feat: Implement Logs Bridge API

This provides an interface for:
* LoggerProvider
* Logger
* LogRecord

This API will be consumed by the forthcoming Logs SDK.
Follows specification v 1.23.0.

.github/workflows/ci.yml

@@ -17,6 +17,7 @@ jobs:
         gem:
           - opentelemetry-api
           - opentelemetry-common
+          - opentelemetry-logs-api
           - opentelemetry-metrics-api
           - opentelemetry-registry
           - opentelemetry-sdk

logs_api/lib/opentelemetry/logs.rb

@@ -4,10 +4,21 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-require 'opentelemetry'
+require_relative 'logs/log_record'
+require_relative 'logs/logger_provider'
+require_relative 'logs/logger'
 
 module OpenTelemetry
-  # OpenTelemetry Logs API
+  # The Logs API records a timestamped text record with metadata.
+  # In OpenTelemetry, any data that is not part of a distributed trace or a
+  # metric is a log. For example, events are a specific type of log.
   module Logs
+    extend self
+
+    # Sets a global {LoggerProvider}
+    # @api public
+    def logger_provider
+      @logger_provider ||= LoggerProvider.new
+    end
   end
 end

logs_api/lib/opentelemetry/logs/log_record.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Logs
+    # No-op implementation of an emitted log and its associated attributes
+    class LogRecord; end
+  end
+end

logs_api/lib/opentelemetry/logs/logger.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Logs
+    # No-op implementation of logger.
+    class Logger
+      # Create a {LogRecord}
+      #
+      # @param timestamp [optional Float] Time when the event occurred measured
+      #   by the origin clock, i.e. the time at the source.
+      # @param observed_timestamp [optional Float] Time when the event was
+      #   observed by the collection system.
+      # @param context [optional Context] The Context to associate with the
+      #   LogRecord.
+      # @param severity_number [optional Integer] Numerical value of the
+      #   severity. Smaller numerical values correspond to less severe events
+      #   (such as debug events), larger numerical values correspond to more
+      #   severe events (such as errors and critical events).
+      # @param severity_text [optional String] Original string representation of
+      #   the severity as it is known at the source. Also known as log level.
+      # @param body [optional String, Numeric, Boolean, Array<String, Numeric,
+      #   Boolean>, Hash{String => String, Numeric, Boolean, Array<String,
+      #   Numeric, Boolean>}] A value containing the body of the log record.
+      # @param attributes [optional Hash{String => String, Numeric, Boolean,
+      #   Array<String, Numeric, Boolean>}] Additional information about the
+      #   event.
+      #
+      # @api public
+      def create_log_record(
+        timestamp: nil,
+        observed_timestamp: nil,
+        context: nil,
+        severity_number: nil,
+        severity_text: nil,
+        body: nil,
+        attributes: nil
+      )
+        LogRecord.new
+      end
+    end
+  end
+end

logs_api/lib/opentelemetry/logs/logger_provider.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Logs
+    # No-op implementation of a logger provider
+    class LoggerProvider
+      # Returns a {Logger} instance.
+      #
+      # @param name [optional String] Instrumentation package name
+      # @param version [optional String] Instrumentation package version
+      # @param schema_url [optional String] Schema URL recorded in the emitted telemetry.
+      # @param attributes [optional Hash] Specifies the instrumentation scope
+      #  attributes to associate with emitted telemetry.
+      #
+      # @return [OpenTelemetry::Logs::Logger]
+      #
+      # @api public
+      def logger(name: nil, version: nil, schema_url: nil, attributes: {})
+        @logger ||= OpenTelemetry::Logs::Logger.new
+      end
+    end
+  end
+end

logs_api/opentelemetry-logs-api.gemspec

@@ -24,8 +24,6 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
   spec.required_ruby_version = '>= 3.0'
 
-  spec.add_dependency 'opentelemetry-api', '~> 1.0'
-
   spec.add_development_dependency 'bundler', '>= 1.17'
   spec.add_development_dependency 'minitest', '~> 5.0'
   spec.add_development_dependency 'rake', '~> 12.0'

logs_api/test/.rubocop.yml

@@ -0,0 +1,8 @@
+inherit_from: ../.rubocop.yml
+
+Metrics/BlockLength:
+  Enabled: false
+Metrics/LineLength:
+  Enabled: false
+Metrics/AbcSize:
+  Enabled: false

logs_api/test/opentelemetry/logs/logger_provider_test.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'test_helper'
+
+describe OpenTelemetry::Logs::LoggerProvider do
+  let(:logger_provider) { OpenTelemetry::Logs.logger_provider }
+
+  describe '#logger' do
+    it 'returns the same logger for the same arguments' do
+      logger1 = logger_provider.logger(
+        name: 'component',
+        version: '1.0',
+        schema_url: 'example.com',
+        attributes: { a: 1 }
+      )
+
+      logger2 = logger_provider.logger(
+        name: 'component',
+        version: '1.0',
+        schema_url: 'example.com',
+        attributes: { a: 1 }
+      )
+      assert_same(logger1, logger2)
+    end
+  end
+end

logs_api/test/opentelemetry/logs/logger_test.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'test_helper'
+
+describe OpenTelemetry::Logs::Logger do
+  let(:logger) { OpenTelemetry::Logs::Logger.new }
+
+  describe '#create_log_record' do
+    it 'creates a new LogRecord' do
+      assert_instance_of(OpenTelemetry::Logs::LogRecord, logger.create_log_record)
+    end
+  end
+end

logs_api/test/opentelemetry/logs_test.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'test_helper'
+
+describe OpenTelemetry::Logs do
+  describe '#logger_provider' do
+    it 'returns an instance of LoggerProvider' do
+      assert_equal(OpenTelemetry::Logs::LoggerProvider, OpenTelemetry::Logs.logger_provider.class)
+    end
+
+    it 'always uses the same LoggerProvider' do
+      first_call = OpenTelemetry::Logs.logger_provider
+      second_call = OpenTelemetry::Logs.logger_provider
+      assert_same(first_call, second_call)
+    end
+  end
+end

logs_api/test/test_helper.rb

@@ -5,12 +5,8 @@
 # SPDX-License-Identifier: Apache-2.0
 
 require 'simplecov'
-SimpleCov.start
+SimpleCov.start { enable_coverage :branch }
 SimpleCov.minimum_coverage 85
 
-require 'opentelemetry-test-helpers'
-require 'opentelemetry-metrics-api'
+require 'opentelemetry-logs-api'
 require 'minitest/autorun'
-require 'pry'
-
-OpenTelemetry.logger = Logger.new(File::NULL)