From 2e6b9abf054995b2a51009dfe678432be9087ba7 Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Wed, 14 Aug 2024 13:13:30 -0700
Subject: [PATCH 01/10] feat: Add experimental metrics to Rack

Emit http.server.request.duration metric if the application has the
metrics API installed and enables the feature via config
---
 .../lib/opentelemetry/instrumentation/base.rb | 15 ++++-
 .../instrumentation/rack/instrumentation.rb   |  4 +-
 .../rack/middlewares/event_handler.rb         | 58 +++++++++++++++++++
 3 files changed, 73 insertions(+), 4 deletions(-)

diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
index ddf828955..594e8c947 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
@@ -189,7 +189,7 @@ def infer_version
         end
       end
 
-      attr_reader :name, :version, :config, :installed, :tracer
+      attr_reader :name, :version, :config, :installed, :tracer, :meter
 
       alias installed? installed
 
@@ -205,9 +205,20 @@ def initialize(name, version, install_blk, present_blk,
         @installed = false
         @options = options
         @tracer = OpenTelemetry::Trace::Tracer.new
+        # Do we want to conditionally create a meter overall?
+        @meter = OpenTelemetry::Metrics::Meter.new if metrics_enabled?
       end
       # rubocop:enable Metrics/ParameterLists
 
+      def metrics_enabled?
+        # We need the API as a dependency to call metrics
+        # But, we can check for the SDK before we do any metrics-y things
+        # might be able to shore this up to run only on init to preven re-eval
+        result = defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
+        puts "***** metrics_enabled? result = #{result.inspect}"
+        result
+      end
+
       # Install instrumentation with the given config. The present? and compatible?
       # will be run first, and install will return false if either fail. Will
       # return true if install was completed successfully.
@@ -215,12 +226,12 @@ def initialize(name, version, install_blk, present_blk,
       # @param [Hash] config The config for this instrumentation
       def install(config = {})
         return true if installed?
-
         @config = config_options(config)
         return false unless installable?(config)
 
         instance_exec(@config, &@install_blk)
         @tracer = OpenTelemetry.tracer_provider.tracer(name, version)
+        @meter = OpenTelemetry.meter_provider.meter(name, version: version) if metrics_enabled?
         @installed = true
       end
 
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
index 3bfb68a3c..1bd811082 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
@@ -29,8 +29,8 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
         option :untraced_requests,        default: nil,   validate: :callable
         option :response_propagators,     default: [],    validate: :array
         # This option is only valid for applications using Rack 2.0 or greater
-        option :use_rack_events,          default: true, validate: :boolean
-
+        option :use_rack_events,          default: true,  validate: :boolean
+        option :send_metrics,             default: false, validate: :boolean
         # Temporary Helper for Sinatra and ActionPack middleware to use during installation
         #
         # @example Default usage
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
index 5475a4fc5..a49b3dee5 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
@@ -158,6 +158,43 @@ def untraced_request?(env)
             false
           end
 
+          def record_http_server_request_duration_metric(span)
+            return unless metrics_enabled? && http_server_duration_histogram
+            # find span duration
+            # end - start / a billion to convert nanoseconds to seconds
+            duration = (span.end_timestamp - span.start_timestamp) / 10**9
+            # Create attributes
+            #
+            attrs = {}
+            # pattern below goes
+            # stable convention
+            # current span convention
+
+            # attrs['http.request.method']
+            attrs['http.method'] = span.attributes['http.method']
+
+            # attrs['url.scheme']
+            attrs['http.scheme'] = span.attributes['http.scheme']
+
+            # same in stable semconv
+            attrs['http.route'] = span.attributes['http.route']
+
+            # attrs['http.response.status.code']
+            attrs['http.status_code'] = span.attributes['http.status_code']
+
+            # attrs['server.address'] ???
+            # attrs['server.port'] ???
+            # span includes host and port
+            attrs['http.host'] = span.attributes['http.host']
+
+            # attrs not currently in span payload
+            # attrs['network.protocol.version']
+            # attrs['network.protocol.name']
+            attrs['error.type'] = span.status.description if span.status.code == OpenTelemetry::Trace::Status::ERROR
+
+            http_server_duration_histogram.record(duration, attributes: attrs)
+          end
+
           # https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/data-http.md#name
           #
           # recommendation: span.name(s) should be low-cardinality (e.g.,
@@ -203,6 +240,7 @@ def detach_context(request)
             token, span = request.env[OTEL_TOKEN_AND_SPAN]
             span.finish
             OpenTelemetry::Context.detach(token)
+            record_http_server_request_duration_metric(span)
           rescue StandardError => e
             OpenTelemetry.handle_error(exception: e)
           end
@@ -247,6 +285,26 @@ def tracer
             OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.tracer
           end
 
