
+
+  def setup
+    require_bootstrap
+    monkeypatch_phony_bundler
+  end
+
+  def test_the_overall_prepend_based_monkeypatch
+    # Make sure that newrelic_rpm is required as a result of the patching
+    required_gems = []
+    Kernel.stub :require, proc { |gem| required_gems << gem } do
+      PhonyBundler.new.require
+    end
+
+    assert_equal 2, required_gems.size, "Expected 2 gems to be required, saw #{required_gems.size}."
+    assert_equal [PhonyBundler::DEFAULT_GEM_NAME, 'newrelic_rpm'], required_gems,
+      "Expected to see 'newrelic_rpm' required. Only saw #{required_gems}"
+  end
+
+  def test_check_for_require
+    opn = $PROGRAM_NAME
+
+    $PROGRAM_NAME = bootstrap_file
+    msg = ''
+    NRBundlerPatcher.stub :warn_and_exit, proc { |m| msg = m } do
+      NRBundlerPatcher.check_for_require
+    end
+
+    assert_match(/meant to be required, not invoked/, msg,
+      'Expected check_for_require to complain when bootstrap is invoked directly')
+  ensure
+    $PROGRAM_NAME = opn
+  end
+
+  def test_check_for_rubyopt
+    oro = ENV.fetch('RUBYOPT', nil)
+
+    ENV['RUBYOPT'] = "-r #{bootstrap_file}"
+
+    refute NRBundlerPatcher.check_for_rubyopt
+  ensure
+    ENV['RUBYOPT'] = oro if oro
+  end
+
+  def test_check_for_bundler_class_not_defined
+    oruntime = Bundler.send(:const_get, :Runtime)
+
+    NRBundlerPatcher.stub :require_bundler, nil do
+      Bundler.send(:remove_const, :Runtime)
+
+      msg = ''
+      NRBundlerPatcher.stub :warn_and_exit, proc { |m| msg = m; Bundler.send(:const_set, :Runtime, oruntime) } do
+        NRBundlerPatcher.check_for_bundler
+      end
+
+      assert_match(/class Bundler::Runtime not defined!/, msg,
+        'Expected check_for_bundler to complain if Bundler::Runtime is not defined')
+    end
+  ensure
+    Bundler.send(:const_set, :Runtime, oruntime)
+  end
+
+  def test_check_for_bundler_method_not_defined
+    skip_unless_minitest5_or_above
+
+    NRBundlerPatcher.stub :require_bundler, nil do
+      Bundler::Runtime.stub :method_defined?, false, [:require] do
+        msg = ''
+        NRBundlerPatcher.stub :warn_and_exit, proc { |m| msg = m } do
+          NRBundlerPatcher.check_for_bundler
+        end
+
+        assert_match(/doesn't offer Bundler::Runtime#require/, msg,
+          'Expected check_for_bundler to complain if Bundler::Runtime#require is not defined')
+      end
+    end
+  end
+
+  def test_require_bundler
+    skip_unless_minitest5_or_above
+
+    NRBundlerPatcher.stub :require, proc { |_gem| raise LoadError }, ['bundler'] do
+      msg = ''
+      NRBundlerPatcher.stub :warn_and_exit, proc { |m| msg = m } do
+        NRBundlerPatcher.check_for_bundler
+      end
+
+      assert_match(/could not be required/, msg,
+        'Expected require_bundler to complain if Bundler could not be required')
+    end
+  end
+
+  private
+
+  # Load the bootstrap file and anticipate the `warn` and `exit` calls
+  # with assertions
+  def require_bootstrap
+    assert_raises SystemExit do
+      assert_output(/New Relic entrypoint/) do
+        require_relative '../../lib/bootstrap'
+      end
+    end
+  end
+
+  # Have the patcher patch our phony Bundler instead of the real one
+  def monkeypatch_phony_bundler
+    NRBundlerPatcher.stub :check_for_require, nil do
+      NRBundlerPatcher.stub :check_for_rubyopt, nil do
+        NRBundlerPatcher.stub :check_for_bundler, nil do
+          Bundler::Runtime.stub :prepend, proc { |mod| PhonyBundler.prepend(mod) } do
+            NRBundlerPatcher.patch
+          end
+        end
+      end
+    end
+  end
+
+  def bootstrap_file
+    @bootstrap_file ||= File.expand_path('../../../lib/bootstrap.rb', __FILE__)
+  end
+end