Turn off const_missing patch

lib/new_relic/agent/agent.rb

@@ -8,7 +8,7 @@
 
 
 # This must be turned off before we ship
-VALIDATE_BACKGROUND_THREAD_LOADING = true
+VALIDATE_BACKGROUND_THREAD_LOADING = false
 
 # The NewRelic Agent collects performance data from ruby applications in realtime as the
 # application runs, and periodically sends that data to the NewRelic server.
@@ -362,12 +362,13 @@ def launch_worker_thread
 
       if VALIDATE_BACKGROUND_THREAD_LOADING
         require 'new_relic/agent/patch_const_missing'
+        self.class.newrelic_enable_warning
       end
 
       @worker_thread = Thread.new do
         begin
           if VALIDATE_BACKGROUND_THREAD_LOADING
-            self.class.new_relic_set_agent_thread(Thread.current)
+            self.class.newrelic_set_agent_thread(Thread.current)
           end          
           run_worker_loop
         rescue IgnoreSilentlyException

lib/new_relic/agent/patch_const_missing.rb

@@ -1,21 +1,31 @@
 # This class is for debugging purposes only.
 #
-class Class
-    
+class Module
+  @@newrelic_agent_thread = nil
   def new_relic_const_missing(*args)
-    if Thread.current == @agent_thread
-      STDERR.puts "Agent background thread shouldn't be calling const_missing!!!"
-      STDERR.puts caller.join("\n")
-      exit -1
+    if Thread.current == @@newrelic_agent_thread
+      msg = "Agent background thread shouldn't be calling const_missing (#{args.inspect})   \n"
+      msg << caller[0..4].join("   \n")
+      NewRelic::Config.instance.log.warn msg 
     end
-
     original_const_missing(*args)
   end
 
-  alias_method :original_const_missing, :const_missing
-  alias_method :const_missing, :new_relic_const_missing
+  def newrelic_enable_warning
+    Module.class_eval do
+      if !defined?(original_const_missing)
+        alias_method :original_const_missing, :const_missing
+        alias_method :const_missing, :new_relic_const_missing
+      end
+    end
+  end
+  def newrelic_disable_warning
+    Module.class_eval do
+      alias_method :const_missing, :original_const_missing if defined?(original_const_missing)
+    end
+  end
 
-  def new_relic_set_agent_thread(thread)
-    @agent_thread = thread
+  def newrelic_set_agent_thread(thread)
+    @@newrelic_agent_thread = thread
   end
 end

test/new_relic/agent/tc_agent.rb

@@ -57,6 +57,21 @@ def test_setup_log_default
     @agent.shutdown
   end
 
+  def test_classloading_patch
+    require 'new_relic/agent/patch_const_missing'
+    NewRelic::Agent::Agent.newrelic_set_agent_thread(Thread.current)
+    # try loading some non-existent class
+    NewRelic::Config.instance.log.expects(:warn).at_least_once.with{|args| args =~ /calling const_missing.*:FooBar/}
+    NewRelic::Config.instance.log.expects(:warn).with{|args| args =~ /calling const_missing.*:FooBaz/}.never
+    NewRelic::Agent::Agent.newrelic_enable_warning
+    assert_raise NameError do
+      FooBar::Bat
+    end
+    NewRelic::Agent::Agent.newrelic_disable_warning
+    assert_raise NameError do
+      FooBaz::Bat
+    end
+  end
   def test_info
     props = NewRelic::Config.instance.app_config_info
     list = props.assoc('Plugin List').last.sort