+          def metrics_enabled?
+            OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.metrics_enabled?
+          end
+
+          def meter
+            # warn if no meter?
+            return @meter if defined?(@meter)
+            @meter = metrics_enabled? ? OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.meter : nil
+          end
+
+          def http_server_duration_histogram
+            # only want to make the view and the histogram once
+            # OpenTelemetry.meter_provider.add_view('http.server.request.duration', aggregation: OpenTelemetry::SDK::Metrics::Aggregation::ExplicitBucketHistogram.new(boundaries: [0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10]))
+            # Meter might be nil if metrics API isn't installed or isn't configured to send data
+            return @http_server_duration_histogram if defined?(@http_server_duration_histogram)
+
+            @http_server_duration_histogram = nil unless meter
+            @http_server_duration_histogram = meter.create_histogram('http.server.request.duration', unit: 's', description: 'Duration of HTTP server requests.')
+          end
+
           def config
             OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.config
           end

From 8338fc4da43f369e2210f4f0f5a313da5db34295 Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Wed, 14 Aug 2024 13:17:04 -0700
Subject: [PATCH 02/10] chore: Remove puts

---
 .../base/lib/opentelemetry/instrumentation/base.rb            | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
index 594e8c947..9bcfee5b7 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
@@ -214,9 +214,7 @@ def metrics_enabled?
         # We need the API as a dependency to call metrics
         # But, we can check for the SDK before we do any metrics-y things
         # might be able to shore this up to run only on init to preven re-eval
-        result = defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
-        puts "***** metrics_enabled? result = #{result.inspect}"
-        result
+        defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
       end
 
       # Install instrumentation with the given config. The present? and compatible?

From b031ceb8d308a1eda4e2655e23af2b0d43a82a9f Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Thu, 15 Aug 2024 15:33:57 -0700
Subject: [PATCH 03/10] chore: Misc

---
 .../base/lib/opentelemetry/instrumentation/base.rb  | 13 ++++++++-----
 .../rack/middlewares/event_handler.rb               | 11 +++++++++--
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
index 9bcfee5b7..13de6fea4 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
@@ -206,15 +206,17 @@ def initialize(name, version, install_blk, present_blk,
         @options = options
         @tracer = OpenTelemetry::Trace::Tracer.new
         # Do we want to conditionally create a meter overall?
-        @meter = OpenTelemetry::Metrics::Meter.new if metrics_enabled?
+        # @meter = OpenTelemetry::Metrics::Meter.new if metrics_enabled?
       end
       # rubocop:enable Metrics/ParameterLists
 
       def metrics_enabled?
-        # We need the API as a dependency to call metrics
-        # But, we can check for the SDK before we do any metrics-y things
-        # might be able to shore this up to run only on init to preven re-eval
-        defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
+        # We need the API as a dependency to call metrics-y things in instrumentation
+        # However, the user needs to install it separately from base, because we
+        # do not want base to rely on experimental code
+        return @metrics_enabled if defined?(@metrics_enabled)
+
+        @metrics_enabled ||= defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
       end
 
       # Install instrumentation with the given config. The present? and compatible?
@@ -224,6 +226,7 @@ def metrics_enabled?
       # @param [Hash] config The config for this instrumentation
       def install(config = {})
         return true if installed?
+
         @config = config_options(config)
         return false unless installable?(config)
 
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
index a49b3dee5..492b2809a 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
@@ -160,9 +160,10 @@ def untraced_request?(env)
 
           def record_http_server_request_duration_metric(span)
             return unless metrics_enabled? && http_server_duration_histogram
+
             # find span duration
             # end - start / a billion to convert nanoseconds to seconds
-            duration = (span.end_timestamp - span.start_timestamp) / 10**9
+            duration = (span.end_timestamp - span.start_timestamp) / (10**9)
             # Create attributes
             #
             attrs = {}
@@ -292,12 +293,18 @@ def metrics_enabled?
           def meter
             # warn if no meter?
             return @meter if defined?(@meter)
+
             @meter = metrics_enabled? ? OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.meter : nil
           end
 
           def http_server_duration_histogram
             # only want to make the view and the histogram once
-            # OpenTelemetry.meter_provider.add_view('http.server.request.duration', aggregation: OpenTelemetry::SDK::Metrics::Aggregation::ExplicitBucketHistogram.new(boundaries: [0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10]))
+            # OpenTelemetry.meter_provider.add_view(
+            #   'http.server.request.duration',
+            #   aggregation: OpenTelemetry::SDK::Metrics::Aggregation::ExplicitBucketHistogram.new(
+            #     boundaries: [0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10]
+            #     )
+            #   )
             # Meter might be nil if metrics API isn't installed or isn't configured to send data
             return @http_server_duration_histogram if defined?(@http_server_duration_histogram)
 

