feat(otel): add support for otel metrics

.env

@@ -3,6 +3,8 @@ DD_AGENT_HOST=testagent
 DD_API_KEY=00000000000000000000000000000000
 DD_METRIC_AGENT_PORT=8125
 DD_TRACE_AGENT_PORT=9126
+OTLP_HTTP_PORT=4318
+OTLP_GRPC_PORT=4317
 
 # Values are used for proxying from APM Test Agent to real Datadog Agent
 DD_REAL_AGENT_HOST=ddagent

.github/workflows/_unit_test.yml

@@ -131,6 +131,8 @@ jobs:
         TEST_MYSQL_HOST: mysql
         DD_AGENT_HOST: agent
         DD_TRACE_AGENT_PORT: '9126'
+        OTLP_GRPC_PORT: '4317'
+        OTLP_HTTP_PORT: '4318'
         DATADOG_GEM_CI: 'true'
         TEST_DATADOG_INTEGRATION: '1'
         JRUBY_OPTS: "--dev" # Faster JVM startup: https://github.com/jruby/jruby/wiki/Improving-startup-time#use-the---dev-flag
@@ -141,6 +143,8 @@ jobs:
           LOG_LEVEL: DEBUG
           TRACE_LANGUAGE: ruby
           PORT: '9126'
+          OTLP_GRPC_PORT: '4317'
+          OTLP_HTTP_PORT: '4318'
           DD_POOL_TRACE_CHECK_FAILURES: 'true'
           DD_DISABLE_ERROR_RESPONSES: 'true'
           ENABLED_CHECKS: trace_content_length,trace_stall,meta_tracer_version_header,trace_count_header,trace_peer_service,trace_dd_service
@@ -211,6 +215,8 @@ jobs:
           LOG_LEVEL: DEBUG
           TRACE_LANGUAGE: ruby
           PORT: '9126'
+          OTLP_GRPC_PORT: '4317'
+          OTLP_HTTP_PORT: '4318'
           DD_POOL_TRACE_CHECK_FAILURES: 'true'
           DD_DISABLE_ERROR_RESPONSES: 'true'
           ENABLED_CHECKS: trace_content_length,trace_stall,meta_tracer_version_header,trace_count_header,trace_peer_service,trace_dd_service

appraisal/ruby-3.1.rb

@@ -169,6 +169,8 @@
 
 appraise 'opentelemetry' do
   gem 'opentelemetry-sdk', '~> 1.1'
+  gem 'opentelemetry-metrics-sdk', '>= 0.8'
+  gem 'opentelemetry-exporter-otlp-metrics', '>= 0.4'
 end
 
 appraise 'opentelemetry_otlp' do

appraisal/ruby-3.2.rb

@@ -214,6 +214,8 @@
 
 appraise 'opentelemetry' do
   gem 'opentelemetry-sdk', '~> 1.1'
+  gem 'opentelemetry-metrics-sdk', '>= 0.8'
+  gem 'opentelemetry-exporter-otlp-metrics', '>= 0.4'
 end
 
 appraise 'opentelemetry_otlp' do

appraisal/ruby-3.3.rb

@@ -216,6 +216,8 @@
 
 appraise 'opentelemetry' do
   gem 'opentelemetry-sdk', '~> 1.1'
+  gem 'opentelemetry-metrics-sdk', '>= 0.8'
+  gem 'opentelemetry-exporter-otlp-metrics', '>= 0.4'
 end
 
 appraise 'opentelemetry_otlp' do

appraisal/ruby-3.4.rb

@@ -229,6 +229,8 @@
 
 appraise 'opentelemetry' do
   gem 'opentelemetry-sdk', '~> 1.1'
+  gem 'opentelemetry-metrics-sdk', '>= 0.8'
+  gem 'opentelemetry-exporter-otlp-metrics', '>= 0.4'
 end
 
 appraise 'opentelemetry_otlp' do

appraisal/ruby-4.0.rb

@@ -175,6 +175,10 @@
 
 appraise 'opentelemetry' do
   gem 'opentelemetry-sdk', '~> 1.1'
+  gem 'opentelemetry-metrics-sdk', '>= 0.8'
+  gem 'opentelemetry-exporter-otlp-metrics', '>= 0.4'
+  # opentelemetry-metrics-sdk 0.11+ requires opentelemetry-common >= 0.23.0 (for time_in_nanoseconds)
+  gem "opentelemetry-common", ">= 0.23.0"
 end
 
