Improved last_relative_application_frame timings

The previous setup wasn't exactly fast, resulting in instrumented method calls taking about 600 times longer than non instrumented calls (including any ActiveSupport code involved). With this commit this slowdown has been reduced to around 185 times.

Improved last_relative_application_frame timings
60a6a240 · Yorick Peterse · 141e946c · 60a6a240
Commit 60a6a240 authored Dec 10, 2015 by Yorick Peterse
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Showing with 8 additions and 5 deletions

metrics.rb lib/gitlab/metrics.rb +8 -5

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--- a/lib/gitlab/metrics.rb
+++ b/lib/gitlab/metrics.rb
 module Gitlab
  module Metrics
+    RAILS_ROOT   = Rails.root.to_s
+    METRICS_ROOT = Rails.root.join('lib', 'gitlab', 'metrics').to_s
+    PATH_REGEX   = /^#{RAILS_ROOT}\/?/
+
    def self.pool_size
      Settings.metrics['pool_size'] || 16
    end
@@ -20,16 +24,15 @@ module Gitlab
      @hostname
    end

+    # Returns a relative path and line number based on the last application call
+    # frame.
    def self.last_relative_application_frame
-      root    = Rails.root.to_s
-      metrics = Rails.root.join('lib', 'gitlab', 'metrics').to_s
-
      frame = caller_locations.find do |l|
-        l.path.start_with?(root) && !l.path.start_with?(metrics)
+        l.path.start_with?(RAILS_ROOT) && !l.path.start_with?(METRICS_ROOT)
      end

      if frame
-        return frame.path.gsub(/^#{Rails.root.to_s}\/?/, ''), frame.lineno
+        return frame.path.sub(PATH_REGEX, ''), frame.lineno
      else
        return nil, nil
      end