From ed4a354e96e7189ed0dbdb62172fa17987aa116b Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Mon, 19 Aug 2024 09:47:14 -0700
Subject: [PATCH 04/10] fix: Make sure duration is a float

Otherwise it may round to zero
---
 .../instrumentation/rack/middlewares/event_handler.rb           | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
index 492b2809a..b9b457805 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
@@ -163,7 +163,7 @@ def record_http_server_request_duration_metric(span)
 
             # find span duration
             # end - start / a billion to convert nanoseconds to seconds
-            duration = (span.end_timestamp - span.start_timestamp) / (10**9)
+            duration = (span.end_timestamp - span.start_timestamp) / Float(10**9)
             # Create attributes
             #
             attrs = {}

From a38aa875a1904e4f1974625c92030edcfb9eda6f Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Mon, 19 Aug 2024 15:08:34 -0700
Subject: [PATCH 05/10] feat: Create MetricsPatch modules to hold metrics

Like the Metrics ConfigurationPatch, include the MetricsPatch modules if
Metrics is enabled/present
---
 .../base/lib/opentelemetry/instrumentation.rb |  1 +
 .../lib/opentelemetry/instrumentation/base.rb | 26 ++++---
 .../instrumentation/metrics_patch.rb          | 21 ++++++
 .../instrumentation/rack/instrumentation.rb   |  7 ++
 .../rack/middlewares/event_handler.rb         | 67 ++-----------------
 .../rack/middlewares/metrics_patch.rb         | 58 ++++++++++++++++
 6 files changed, 108 insertions(+), 72 deletions(-)
 create mode 100644 instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
 create mode 100644 instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb

diff --git a/instrumentation/base/lib/opentelemetry/instrumentation.rb b/instrumentation/base/lib/opentelemetry/instrumentation.rb
index c02712b64..98b5e6f8f 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation.rb
@@ -7,6 +7,7 @@
 require 'opentelemetry'
 require 'opentelemetry-registry'
 require 'opentelemetry/instrumentation/base'
+require 'opentelemetry/instrumentation/metrics_patch' if defined?(OpenTelemetry::Metrics) # maybe also add Env var check?
 
 module OpenTelemetry
   # The instrumentation module contains functionality to register and install
diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
index 13de6fea4..a3a75d028 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
@@ -4,6 +4,9 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+# TODO: Maybe add an env var for globally enabling metrics as second switch?
+require_relative 'metrics_patch' if defined?(OpenTelemetry::Metrics)
+
 module OpenTelemetry
   module Instrumentation
     # The Base class holds all metadata and configuration for an
@@ -205,19 +208,12 @@ def initialize(name, version, install_blk, present_blk,
         @installed = false
         @options = options
         @tracer = OpenTelemetry::Trace::Tracer.new
-        # Do we want to conditionally create a meter overall?
-        # @meter = OpenTelemetry::Metrics::Meter.new if metrics_enabled?
+        create_meter
       end
       # rubocop:enable Metrics/ParameterLists
 
-      def metrics_enabled?
-        # We need the API as a dependency to call metrics-y things in instrumentation
-        # However, the user needs to install it separately from base, because we
-        # do not want base to rely on experimental code
-        return @metrics_enabled if defined?(@metrics_enabled)
-
-        @metrics_enabled ||= defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
-      end
+      # no-op, overridden in metrics patch
+      def create_meter; end
 
       # Install instrumentation with the given config. The present? and compatible?
       # will be run first, and install will return false if either fail. Will
@@ -232,10 +228,18 @@ def install(config = {})
 
         instance_exec(@config, &@install_blk)
         @tracer = OpenTelemetry.tracer_provider.tracer(name, version)
-        @meter = OpenTelemetry.meter_provider.meter(name, version: version) if metrics_enabled?
+        install_meter
         @installed = true
       end
 
+      # no-op, defined in metrics patch to use if metrics installed
+      def install_meter; end
+
+      # Metrics should not be enabled if we're trying to load them directly from base
+      def metrics_enabled?
+        false
+      end
+
       # Whether or not this instrumentation is installable in the current process. Will
       # be true when the instrumentation defines an install block, is not disabled
       # by environment or config, and the target library present and compatible.
diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb b/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
new file mode 100644
index 000000000..3450c1d36
--- /dev/null
+++ b/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
@@ -0,0 +1,21 @@
+module OpenTelemetry
+  module Instrumentation
+    module MetricsPatch
+      def create_meter
+        @meter = OpenTelemetry::Metrics::Meter.new
+      end
+
+      def install_meter
+        @meter = OpenTelemetry.meter_provider.meter(name, version: version) if metrics_enabled?
+      end
+
+      def metrics_enabled?
+        return @metrics_enabled if defined?(@metrics_enabled)
+
+        @metrics_enabled ||= defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
+      end
+    end
+  end
+end
+
+OpenTelemetry::Instrumentation::Base.prepend(OpenTelemetry::Instrumentation::MetricsPatch)
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
index 1bd811082..fb0102eb1 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
@@ -30,6 +30,7 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
         option :response_propagators,     default: [],    validate: :array
         # This option is only valid for applications using Rack 2.0 or greater
         option :use_rack_events,          default: true,  validate: :boolean
+        # TODO: This option currently exclusively uses the event handler, should we support old and new Rack?
         option :send_metrics,             default: false, validate: :boolean
         # Temporary Helper for Sinatra and ActionPack middleware to use during installation
         #
@@ -47,10 +48,16 @@ def middleware_args
           end
         end
 
+        # def metrics_enabled?
+        #   super
+        #   # other conditions unique to Rack? Like Events also being available?
+        # end
+
         private
 
         def require_dependencies
           require_relative 'middlewares/event_handler' if defined?(::Rack::Events)
+          require_relative 'middlewares/metrics_patch' if metrics_enabled?
           require_relative 'middlewares/tracer_middleware'
         end
 
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
index b9b457805..e1a0fb8c4 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
@@ -158,43 +158,8 @@ def untraced_request?(env)
             false
           end
 
-          def record_http_server_request_duration_metric(span)
-            return unless metrics_enabled? && http_server_duration_histogram
-
-            # find span duration
-            # end - start / a billion to convert nanoseconds to seconds
-            duration = (span.end_timestamp - span.start_timestamp) / Float(10**9)
-            # Create attributes
-            #
-            attrs = {}
-            # pattern below goes
-            # stable convention
-            # current span convention
-
-            # attrs['http.request.method']
-            attrs['http.method'] = span.attributes['http.method']
-
-            # attrs['url.scheme']
-            attrs['http.scheme'] = span.attributes['http.scheme']
-
-            # same in stable semconv
-            attrs['http.route'] = span.attributes['http.route']
-
-            # attrs['http.response.status.code']
-            attrs['http.status_code'] = span.attributes['http.status_code']
-
-            # attrs['server.address'] ???
-            # attrs['server.port'] ???
-            # span includes host and port
-            attrs['http.host'] = span.attributes['http.host']
-
-            # attrs not currently in span payload
-            # attrs['network.protocol.version']
-            # attrs['network.protocol.name']
-            attrs['error.type'] = span.status.description if span.status.code == OpenTelemetry::Trace::Status::ERROR
-
-            http_server_duration_histogram.record(duration, attributes: attrs)
-          end
+          # no-op, defined in MetricsPatch and required if metrics enabled
+          def record_http_server_request_duration_metric(span); end
 
           # https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/data-http.md#name
           #
@@ -286,31 +251,11 @@ def tracer
             OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.tracer
           end
 
-          def metrics_enabled?
-            OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.metrics_enabled?
-          end
-
-          def meter
-            # warn if no meter?
-            return @meter if defined?(@meter)
+          # no-op, overwritten by metrics patch if metrics is enabled
+          def meter; end
 
-            @meter = metrics_enabled? ? OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.meter : nil
-          end
-
-          def http_server_duration_histogram
-            # only want to make the view and the histogram once
-            # OpenTelemetry.meter_provider.add_view(
-            #   'http.server.request.duration',
-            #   aggregation: OpenTelemetry::SDK::Metrics::Aggregation::ExplicitBucketHistogram.new(
-            #     boundaries: [0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10]
-            #     )
-            #   )
-            # Meter might be nil if metrics API isn't installed or isn't configured to send data
-            return @http_server_duration_histogram if defined?(@http_server_duration_histogram)
-
-            @http_server_duration_histogram = nil unless meter
-            @http_server_duration_histogram = meter.create_histogram('http.server.request.duration', unit: 's', description: 'Duration of HTTP server requests.')
-          end
+          # no-op, overwritten by metrics patch if metrics is enabled
+          def http_server_request_duration_histogram; end
 
           def config
             OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.config
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb
new file mode 100644
index 000000000..8429bb167
--- /dev/null
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb
@@ -0,0 +1,58 @@
+module OpenTelemetry
+  module Instrumentation
+    module Rack
+      module Middlewares
+        module MetricsPatch
+          # Don't check in here to see if metrics is enabled, trust that if it's required, metrics will be enabled
+          def meter
+            OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.meter
+          end
+
+          def http_server_request_duration_histogram
+            # TODO: Add Advice to set small explicit histogram bucket boundaries
+            # TODO: Does this need to be memoized?
+            @http_server_request_duration_histogram ||= meter.create_histogram('http.server.request.duration', unit: 's', description: 'Duration of HTTP server requests.')
+          end
+
+          def record_http_server_request_duration_metric(span)
+            # find span duration
+            # end - start / a billion to convert nanoseconds to seconds
+            duration = (span.end_timestamp - span.start_timestamp) / Float(10**9)
+            # Create attributes
+            #
+            attrs = {}
+            # pattern below goes
+            # stable convention
+            # current span convention
+
+            # attrs['http.request.method']
+            attrs['http.method'] = span.attributes['http.method']
+
+            # attrs['url.scheme']
+            attrs['http.scheme'] = span.attributes['http.scheme']
+
+            # same in stable semconv
+            attrs['http.route'] = span.attributes['http.route']
+
+            # attrs['http.response.status.code']
+            attrs['http.status_code'] = span.attributes['http.status_code']
+
+            # attrs['server.address'] ???
+            # attrs['server.port'] ???
+            # span includes host and port
+            attrs['http.host'] = span.attributes['http.host']
+
+            # attrs not currently in span payload
+            # attrs['network.protocol.version']
+            # attrs['network.protocol.name']
+            attrs['error.type'] = span.status.description if span.status.code == OpenTelemetry::Trace::Status::ERROR
+
+            http_server_request_duration_histogram.record(duration, attributes: attrs)
+          end
+        end
+      end
+    end
+  end
+end
+
+OpenTelemetry::Instrumentation::Rack::Middlewares::EventHandler.prepend(OpenTelemetry::Instrumentation::Rack::Middlewares::MetricsPatch)

From 92d9ef6cf1bce0822c3d35e6ee8bdc1c80dfae7b Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Thu, 19 Sep 2024 17:33:43 -0700
Subject: [PATCH 06/10] style: Update comments, add file header

---
 .../instrumentation/metrics_patch.rb             | 10 ++++++++++
 .../rack/middlewares/metrics_patch.rb            | 16 +++++++++++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb b/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
index 3450c1d36..b479bf36c 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
@@ -1,5 +1,15 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
 module OpenTelemetry
   module Instrumentation
+    # MetricsPatch is a module that provides functionality to create a meter
+    # and record metrics if both the opentelemetry-metrics-api is present
+    # and the instrumentation to emit metrics has enabled metrics by setting
+    # :send_metrics to true
     module MetricsPatch
       def create_meter
         @meter = OpenTelemetry::Metrics::Meter.new
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb
index 8429bb167..b4c1299e1 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb
@@ -1,9 +1,18 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
 module OpenTelemetry
   module Instrumentation
     module Rack
       module Middlewares
+        # MetricsPatch is a module that provides functionality to record metrics
+        # if both the opentelemetry-metrics-api is present and the rack
+        # instrumentation is configured to emit metrics by setting
+        # :send_metrics to true
         module MetricsPatch
-          # Don't check in here to see if metrics is enabled, trust that if it's required, metrics will be enabled
           def meter
             OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.meter
           end
@@ -14,6 +23,7 @@ def http_server_request_duration_histogram
             @http_server_request_duration_histogram ||= meter.create_histogram('http.server.request.duration', unit: 's', description: 'Duration of HTTP server requests.')
           end
 
+          # TODO: Update this to define attributes based on SEMCONV_STABILITY_OPT_IN once available
           def record_http_server_request_duration_metric(span)
             # find span duration
             # end - start / a billion to convert nanoseconds to seconds
@@ -21,8 +31,8 @@ def record_http_server_request_duration_metric(span)
             # Create attributes
             #
             attrs = {}
-            # pattern below goes
-            # stable convention
+            # pattern below goes:
+            # # stable convention
             # current span convention
 
             # attrs['http.request.method']

From 3eef72a647bef5059382072d10425bd3f07b070d Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Thu, 3 Oct 2024 16:24:06 -0700
Subject: [PATCH 07/10] refactor: Switch from prepending to conditions

---
 .../base/lib/opentelemetry/instrumentation.rb |  1 -
 .../lib/opentelemetry/instrumentation/base.rb | 18 +++--
 .../instrumentation/metrics_patch.rb          | 31 ---------
 .../instrumentation/rack/instrumentation.rb   |  5 --
 .../rack/middlewares/event_handler.rb         | 43 +++++++++---
 .../rack/middlewares/metrics_patch.rb         | 68 -------------------
 6 files changed, 43 insertions(+), 123 deletions(-)
 delete mode 100644 instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
 delete mode 100644 instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb

diff --git a/instrumentation/base/lib/opentelemetry/instrumentation.rb b/instrumentation/base/lib/opentelemetry/instrumentation.rb
index 98b5e6f8f..c02712b64 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation.rb
@@ -7,7 +7,6 @@
 require 'opentelemetry'
 require 'opentelemetry-registry'
 require 'opentelemetry/instrumentation/base'
-require 'opentelemetry/instrumentation/metrics_patch' if defined?(OpenTelemetry::Metrics) # maybe also add Env var check?
 