 appraise 'opentelemetry_otlp' do

docker-compose.yml

@@ -263,6 +263,8 @@ services:
     image: ghcr.io/datadog/dd-apm-test-agent/ddapm-test-agent:v1.37.0
     ports:
       - "127.0.0.1:${DD_TRACE_AGENT_PORT}:9126"
+      - "127.0.0.1:${OTLP_GRPC_PORT}:4317"
+      - "127.0.0.1:${OTLP_HTTP_PORT}:4318"
     depends_on:
       - ddagent
     env_file: ./.env
@@ -271,6 +273,8 @@ services:
       - TRACE_LANGUAGE=ruby
       - DD_TRACE_AGENT_URL=http://${DD_REAL_AGENT_HOST}:${DD_REAL_AGENT_PORT}
       - PORT=${DD_TRACE_AGENT_PORT}
+      - OTLP_GRPC_PORT=${OTLP_GRPC_PORT}
+      - OTLP_HTTP_PORT=${OTLP_HTTP_PORT}
       - DD_POOL_TRACE_CHECK_FAILURES=true
       - DD_DISABLE_ERROR_RESPONSES=true
       - ENABLED_CHECKS=trace_content_length,trace_stall,meta_tracer_version_header,trace_count_header,trace_peer_service,trace_dd_service

docs/OpenTelemetry.md

@@ -1,12 +1,14 @@
 # OpenTelemetry
 
-**Supported tracing frameworks**:
+**Supported OpenTelemetry features**:
 
 | Type          | Documentation                                        | datadog version | Gem version support |
 | ------------- | ---------------------------------------------------- | --------------- | ------------------- |
-| OpenTelemetry | https://github.com/open-telemetry/opentelemetry-ruby | 1.9.0+          | >= 1.1.0            |
+| Tracing       | https://github.com/open-telemetry/opentelemetry-ruby | 1.9.0+          | >= 1.1.0            |
+| Metrics SDK   | https://rubygems.org/gems/opentelemetry-metrics-sdk  | 2.23.0+         |  >= 0.8             |
+| OTLP Metrics Exporter | https://rubygems.org/gems/opentelemetry-exporter-otlp-metrics  | 2.23.0+         |  >= 0.4            |
 
-## Configuring OpenTelemetry
+## Configuring OpenTelemetry Tracing
 
 1. Add the `datadog` gem to your Gemfile:
 
@@ -44,6 +46,53 @@
 
    [Integration instrumentations](#integration-instrumentation) and OpenTelemetry [Automatic instrumentations](https://opentelemetry.io/docs/instrumentation/ruby/automatic/) are also supported.
 
+## Configuring OpenTelemetry Metrics
+
+1. Add the required gems to your Gemfile:
+
+    ```ruby
+    gem 'datadog'
+    gem 'opentelemetry-metrics-sdk', '~> 0.8'
+    gem 'opentelemetry-exporter-otlp-metrics', '~> 0.4'
+    ```
+
+1. Install gems with `bundle install`
+
+1. Enable metrics export:
+
+    ```ruby
+    # Set environment variable before initializing metrics support
+    ENV['DD_METRICS_OTEL_ENABLED'] = 'true'
+    require 'opentelemetry/sdk'
+    require 'datadog/opentelemetry'
+
+    Datadog.configure do |c|
+      # Configure Datadog settings here
+    end
+
+    # Call after Datadog.configure to initialize metrics.
+    # Can be called multiple times to pick up configuration changes.
+    # Requires: opentelemetry/exporter/otlp_metrics and opentelemetry/exporter/otlp_metrics
+    OpenTelemetry::SDK.configure
+    ```
+
+1. Use the [OpenTelemetry Metrics API](https://opentelemetry.io/docs/languages/ruby/instrumentation/#metrics) to create and record metrics.
+
+**Note:** Call `OpenTelemetry::SDK.configure` after `Datadog.configure` and call it again whenever Datadog configuration changes to update the meter provider.
+
+**Configuration Options:**
+
+- `DD_METRICS_OTEL_ENABLED` - Enable metrics export (default: false)
+- `OTEL_EXPORTER_OTLP_METRICS_PROTOCOL` - Protocol: `http/protobuf` (default); `grpc` and `http/json` are not yet supported.
+- `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT` - Custom endpoint (defaults to the Datadog agent otlp endpoint)
+- `OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE` - `delta` (default) or `cumulative`
+- `OTEL_METRIC_EXPORT_INTERVAL` - Export interval in milliseconds (default: 10000)
+
+[General OTLP settings](https://opentelemetry.io/docs/languages/sdk-configuration/otlp-exporter/) (`OTEL_EXPORTER_OTLP_*`) serve as defaults if metrics-specific settings are not provided.
+
+**Note:** Minimum `opentelemetry-metrics-sdk` is v0.8.0 (contains critical bug fixes). Minimum `opentelemetry-exporter-otlp-metrics` is v0.4.0. Use the latest versions for best support. If you spot any issue with the OpenTelemetry API affecting the `datadog` gem, [please do open a GitHub issue](https://github.com/DataDog/dd-trace-rb/issues).
+
+
 ## Limitations
 
 There are a few limitations to OpenTelemetry Tracing when the APM integration is activated: