Improve InfluxDB backend location calculation

Using the stacktrace is not very nice and performant.
influxdb-rails offers a controller location already in Thread.current.
For the backend implementation we implemented a before filter
which stores the location in a similar fashion.

src/api/lib/backend/connection_helper.rb

@@ -1,3 +1,5 @@
+require 'remember_location'
+
 module Backend
   # Module that holds the wrapping methods for http requests, are mainly used for simplify the calculation of urls.
   #
@@ -40,6 +42,8 @@ module Backend
   #
 
   module ConnectionHelper
+    include Backend::RememberLocation
+
     private
 
     # Performs a http get request to the configured OBS Backend server.

src/api/lib/backend/instrumentation.rb

@@ -0,0 +1,49 @@
+module Backend
+  class Instrumentation
+    def initialize(http_method, host, http_status_code, runtime)
+      @http_method = http_method
+      @host = host
+      @http_status_code = http_status_code
+      @runtime = runtime
+    end
+
+    def instrument
+      return unless enabled?
+
+      ActiveSupport::Notifications.instrument('obs.backend.process_response', data)
+    end
+
+    private
+
+    attr_accessor :http_method, :host, :http_status_code, :runtime
+
+    def enabled?
+      CONFIG['influxdb_hosts'].present?
+    end
+
+    def data
+      {
+        http_method: http_method,
+        http_status_code: http_status_code,
+        host: host,
+        runtime: runtime,
+        controller_location: controller_location,
+        backend_location: backend_location
+      }
+    end
+
+    def controller_location
+      [
+        Thread.current[:_influxdb_rails_controller],
+        Thread.current[:_influxdb_rails_action]
+      ].reject(&:blank?).join('#')
+    end
+
+    def backend_location
+      [
+        Thread.current[:_influxdb_obs_backend_api_module],
+        Thread.current[:_influxdb_obs_backend_api_method]
+      ].reject(&:blank?).join('#')
+    end
+  end
+end

src/api/lib/backend/logger.rb

@@ -1,4 +1,4 @@
-require_relative '../influxdb_obs/obs/normalizer/location_normalizer'
+require_relative 'instrumentation'
 
 module Backend
   # Class that implements a logger to write output in the backend logs
@@ -20,7 +20,7 @@ def self.info(method, host, port, path, response, start_time)
       @backend_logger.info "#{now} #{method} #{host}:#{port}#{path} #{response.code} #{time_delta}"
       @backend_time += time_delta
       Rails.logger.debug "request took #{time_delta} #{@backend_time}"
-      instrument_notification(method, host, response.code, time_delta)
+      Backend::Instrumentation.new(method, host, response.code, time_delta).instrument
 
       return unless CONFIG['extended_backend_log']
 
@@ -33,20 +33,5 @@ def self.info(method, host, port, path, response, start_time)
         @backend_logger.info "(non-XML data) #{data.class}"
       end
     end
-
-    def self.instrument_notification(method, host, code, runtime)
-      return if CONFIG['influxdb_hosts'].blank?
-
-      location = InfluxDB::OBS::Normalizer::LocationNormalizer.new(caller_locations(4, 8))
-      data = {
-        http_method: method,
-        http_status: code,
-        host: host,
-        runtime: runtime,
-        controller: location.controller_name,
-        backend: location.backend_name
-      }
-      ActiveSupport::Notifications.instrument('obs.backend.process_response', data)
-    end
   end
 end

src/api/lib/backend/remember_location.rb

@@ -0,0 +1,25 @@
+module Backend
+  module RememberLocation
+    def singleton_method_added(method_name)
+      return if filtering.include?(method_name)
+      return if method_name == :singleton_method_added
+      return if method_name == :initialize
+
+      original_method = singleton_method(method_name)
+
+      filtering << method_name
+
+      define_singleton_method(method_name) do |*args, &block|
+        Thread.current[:_influxdb_obs_backend_api_method] = method_name.to_s
+        Thread.current[:_influxdb_obs_backend_api_module] = name
+        original_method.call(*args, &block)
+      end
+    end
+
+    private
+
+    def filtering
+      @filtering ||= []
+    end
+  end
+end

src/api/lib/influxdb_obs/obs/middleware/backend_subscriber.rb

@@ -25,7 +25,7 @@ def call(_name, _started, finished, _unique_id, data)
         attr_reader :series_name, :logger
 
         def enabled?
-          series_name.present?
+          CONFIG['influxdb_hosts'].present?
         end
 
         def values(runtime)
@@ -35,10 +35,10 @@ def values(runtime)
         def tags(data)
           {
             http_method: data[:http_method],
-            http_status: data[:http_status],
+            http_status_code: data[:http_status_code],
             host: data[:host],
-            controller: data[:controller],
-            backend: data[:backend]
+            controller_location: data[:controller_location],
+            backend_location: data[:backend_location]
           }.reject { |_, value| value.blank? }
         end
       end

src/api/spec/lib/backend/remember_location_spec.rb

@@ -0,0 +1,20 @@
+require 'rails_helper'
+
+RSpec.describe Backend::RememberLocation do
+  let(:mod) { WithRememberLocation }
+
+  class WithRememberLocation
+    extend Backend::RememberLocation
+
+    def self.run_after; end
+  end
+
+  describe 'it remembers the location' do
+    before do
+      mod.run_after
+    end
+
+    it { expect(Thread.current[:_influxdb_obs_backend_api_module]).to eq(mod.to_s) }
+    it { expect(Thread.current[:_influxdb_obs_backend_api_method]).to eq('run_after') }
+  end
+end

src/api/spec/lib/influx_db/obs/middleware/backend_subscriber_spec.rb

@@ -10,11 +10,11 @@
     let(:finish_time)  { Time.at(1_517_567_370) }
     let(:data) do
       {
-        http_status: 200,
+        http_status_code: 200,
         http_method: 'GET',
         host: 'backend',
-        controller: 'UsersController#index',
-        backend: 'Cloud#upload',
+        controller_location: 'UsersController#index',
+        backend_location: 'Cloud#upload',
         runtime: 2
       }
     end
@@ -25,16 +25,20 @@
           value: 2000
         },
         tags: {
-          http_status: 200,
+          http_status_code: 200,
           http_method: 'GET',
           host: 'backend',
-          controller: 'UsersController#index',
-          backend: 'Cloud#upload'
+          controller_location: 'UsersController#index',
+          backend_location: 'Cloud#upload'
         },
         timestamp: 1_517_567_370
       }
     end
 
+    before do
+      stub_const('CONFIG', CONFIG.merge('influxdb_hosts' => ['localhost']))
+    end
+
     it 'writes to InfluxDB' do
       expect_any_instance_of(InfluxDB::Client).to receive(:write_point).with(series_name, result)
       subject.call('_name', start_time, finish_time, '_unique_id', data)