 module OpenTelemetry
   # The instrumentation module contains functionality to register and install
diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
index a3a75d028..7972f2acb 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
@@ -4,8 +4,6 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-# TODO: Maybe add an env var for globally enabling metrics as second switch?
-require_relative 'metrics_patch' if defined?(OpenTelemetry::Metrics)
 
 module OpenTelemetry
   module Instrumentation
@@ -208,13 +206,11 @@ def initialize(name, version, install_blk, present_blk,
         @installed = false
         @options = options
         @tracer = OpenTelemetry::Trace::Tracer.new
-        create_meter
+        # check to see if the API is defined here because the config isn't available yet
+        @meter = OpenTelemetry::Metrics::Meter.new if defined?(OpenTelemetry::Metrics)
       end
       # rubocop:enable Metrics/ParameterLists
 
-      # no-op, overridden in metrics patch
-      def create_meter; end
-
       # Install instrumentation with the given config. The present? and compatible?
       # will be run first, and install will return false if either fail. Will
       # return true if install was completed successfully.
@@ -232,12 +228,14 @@ def install(config = {})
         @installed = true
       end
 
-      # no-op, defined in metrics patch to use if metrics installed
-      def install_meter; end
+      def install_meter
+        @meter = OpenTelemetry.meter_provider.meter(name, version: version) if metrics_enabled?
+      end
 
-      # Metrics should not be enabled if we're trying to load them directly from base
       def metrics_enabled?
-        false
+        return @metrics_enabled if defined?(@metrics_enabled)
+
+        @metrics_enabled ||= defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
       end
 
       # Whether or not this instrumentation is installable in the current process. Will
diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb b/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
deleted file mode 100644
index b479bf36c..000000000
--- a/instrumentation/base/lib/opentelemetry/instrumentation/metrics_patch.rb
+++ /dev/null
@@ -1,31 +0,0 @@
-# frozen_string_literal: true
-
-# Copyright The OpenTelemetry Authors
-#
-# SPDX-License-Identifier: Apache-2.0
-
-module OpenTelemetry
-  module Instrumentation
-    # MetricsPatch is a module that provides functionality to create a meter
-    # and record metrics if both the opentelemetry-metrics-api is present
-    # and the instrumentation to emit metrics has enabled metrics by setting
-    # :send_metrics to true
-    module MetricsPatch
-      def create_meter
-        @meter = OpenTelemetry::Metrics::Meter.new
-      end
-
-      def install_meter
-        @meter = OpenTelemetry.meter_provider.meter(name, version: version) if metrics_enabled?
-      end
-
-      def metrics_enabled?
-        return @metrics_enabled if defined?(@metrics_enabled)
-
-        @metrics_enabled ||= defined?(OpenTelemetry::Metrics) && @config[:send_metrics]
-      end
-    end
-  end
-end
-
-OpenTelemetry::Instrumentation::Base.prepend(OpenTelemetry::Instrumentation::MetricsPatch)
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
index fb0102eb1..31e5cebb6 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
@@ -48,16 +48,11 @@ def middleware_args
           end
         end
 
-        # def metrics_enabled?
-        #   super
-        #   # other conditions unique to Rack? Like Events also being available?
-        # end
 
         private
 
         def require_dependencies
           require_relative 'middlewares/event_handler' if defined?(::Rack::Events)
-          require_relative 'middlewares/metrics_patch' if metrics_enabled?
           require_relative 'middlewares/tracer_middleware'
         end
 
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
index e1a0fb8c4..0e17f6fa2 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
@@ -158,8 +158,6 @@ def untraced_request?(env)
             false
           end
 
-          # no-op, defined in MetricsPatch and required if metrics enabled
-          def record_http_server_request_duration_metric(span); end
 
           # https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/data-http.md#name
           #
@@ -251,12 +249,6 @@ def tracer
             OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.tracer
           end
 
