feat: add basic periodic exporting metric_reader

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

@@ -26,3 +26,4 @@ module Export
 require 'opentelemetry/sdk/metrics/export/metric_reader'
 require 'opentelemetry/sdk/metrics/export/in_memory_metric_pull_exporter'
 require 'opentelemetry/sdk/metrics/export/console_metric_pull_exporter'
+require 'opentelemetry/sdk/metrics/export/periodic_metric_reader'

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

@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module SDK
+    module Metrics
+      module Export
+        # PeriodicMetricReader provides a minimal example implementation.
+        class PeriodicMetricReader < MetricReader
+          def initialize(interval_millis: 60, timout_millis: 30, exporter: nil)
+            super()
+
+            @interval_millis = interval_millis
+            @timout_millis = timout_millis
+            @exporter = exporter
+            @thread   = nil
+            @continue = false
+
+            start
+          end
+
+          def start
+            @continue = true
+            if @exporter.nil?
+              OpenTelemetry.logger.warn 'Missing exporter in PeriodicMetricReader.'
+            elsif @thread&.alive?
+              OpenTelemetry.logger.warn 'PeriodicMetricReader is still running. Please close it if it needs to restart.'
+            else
+              @thread = Thread.new do
+                while @continue
+                  sleep(@interval_millis)
+                  begin
+                    Timeout.timeout(@timout_millis) { @exporter.export(collect) }
+                  rescue Timeout::Error => e
+                    OpenTelemetry.handle_error(exception: e, message: 'PeriodicMetricReader timeout.')
+                  end
+                end
+              end
+            end
+          end
+
+          def close
+            @continue = false   # force termination in next iteration
+            @thread.join(5)     # wait 5 seconds for collecting and exporting
+          rescue StandardError => e
+            OpenTelemetry.handle_error(exception: e, message: 'Fail to close PeriodicMetricReader.')
+          end
+
+          # TODO: determine correctness: directly kill the reader without waiting for next metrics collection
+          def shutdown(timeout: nil)
+            close
+            @exporter.shutdown
+            Export::SUCCESS
+          rescue StandardError
+            Export::FAILURE
+          end
+
+          def force_flush(timeout: nil)
+            @exporter.export(collect)
+            Export::SUCCESS
+          rescue StandardError
+            Export::FAILURE
+          end
+        end
+      end
+    end
+  end
+end

metrics_sdk/test/integration/periodic_metric_reader_test.rb

@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'test_helper'
+
+describe OpenTelemetry::SDK do
+  describe '#periodic_metric_reader' do
+    before { reset_metrics_sdk }
+
+    it 'emits 2 metrics after 10 seconds' do
+      OpenTelemetry::SDK.configure
+
+      metric_exporter = OpenTelemetry::SDK::Metrics::Export::InMemoryMetricPullExporter.new
+      periodic_metric_reader = OpenTelemetry::SDK::Metrics::Export::PeriodicMetricReader.new(interval_millis: 5, timout_millis: 5, exporter: metric_exporter)
+
+      OpenTelemetry.meter_provider.add_metric_reader(periodic_metric_reader)
+
+      meter = OpenTelemetry.meter_provider.meter('test')
+      counter = meter.create_counter('counter', unit: 'smidgen', description: 'a small amount of something')
+
+      counter.add(1)
+      counter.add(2, attributes: { 'a' => 'b' })
+      counter.add(2, attributes: { 'a' => 'b' })
+      counter.add(3, attributes: { 'b' => 'c' })
+      counter.add(4, attributes: { 'd' => 'e' })
+
+      sleep(8)
+
+      periodic_metric_reader.shutdown
+      snapshot = metric_exporter.metric_snapshots
+
+      _(snapshot.size).must_equal(2)
+
+      first_snapshot = snapshot[0]
+      _(first_snapshot[0].name).must_equal('counter')
+      _(first_snapshot[0].unit).must_equal('smidgen')
+      _(first_snapshot[0].description).must_equal('a small amount of something')
+
+      _(first_snapshot[0].instrumentation_scope.name).must_equal('test')
+
+      _(first_snapshot[0].data_points[0].value).must_equal(1)
+      _(first_snapshot[0].data_points[0].attributes).must_equal({})
+
+      _(first_snapshot[0].data_points[1].value).must_equal(4)
+      _(first_snapshot[0].data_points[1].attributes).must_equal('a' => 'b')
+
+      _(first_snapshot[0].data_points[2].value).must_equal(3)
+      _(first_snapshot[0].data_points[2].attributes).must_equal('b' => 'c')
+
+      _(first_snapshot[0].data_points[3].value).must_equal(4)
+      _(first_snapshot[0].data_points[3].attributes).must_equal('d' => 'e')
+
+      puts periodic_metric_reader.instance_variable_get(:@thread)
+      _(periodic_metric_reader.instance_variable_get(:@thread).alive?).must_equal false
+    end
+
+    it 'emits 1 metrics after 1 seconds when interval is > 1 seconds' do
+      OpenTelemetry::SDK.configure
+
+      metric_exporter = OpenTelemetry::SDK::Metrics::Export::InMemoryMetricPullExporter.new
+      periodic_metric_reader = OpenTelemetry::SDK::Metrics::Export::PeriodicMetricReader.new(interval_millis: 5, timout_millis: 5, exporter: metric_exporter)
+
+      OpenTelemetry.meter_provider.add_metric_reader(periodic_metric_reader)
+
+      meter = OpenTelemetry.meter_provider.meter('test')
+      counter = meter.create_counter('counter', unit: 'smidgen', description: 'a small amount of something')
+
+      counter.add(1)
+      counter.add(2, attributes: { 'a' => 'b' })
+      counter.add(2, attributes: { 'a' => 'b' })
+      counter.add(3, attributes: { 'b' => 'c' })
+      counter.add(4, attributes: { 'd' => 'e' })
+
+      sleep(1)
+
+      periodic_metric_reader.shutdown
+      snapshot = metric_exporter.metric_snapshots
+
+      _(snapshot.size).must_equal(1)
+      _(periodic_metric_reader.instance_variable_get(:@thread).alive?).must_equal false
+    end
+  end
+end