feat: Update metrics configuration patch (#1548)

* feat: Add configuration patch to set metrics exporter by environment variable

The environment variable has options for:
* console (default)
* otlp
* in-memory
* none

Like the Traces exporter, more than one exporter can be configured

* fix: Use updated class name for OTLP exporter

* feat: Update config patch for spec compliance

* Default option is now OTLP
* In-Memory option removed, it's not in the spec
* PeriodicMetricReader added for both Console and OTLP exporters
* Add the metrics OTLP exporter gem to the test gem group

* test: Remove setup/teardown tracer env var setting

* test: Update tests for JRuby

* style: Rubocop lines in block

---------

Co-authored-by: Matthew Wear <matthew.wear@gmail.com>

metrics_sdk/Gemfile

@@ -16,6 +16,7 @@ gem 'opentelemetry-sdk', path: '../sdk'
 gem 'opentelemetry-test-helpers', path: '../test_helpers'
 
 group :test, :development do
+  gem 'opentelemetry-exporter-otlp-metrics', path: '../exporter/otlp-metrics' unless RUBY_ENGINE == 'jruby'
   gem 'pry'
   gem 'pry-byebug' unless RUBY_ENGINE == 'jruby'
 end

metrics_sdk/lib/opentelemetry/sdk/metrics/configuration_patch.rb

@@ -10,12 +10,47 @@ module Metrics
       # The ConfiguratorPatch implements a hook to configure the metrics
       # portion of the SDK.
       module ConfiguratorPatch
+        def add_metric_reader(metric_reader)
+          @metric_readers << metric_reader
+        end
+
         private
 
-        # The metrics_configuration_hook method is where we define the setup process
-        # for metrics SDK.
+        def initialize
+          super
+          @metric_readers = []
+        end
+
+        # The metrics_configuration_hook method is where we define the setup process for the metrics SDK.
         def metrics_configuration_hook
           OpenTelemetry.meter_provider = Metrics::MeterProvider.new(resource: @resource)
+          configure_metric_readers
+        end
+
+        def configure_metric_readers
+          readers = @metric_readers.empty? ? wrapped_metric_exporters_from_env.compact : @metric_readers
+          readers.each { |r| OpenTelemetry.meter_provider.add_metric_reader(r) }
+        end
+
+        def wrapped_metric_exporters_from_env
+          exporters = ENV.fetch('OTEL_METRICS_EXPORTER', 'otlp')
+          exporters.split(',').map do |exporter|
+            case exporter.strip
+            when 'none' then nil
+            when 'console' then OpenTelemetry.meter_provider.add_metric_reader(Metrics::Export::PeriodicMetricReader.new(exporter: Metrics::Export::ConsoleMetricPullExporter.new))
+            when 'in-memory' then OpenTelemetry.meter_provider.add_metric_reader(Metrics::Export::InMemoryMetricPullExporter.new)
+            when 'otlp'
+              begin
+                OpenTelemetry.meter_provider.add_metric_reader(Metrics::Export::PeriodicMetricReader.new(exporter: OpenTelemetry::Exporter::OTLP::Metrics::MetricsExporter.new))
+              rescue NameError
+                OpenTelemetry.logger.warn 'The otlp metrics exporter cannot be configured - please add opentelemetry-exporter-otlp-metrics to your Gemfile, metrics will not be exported'
+                nil
+              end
+            else
+              OpenTelemetry.logger.warn "The #{exporter} exporter is unknown and cannot be configured, metrics will not be exported"
+              nil
+            end
+          end
         end
       end
     end