-          # no-op, overwritten by metrics patch if metrics is enabled
-          def meter; end
-
-          # no-op, overwritten by metrics patch if metrics is enabled
-          def http_server_request_duration_histogram; end
-
           def config
             OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.config
           end
@@ -272,6 +264,41 @@ def create_span(parent_context, request)
             span.add_event('http.proxy.request.started', timestamp: request_start_time) unless request_start_time.nil?
             span
           end
+
+          # Metrics stuff
+          def metrics_enabled?
+            OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.metrics_enabled?
+          end
+
+          def meter
+            return unless metrics_enabled?
+
+            OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.meter
+          end
+
+          def http_server_request_duration_histogram
+            return unless metrics_enabled?
+
+            @http_server_request_duration_histogram ||= meter.create_histogram('http.server.request.duration', unit: 's', description: 'Duration of HTTP server requests.')
+          end
+
+          def record_http_server_request_duration_metric(span)
+            return unless metrics_enabled?
+            # find span duration
+            # end - start / a billion to convert nanoseconds to seconds
+            duration = (span.end_timestamp - span.start_timestamp) / Float(10**9)
+            # Create attributes
+            #
+            attrs = {}
+            attrs['http.method'] = span.attributes['http.method']
+            attrs['http.scheme'] = span.attributes['http.scheme']
+            attrs['http.route'] = span.attributes['http.route']
+            attrs['http.status_code'] = span.attributes['http.status_code']
+            attrs['http.host'] = span.attributes['http.host']
+            attrs['error.type'] = span.status.description if span.status.code == OpenTelemetry::Trace::Status::ERROR
+
+            http_server_request_duration_histogram.record(duration, attributes: attrs)
+          end
         end
       end
     end
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb
deleted file mode 100644
index b4c1299e1..000000000
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/metrics_patch.rb
+++ /dev/null
@@ -1,68 +0,0 @@
-# frozen_string_literal: true
-
-# Copyright The OpenTelemetry Authors
-#
-# SPDX-License-Identifier: Apache-2.0
-
-module OpenTelemetry
-  module Instrumentation
-    module Rack
-      module Middlewares
-        # MetricsPatch is a module that provides functionality to record metrics
-        # if both the opentelemetry-metrics-api is present and the rack
-        # instrumentation is configured to emit metrics by setting
-        # :send_metrics to true
-        module MetricsPatch
-          def meter
-            OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.meter
-          end
-
-          def http_server_request_duration_histogram
-            # TODO: Add Advice to set small explicit histogram bucket boundaries
-            # TODO: Does this need to be memoized?
-            @http_server_request_duration_histogram ||= meter.create_histogram('http.server.request.duration', unit: 's', description: 'Duration of HTTP server requests.')
-          end
-
-          # TODO: Update this to define attributes based on SEMCONV_STABILITY_OPT_IN once available
-          def record_http_server_request_duration_metric(span)
-            # find span duration
-            # end - start / a billion to convert nanoseconds to seconds
-            duration = (span.end_timestamp - span.start_timestamp) / Float(10**9)
-            # Create attributes
-            #
-            attrs = {}
-            # pattern below goes:
-            # # stable convention
-            # current span convention
-
-            # attrs['http.request.method']
-            attrs['http.method'] = span.attributes['http.method']
-
-            # attrs['url.scheme']
-            attrs['http.scheme'] = span.attributes['http.scheme']
-
-            # same in stable semconv
-            attrs['http.route'] = span.attributes['http.route']
-
-            # attrs['http.response.status.code']
-            attrs['http.status_code'] = span.attributes['http.status_code']
-
-            # attrs['server.address'] ???
-            # attrs['server.port'] ???
-            # span includes host and port
-            attrs['http.host'] = span.attributes['http.host']
-
-            # attrs not currently in span payload
-            # attrs['network.protocol.version']
-            # attrs['network.protocol.name']
-            attrs['error.type'] = span.status.description if span.status.code == OpenTelemetry::Trace::Status::ERROR
-
-            http_server_request_duration_histogram.record(duration, attributes: attrs)
-          end
-        end
-      end
-    end
-  end
-end
-
-OpenTelemetry::Instrumentation::Rack::Middlewares::EventHandler.prepend(OpenTelemetry::Instrumentation::Rack::Middlewares::MetricsPatch)

From 258b5874a640dfd9f9b88861f79b788ca4ecd418 Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Thu, 3 Oct 2024 16:31:22 -0700
Subject: [PATCH 08/10] refactor: Assign attributes using select

---
 .../rack/middlewares/event_handler.rb               | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
index 0e17f6fa2..f959031ec 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
@@ -266,6 +266,8 @@ def create_span(parent_context, request)
           end
 
