feat: add experimental otlp metrics exporter

exporter/otlp-metrics/.rubocop.yml

@@ -0,0 +1,42 @@
+AllCops:
+  TargetRubyVersion: "3.0"
+  NewCops: disable
+  SuggestExtensions: false
+  Exclude:
+    - "lib/opentelemetry/proto/**/*"
+    - "vendor/**/*"
+
+Bundler/OrderedGems:
+  Exclude:
+    - gemfiles/**/*
+Lint/UnusedMethodArgument:
+  Enabled: false
+Lint/MissingSuper:
+  Enabled: false
+Lint/ConstantDefinitionInBlock:
+  Exclude:
+    - "test/**/*"
+Style/StringConcatenation:
+  Exclude:
+    - "test/**/*"
+Metrics/AbcSize:
+  Enabled: false
+Layout/LineLength:
+  Enabled: false
+Metrics/MethodLength:
+  Max: 20
+Metrics/ParameterLists:
+  Enabled: false
+Style/FrozenStringLiteralComment:
+  Exclude:
+    - gemfiles/**/*
+Style/ModuleFunction:
+  Enabled: false
+Style/StringLiterals:
+  Exclude:
+    - gemfiles/**/*
+Metrics/BlockLength:
+  Enabled: false
+Naming/FileName:
+  Exclude:
+    - "lib/opentelemetry-exporter-otlp-metrics.rb"

exporter/otlp-metrics/.yardopts

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+--no-private
+--title=OpenTelemetry OTLP Metrics Exporter
+--markup=markdown
+--main=README.md
+./lib/opentelemetry/exporter/otlp/**/*.rb
+./lib/opentelemetry/exporter/otlp.rb
+-
+README.md
+CHANGELOG.md

exporter/otlp-metrics/Appraisals

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+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+(14..23).each do |i|
+  version = "3.#{i}"
+  appraise "google-protobuf-#{version}" do
+    gem 'google-protobuf', "~> #{version}"
+  end
+end

exporter/otlp-metrics/CHANGELOG.md

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+# Release History: opentelemetry-exporter-otlp-metrics
+
+### v0.0.1 / 2023-12-07
+
+* Initial release.

exporter/otlp-metrics/Gemfile

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+source 'https://rubygems.org'
+
+gemspec
+
+group :test, :development do
+  gem 'opentelemetry-api', path: '../../api'
+  gem 'opentelemetry-common', path: '../../common'
+  gem 'opentelemetry-metrics-api', path: '../../metrics_api'
+  gem 'opentelemetry-metrics-sdk', path: '../../metrics_sdk'
+  gem 'opentelemetry-registry', path: '../../registry'
+  gem 'opentelemetry-sdk', path: '../../sdk'
+  gem 'opentelemetry-semantic_conventions', path: '../../semantic_conventions'
+  gem 'opentelemetry-test-helpers', path: '../../test_helpers'
+end

exporter/otlp-metrics/LICENSE

@@ -0,0 +1,201 @@
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