Use custom code for instrumenting method calls

The use of ActiveSupport would slow down instrumented method calls by
about 180x due to:

1. ActiveSupport itself not being the fastest thing on the planet
2. caller_locations() having quite some overhead

The use of caller_locations() has been removed because it's not _that_
useful since we already know the full namespace of receivers and the
names of the called methods.

The use of ActiveSupport has been replaced with some custom code that's
generated using eval() (which can be quite a bit faster than using
define_method).

This new setup results in instrumented methods only being about 35-40x
slower (compared to non instrumented methods).

1 files changed, 0 insertions, 42 deletions

diff --git a/lib/gitlab/metrics/subscribers/method_call.rb b/lib/gitlab/metrics/subscribers/method_call.rb
deleted file mode 100644
index 0094ed0dc6a..00000000000
--- a/lib/gitlab/metrics/subscribers/method_call.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-module Gitlab
-  module Metrics
-    module Subscribers
-      # Class for tracking method call timings.
-      class MethodCall < ActiveSupport::Subscriber
-        attach_to :method_call
-
-        SERIES = 'method_calls'
-
-        def instance_method(event)
-          return unless current_transaction
-
-          label = "#{event.payload[:module]}##{event.payload[:name]}"
-
-          add_metric(label, event.duration)
-        end
-
-        def class_method(event)
-          return unless current_transaction
-
-          label = "#{event.payload[:module]}.#{event.payload[:name]}"
-
-          add_metric(label, event.duration)
-        end
-
-        private
-
-        def add_metric(label, duration)
-          file, line = Metrics.last_relative_application_frame
-
-          values = { duration: duration, file: file, line: line }
-
-          current_transaction.add_metric(SERIES, values, method: label)
-        end
-
-        def current_transaction
-          Transaction.current
-        end
-      end
-    end
-  end
-end