           # Metrics stuff
+          HTTP_SERVER_REQUEST_DURATION_ATTRS_FROM_SPAN = %w[http.method http.scheme http.route http.status_code http.host].freeze
+
           def metrics_enabled?
             OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.metrics_enabled?
           end
@@ -287,14 +289,9 @@ def record_http_server_request_duration_metric(span)
             # find span duration
             # end - start / a billion to convert nanoseconds to seconds
             duration = (span.end_timestamp - span.start_timestamp) / Float(10**9)
-            # Create attributes
-            #
-            attrs = {}
-            attrs['http.method'] = span.attributes['http.method']
-            attrs['http.scheme'] = span.attributes['http.scheme']
-            attrs['http.route'] = span.attributes['http.route']
-            attrs['http.status_code'] = span.attributes['http.status_code']
-            attrs['http.host'] = span.attributes['http.host']
+            # glean attributes
+            attrs = span.attributes.select {|k, _v| HTTP_SERVER_REQUEST_DURATION_ATTRS_FROM_SPAN.include?(k) }
+            # set error
             attrs['error.type'] = span.status.description if span.status.code == OpenTelemetry::Trace::Status::ERROR
 
             http_server_request_duration_histogram.record(duration, attributes: attrs)

From ba9d06d8085cfbe36a61622698461a5db64b54d7 Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <87386821+kaylareopelle@users.noreply.github.com>
Date: Thu, 3 Oct 2024 16:58:37 -0700
Subject: [PATCH 09/10] style: Spacing updates

---
 .../base/lib/opentelemetry/instrumentation/base.rb       | 1 -
 .../instrumentation/rack/instrumentation.rb              | 2 +-
 .../instrumentation/rack/middlewares/event_handler.rb    | 9 ++++++---
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
index 7972f2acb..42c6f0bb3 100644
--- a/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
+++ b/instrumentation/base/lib/opentelemetry/instrumentation/base.rb
@@ -4,7 +4,6 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-
 module OpenTelemetry
   module Instrumentation
     # The Base class holds all metadata and configuration for an
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
index 31e5cebb6..91cd44577 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
@@ -32,6 +32,7 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
         option :use_rack_events,          default: true,  validate: :boolean
         # TODO: This option currently exclusively uses the event handler, should we support old and new Rack?
         option :send_metrics,             default: false, validate: :boolean
+
         # Temporary Helper for Sinatra and ActionPack middleware to use during installation
         #
         # @example Default usage
@@ -48,7 +49,6 @@ def middleware_args
           end
         end
 
-
         private
 
         def require_dependencies
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
index f959031ec..2bb9f6236 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
@@ -158,7 +158,6 @@ def untraced_request?(env)
             false
           end
 
-
           # https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/data-http.md#name
           #
           # recommendation: span.name(s) should be low-cardinality (e.g.,
@@ -281,7 +280,11 @@ def meter
           def http_server_request_duration_histogram
             return unless metrics_enabled?
 
-            @http_server_request_duration_histogram ||= meter.create_histogram('http.server.request.duration', unit: 's', description: 'Duration of HTTP server requests.')
+            @http_server_request_duration_histogram ||= meter.create_histogram(
+              'http.server.request.duration', 
+              unit: 's', 
+              description: 'Duration of HTTP server requests.'
+            )
           end
 
           def record_http_server_request_duration_metric(span)
@@ -290,7 +293,7 @@ def record_http_server_request_duration_metric(span)
             # end - start / a billion to convert nanoseconds to seconds
             duration = (span.end_timestamp - span.start_timestamp) / Float(10**9)
             # glean attributes
-            attrs = span.attributes.select {|k, _v| HTTP_SERVER_REQUEST_DURATION_ATTRS_FROM_SPAN.include?(k) }
+            attrs = span.attributes.select { |k, _v| HTTP_SERVER_REQUEST_DURATION_ATTRS_FROM_SPAN.include?(k) }
             # set error
             attrs['error.type'] = span.status.description if span.status.code == OpenTelemetry::Trace::Status::ERROR
 

From 7f8ce164182467381e9219fbebeee5dbc88cf79b Mon Sep 17 00:00:00 2001
From: Kayla Reopelle <kreopelle@newrelic.com>
Date: Thu, 3 Oct 2024 17:11:40 -0700
Subject: [PATCH 10/10] style: Rubocop

---
 .../instrumentation/rack/middlewares/event_handler.rb        | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
index 2bb9f6236..e7dd6a351 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb
@@ -281,14 +281,15 @@ def http_server_request_duration_histogram
             return unless metrics_enabled?
 
             @http_server_request_duration_histogram ||= meter.create_histogram(
-              'http.server.request.duration', 
-              unit: 's', 
+              'http.server.request.duration',
+              unit: 's',
               description: 'Duration of HTTP server requests.'
             )
           end
 
           def record_http_server_request_duration_metric(span)
             return unless metrics_enabled?
+
             # find span duration
             # end - start / a billion to convert nanoseconds to seconds
             duration = (span.end_timestamp - span.start_timestamp) / Float(10**9)