fix: add meter provider implementation and tests

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

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module SDK
+    module Metrics
+      module Export
+        ExportError = Class.new(OpenTelemetry::Error)
+
+        # The operation finished successfully.
+        SUCCESS = 0
+
+        # The operation finished with an error.
+        FAILURE = 1
+
+        # The operation timed out.
+        TIMEOUT = 2
+      end
+    end
+  end
+end
+
+require 'opentelemetry/sdk/metrics/export/metric_reader'
+require 'opentelemetry/sdk/metrics/export/console_exporter'

metrics_sdk/lib/opentelemetry/sdk/metrics/export/console_exporter.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module SDK
+    module Metrics
+      module Export
+        class ConsoleExporter
+          PREFERRED_TEMPORALITY = 'delta'
+
+          def export(metrics)
+            puts metrics
+          end
+
+          def shutdown
+            SUCCESS
+          end
+
+          def preferred_temporality
+            PREFERRED_TEMPORALITY
+          end
+        end
+      end
+    end
+  end
+end
+

metrics_sdk/lib/opentelemetry/sdk/metrics/export/metric_reader.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module SDK
+    module Metrics
+      module Export
+        class MetricReader
+          def initialize(exporter)
+            @exporter = exporter
+          end
+
+          def collect; end
+
+          def shutdown(timeout: nil)
+            SUCCESS
+          end
+        end
+      end
+    end
+  end
+end
+

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

@@ -14,22 +14,106 @@ class MeterProvider < OpenTelemetry::Metrics::MeterProvider
         Key = Struct.new(:name, :version)
         private_constant(:Key)
 
-        def initialize
+        def initialize(resource: OpenTelemetry::SDK::Resources::Resource.create)
+          @mutex = Mutex.new
           @registry = {}
-          @registry_mutex = Mutex.new
+          @stopped = false
+
+          @metric_readers = []
+          @views = []
         end
 
         # Returns a {Meter} instance.
         #
-        # @param [optional String] name Instrumentation package name
+        # @param [String] name Instrumentation package name
         # @param [optional String] version Instrumentation package version
         #
         # @return [Meter]
-        def meter(name = nil, version = nil)
-          name ||= ''
+        def meter(name, version = nil)
           version ||= ''
-          OpenTelemetry.logger.warn 'calling MeterProvider#meter without providing a meter name.' if name.empty?
-          @registry_mutex.synchronize { @registry[Key.new(name, version)] ||= Meter.new(name, version) }
+          if @stopped
+            OpenTelemetry.logger.warn 'calling MeterProvider#meter after shutdown, a noop meter will be returned.'
+            OpenTelemetry::Metrics::Meter.new
+          else
+            @mutex.synchronize { @registry[Key.new(name, version)] ||= Meter.new(name, version, self) }
+          end
+        end
+
+        # Attempts to stop all the activity for this {MeterProvider}.
+        #
+        # Calls MetricReader#shutdown for all registered MetricReaders.
+        # Calls MetricExporter#shutdown for all registered MetricExporters.
+        #
+        # After this is called all the newly created {Meter}s will be no-op.
+        #
+        # @param [optional Numeric] timeout An optional timeout in seconds.
+        # @return [Integer] Export::SUCCESS if no error occurred, Export::FAILURE if
+        #   a non-specific failure occurred, Export::TIMEOUT if a timeout occurred.
+        def shutdown(timeout: nil)
+          @mutex.synchronize do
+            if @stopped
+              OpenTelemetry.logger.warn('calling MetricProvider#shutdown multiple times.')
+              Export::FAILURE
+            else
+              start_time = OpenTelemetry::Common::Utilities.timeout_timestamp
+
+              results = @metric_readers.map do |metric_reader|
+                remaining_timeout = OpenTelemetry::Common::Utilities.maybe_timeout(timeout, start_time)
+                break [Export::TIMEOUT] if remaining_timeout&.zero?
+                metric_reader.shutdown(timeout: remaining_timeout)
+              end
+
+              @stopped = true
+              results.max || Export::SUCCESS
+            end
+          end
+        end
+
+        # This method provides a way for provider to notify the registered
+        # {MetricReader} instances, so they can do as much as they could to consume
+        # or send the metrics. Note: unlike Push Metric Exporter which can send data on
+        # its own schedule, Pull Metric Exporter can only send the data when it is
+        # being asked by the scraper, so ForceFlush would not make much sense.
+        #
+        # @param [optional Numeric] timeout An optional timeout in seconds.
+        # @return [Integer] Export::SUCCESS if no error occurred, Export::FAILURE if
+        #   a non-specific failure occurred, Export::TIMEOUT if a timeout occurred.
+        def force_flush(timeout: nil)
+          @mutex.synchronize do
+            return Export::SUCCESS if @stopped
+
+            start_time = OpenTelemetry::Common::Utilities.timeout_timestamp
+            results = @metric_readers.map do |metric_reader|
+              remaining_timeout = OpenTelemetry::Common::Utilities.maybe_timeout(timeout, start_time)
+              return Export::TIMEOUT if remaining_timeout&.zero?
+
+              metric_reader.force_flush(timeout: remaining_timeout)
+            end
+            results.max || Export::SUCCESS
+          end
+        end
+
+        # Adds a new MetricReader to this {MeterProvider}.
+        #
+        # @param metric_reader the new MetricReader to be added.
+        def add_metric_reader(metric_reader)
+          @mutex.synchronize do
+            if @stopped
+              OpenTelemetry.logger.warn('calling MetricProvider#add_metric_reader after shutdown.')
+              return
+            end
+
+            @metric_readers = @metric_readers.push(metric_reader)
+          end
+        end
+
+        # The type of the Instrument(s) (optional).
+        # The name of the Instrument(s). OpenTelemetry SDK authors MAY choose to support wildcard characters, with the question mark (?) matching exactly one character and the asterisk character (*) matching zero or more characters.
+        # The name of the Meter (optional).
+        # The version of the Meter (optional).
+        # The schema_url of the Meter (optional).
+        def add_view
+          # TODO: For each meter add this view to all applicable instruments
         end
       end
     end

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

@@ -0,0 +1,114 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'test_helper'
+
+describe OpenTelemetry::SDK::Metrics::MeterProvider do
+  before do
+    reset_metrics_sdk
+    OpenTelemetry::SDK.configure
+  end
+
+  describe '#meter' do
+    it 'requires a meter name' do
+      _(-> { OpenTelemetry.meter_provider.meter }).must_raise(ArgumentError)
+    end
+
+    it 'creates a new meter' do
+      meter = OpenTelemetry.meter_provider.meter('test')
+
+      _(meter).must_be_instance_of(OpenTelemetry::SDK::Metrics::Meter)
+    end
+
+    it 'repeated calls does not recreate a meter of the same name' do
+      meter_a = OpenTelemetry.meter_provider.meter('test')
+      meter_b = OpenTelemetry.meter_provider.meter('test')
+
+      _(meter_a).must_equal(meter_b)
+    end
+  end
+
+  describe '#shutdown' do
+    it 'repeated calls to shutdown result in a failure' do
+      with_test_logger do |log_stream|
+        _(OpenTelemetry.meter_provider.shutdown).must_equal(OpenTelemetry::SDK::Metrics::Export::SUCCESS)
+        _(OpenTelemetry.meter_provider.shutdown).must_equal(OpenTelemetry::SDK::Metrics::Export::FAILURE)
+        _(log_stream.string).must_match(/calling MetricProvider#shutdown multiple times/)
+      end
+    end
+
+    it 'returns a no-op meter after being shutdown' do
+      with_test_logger do |log_stream|
+        OpenTelemetry.meter_provider.shutdown
+
+        _(OpenTelemetry.meter_provider.meter('test')).must_be_instance_of(OpenTelemetry::Metrics::Meter)
+        _(log_stream.string).must_match(/calling MeterProvider#meter after shutdown, a noop meter will be returned/)
+      end
+    end
+
+    it 'returns a timeout response when it times out' do
+      mock_metric_reader = Minitest::Mock.new
+      mock_metric_reader.expect(:nothing_gets_called_because_it_times_out_first, nil)
+      OpenTelemetry.meter_provider.add_metric_reader(mock_metric_reader)
+
+      _(OpenTelemetry.meter_provider.shutdown(timeout: 0)).must_equal(OpenTelemetry::SDK::Metrics::Export::TIMEOUT)
+    end
+
+    it 'invokes shutdown on all registered Metric Readers' do
+      mock_metric_reader_1 = Minitest::Mock.new
+      mock_metric_reader_2 = Minitest::Mock.new
+      mock_metric_reader_1.expect(:shutdown, nil, [{ timeout: nil }])
+      mock_metric_reader_2.expect(:shutdown, nil, [{ timeout: nil }])
+
+      OpenTelemetry.meter_provider.add_metric_reader(mock_metric_reader_1)
+      OpenTelemetry.meter_provider.add_metric_reader(mock_metric_reader_2)
+      OpenTelemetry.meter_provider.shutdown
+
+      mock_metric_reader_1.verify
+      mock_metric_reader_2.verify
+    end
+  end
+
+  describe '#force_flush' do
+    it 'returns a timeout response when it times out' do
+      mock_metric_reader = Minitest::Mock.new
+      mock_metric_reader.expect(:nothing_gets_called_because_it_times_out_first, nil)
+      OpenTelemetry.meter_provider.add_metric_reader(mock_metric_reader)
+
+      _(OpenTelemetry.meter_provider.force_flush(timeout: 0)).must_equal(OpenTelemetry::SDK::Metrics::Export::TIMEOUT)
+    end
+
+    it 'invokes force_flush on all registered Metric Readers' do
+      mock_metric_reader_1 = Minitest::Mock.new
+      mock_metric_reader_2 = Minitest::Mock.new
+      mock_metric_reader_1.expect(:force_flush, nil, [{ timeout: nil }])
+      mock_metric_reader_2.expect(:force_flush, nil, [{ timeout: nil }])
+      OpenTelemetry.meter_provider.add_metric_reader(mock_metric_reader_1)
+      OpenTelemetry.meter_provider.add_metric_reader(mock_metric_reader_2)
+
+      OpenTelemetry.meter_provider.force_flush
+
+      mock_metric_reader_1.verify
+      mock_metric_reader_2.verify
+    end
+  end
+
+  describe '#add_metric_reader' do
+    it 'adds a metric reader' do
+      metric_reader = OpenTelemetry::SDK::Metrics::Export::MetricReader.new(
+        OpenTelemetry::SDK::Metrics::Export::ConsoleExporter.new
+      )
+
+      OpenTelemetry.meter_provider.add_metric_reader(metric_reader)
+
+      _(OpenTelemetry.meter_provider.instance_variable_get(:@metric_readers)).must_equal([metric_reader])
+    end
+  end
+
+  describe '#add_view' do
+    # TODO
+  end
+end

metrics_sdk/test/test_helper.rb

@@ -23,3 +23,12 @@ def reset_metrics_sdk
   OpenTelemetry.logger = Logger.new(File::NULL)
   OpenTelemetry.error_handler = nil
 end
+
+def with_test_logger
+  log_stream = StringIO.new
+  original_logger = OpenTelemetry.logger
+  OpenTelemetry.logger = ::Logger.new(log_stream)
+  yield log_stream
+ensure
+  OpenTelemetry.logger = original_logger
+end