metrics_sdk/test/opentelemetry/sdk/metrics/configuration_patch_test.rb

@@ -0,0 +1,127 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'test_helper'
+require 'opentelemetry-exporter-otlp-metrics' unless RUBY_ENGINE == 'jruby'
+
+describe OpenTelemetry::SDK::Metrics::ConfiguratorPatch do
+  let(:configurator) { OpenTelemetry::SDK::Configurator.new }
+  let(:default_resource_attributes) do
+    {
+      'telemetry.sdk.name' => 'opentelemetry',
+      'telemetry.sdk.language' => 'ruby',
+      'telemetry.sdk.version' => OpenTelemetry::SDK::VERSION,
+      'process.pid' => Process.pid,
+      'process.command' => $PROGRAM_NAME,
+      'process.runtime.name' => RUBY_ENGINE,
+      'process.runtime.version' => RUBY_VERSION,
+      'process.runtime.description' => RUBY_DESCRIPTION,
+      'service.name' => 'unknown_service'
+    }
+  end
+
+  describe '#configure' do
+    describe 'meter_provider' do
+      it 'is an instance of SDK::Metrics::MeterProvider' do
+        configurator.configure
+
+        _(OpenTelemetry.meter_provider).must_be_instance_of(
+          OpenTelemetry::SDK::Metrics::MeterProvider
+        )
+      end
+    end
+
+    describe 'metric readers' do
+      it 'defaults to a periodic reader with an otlp exporter' do
+        skip 'OTLP exporter not compatible with JRuby' if RUBY_ENGINE == 'jruby'
+
+        configurator.configure
+
+        assert_equal 1, OpenTelemetry.meter_provider.metric_readers.size
+        reader = OpenTelemetry.meter_provider.metric_readers[0]
+
+        assert_instance_of OpenTelemetry::SDK::Metrics::Export::PeriodicMetricReader, reader
+        assert_instance_of OpenTelemetry::Exporter::OTLP::Metrics::MetricsExporter, reader.instance_variable_get(:@exporter)
+      end
+
+      it 'can be set by environment variable' do
+        OpenTelemetry::TestHelpers.with_env('OTEL_METRICS_EXPORTER' => 'console') do
+          configurator.configure
+        end
+
+        assert_equal 1, OpenTelemetry.meter_provider.metric_readers.size
+
+        reader = OpenTelemetry.meter_provider.metric_readers[0]
+
+        assert_instance_of OpenTelemetry::SDK::Metrics::Export::PeriodicMetricReader, reader
+        assert_instance_of OpenTelemetry::SDK::Metrics::Export::ConsoleMetricPullExporter, reader.instance_variable_get(:@exporter)
+      end
+
+      it 'supports "none" as an environment variable' do
+        OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
+          OpenTelemetry::TestHelpers.with_env('OTEL_METRICS_EXPORTER' => 'none') do
+            configurator.configure
+          end
+
+          assert_empty OpenTelemetry.meter_provider.metric_readers
+
+          refute_match(/The none exporter is unknown and cannot be configured/, log_stream.string)
+        end
+      end
+
+      it 'supports multiple exporters passed by environment variable' do
+        OpenTelemetry::TestHelpers.with_env('OTEL_METRICS_EXPORTER' => 'console,in-memory') do
+          configurator.configure
+        end
+
+        assert_equal 2, OpenTelemetry.meter_provider.metric_readers.size
+
+        reader1 = OpenTelemetry.meter_provider.metric_readers[0]
+        reader2 = OpenTelemetry.meter_provider.metric_readers[1]
+
+        assert_instance_of OpenTelemetry::SDK::Metrics::Export::PeriodicMetricReader, reader1
+        assert_instance_of OpenTelemetry::SDK::Metrics::Export::ConsoleMetricPullExporter, reader1.instance_variable_get(:@exporter)
+
+        assert_instance_of OpenTelemetry::SDK::Metrics::Export::InMemoryMetricPullExporter, reader2
+      end
+
+      it 'defaults to noop with invalid env var' do
+        OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
+          OpenTelemetry::TestHelpers.with_env('OTEL_METRICS_EXPORTER' => 'unladen_swallow') do
+            configurator.configure
+          end
+
+          assert_empty OpenTelemetry.meter_provider.metric_readers
+          assert_match(/The unladen_swallow exporter is unknown and cannot be configured/, log_stream.string)
+        end
+      end
+
+      it 'rescues NameErrors when otlp set to env var and the library is not installed' do
+        if RUBY_ENGINE == 'jruby'
+          OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
+            OpenTelemetry::TestHelpers.with_env('OTEL_METRICS_EXPORTER' => 'otlp') do
+              configurator.configure
+            end
+
+            assert_empty OpenTelemetry.meter_provider.metric_readers
+            assert_match(/The otlp metrics exporter cannot be configured - please add opentelemetry-exporter-otlp-metrics to your Gemfile, metrics will not be exported/, log_stream.string)
+          end
+        else
+          OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
+            OpenTelemetry::Exporter::OTLP::Metrics::MetricsExporter.stub(:new, -> { raise NameError }) do
+              OpenTelemetry::TestHelpers.with_env('OTEL_METRICS_EXPORTER' => 'otlp') do
+                configurator.configure
+              end
+
+              assert_empty OpenTelemetry.meter_provider.metric_readers
+              assert_match(/The otlp metrics exporter cannot be configured - please add opentelemetry-exporter-otlp-metrics to your Gemfile, metrics will not be exported/, log_stream.string)
+            end
+          end
+        end
+      end
+    end
+  end
+end

metrics_sdk/test/opentelemetry/sdk/metrics/meter_provider_test.rb

@@ -9,7 +9,11 @@
 describe OpenTelemetry::SDK::Metrics::MeterProvider do
   before do
     reset_metrics_sdk
-    OpenTelemetry::SDK.configure
+    # The MeterProvider tests deal with mock MetricReaders that are manually added
+    # Run the tests without the configuration patch interfering with the setup
+    OpenTelemetry::TestHelpers.with_env('OTEL_METRICS_EXPORTER' => 'none') do
+      OpenTelemetry::SDK.configure
+    end
   end
 
   describe '#meter' do

metrics_sdk/test/test_helper.rb

@@ -33,3 +33,6 @@ def with_test_logger
 ensure
   OpenTelemetry.logger = original_logger
 end
+
+# Suppress warn-level logs about a missing OTLP exporter for traces
+ENV['OTEL_TRACES_EXPORTER'] = 'none'