Add faraday instrumentation adapter #67

adapters/faraday/Gemfile

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+source 'https://rubygems.org'
+
+gemspec
+
+gem 'opentelemetry-api', path: '../../api'

adapters/faraday/example/Gemfile

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+gem 'faraday'
+gem 'opentelemetry-api', path: '../../../api'
+gem 'opentelemetry-sdk', path: '../../../sdk'

adapters/faraday/example/faraday.rb

@@ -0,0 +1,21 @@
+require 'rubygems'
+require 'bundler/setup'
+
+require 'faraday'
+require 'opentelemetry/sdk'
+require_relative '../lib/opentelemetry/adapters/faraday'
+
+# Set preferred tracer implementation:
+SDK = OpenTelemetry::SDK
+
+factory = OpenTelemetry.tracer_factory = SDK::Trace::TracerFactory.new
+factory.add_span_processor(
+  SDK::Trace::Export::SimpleSpanProcessor.new(
+    SDK::Trace::Export::ConsoleSpanExporter.new
+  )
+)
+
+OpenTelemetry::Adapters::Faraday.install(name: 'faraday-example', version: '1.0')
+
+conn = Faraday.new('http://example.com')
+conn.get '/'

adapters/faraday/lib/opentelemetry/adapters.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  # "Instrumentation adapters" are specified by
+  # https://github.com/open-telemetry/opentelemetry-specification/blob/57714f7547fe4dcb342ad0ad10a80d86118431c7/specification/overview.md#instrumentation-adapters
+  #
+  # Adapters should be able to handle the case when the library is not installed on a user's system.
+  module Adapters
+  end
+end

adapters/faraday/lib/opentelemetry/adapters/faraday.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Adapters
+    module Faraday
+      module_function
+
+      TRACER_NAME = 'faraday'
+      TRACER_VERSION = Gem.loaded_specs[TRACER_NAME]&.version.to_s
+
+      def install(config = {name: TRACER_NAME, version: TRACER_VERSION})
+        require_relative 'faraday/adapter'
+        Faraday::Adapter.install(config)
+      end
+    end
+  end
+end

adapters/faraday/lib/opentelemetry/adapters/faraday/adapter.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# TODO: General Question: should adapters explicitly load the libraries they depend on?
+# Or, should adapters assume that the libraries are already loaded by the caller/user?
+require 'faraday'
+require 'opentelemetry/adapter'
+
+require_relative 'middlewares/tracer_middleware'
+require_relative 'patches/rack_builder'
+
+module OpenTelemetry
+  module Adapters
+    module Faraday
+      class Adapter < OpenTelemetry::Adapter
+        def install
+          register_tracer_middleware
+          use_middleware_by_default
+        end
+
+        private
+
+        def register_tracer_middleware
+          ::Faraday::Middleware.register_middleware(
+            open_telemetry: Middlewares::TracerMiddleware
+          )
+        end
+
+        def use_middleware_by_default
+          ::Faraday::RackBuilder.prepend(Patches::RackBuilder)
+        end
+      end
+    end
+  end
+end

adapters/faraday/lib/opentelemetry/adapters/faraday/middlewares/tracer_middleware.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Adapters
+    module Faraday
+      module Middlewares
+        class TracerMiddleware < ::Faraday::Middleware
+          def call(env)
+            tracer.in_span(env.url.to_s,
+                          attributes: { 'component' => 'http',
+                                        'http.method' => env.method,
+                                        'http.url' => env.url.to_s },
+                          kind: :client) do |span|
+              propagate_context(span, env)
+
+              app.call(env).on_complete { |resp| trace_response(span, resp) }
+            end
+          end
+
+          private
+
+          attr_reader :app
+
+          def propagate_context(span, env)
+            formatter.extract(env)
+            formatter.inject(span.context, env.request_headers)
+          end
+
+          def formatter
+            Faraday::Adapter.http_formatter
+          end
+
+          def tracer
+            Faraday::Adapter.tracer
+          end
+
+          def trace_response(span, response)
+            span.set_attribute('http.status_code', response.status)
+            span.set_attribute('http.status_text', response.reason_phrase)
+          end
+        end
+      end
+    end
+  end
+end

adapters/faraday/lib/opentelemetry/adapters/faraday/patches/rack_builder.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+require_relative '../middlewares/tracer_middleware'
+
+module OpenTelemetry
+  module Adapters
+    module Faraday
+      module Patches
+        # Module to be prepended to force Faraday to use the middleware by
+        # default so the user doesn't have to call `use` for every connection.
+        module RackBuilder
+          def adapter(*args)
+            use(:open_telemetry) unless @handlers.any? do |handler|
+              handler.klass == Middlewares::TracerMiddleware
+            end
+
+            super
+          end
+        end
+      end
+    end
+  end
+end

adapters/faraday/lib/opentelemetry/adapters/faraday/version.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Adapters
+    module Faraday
+      VERSION = '0.0.0'
+    end
+  end
+end

adapters/faraday/opentelemetry-adapters-faraday.gemspec

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+lib = File.expand_path('lib', __dir__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+require 'opentelemetry/adapters/faraday/version'
+
+Gem::Specification.new do |spec|
+  spec.name        = 'opentelemetry-adapters-faraday'
+  spec.version     = OpenTelemetry::Adapters::Faraday::VERSION
+  spec.authors     = ['OpenTelemetry Authors']
+  spec.email       = ['[email protected]']
+
+  spec.summary     = 'Faraday instrumentation adapter for the OpenTelemetry framework'
+  spec.description = 'Faraday instrumentation adapter for the OpenTelemetry framework'
+  spec.homepage    = 'https://github.com/open-telemetry/opentelemetry-ruby'
+  spec.license     = 'Apache-2.0'
+
+  spec.files = ::Dir.glob('lib/**/*.rb') +
+               ::Dir.glob('*.md') +
+               ['LICENSE']
+  spec.require_paths = ['lib']
+  spec.required_ruby_version = '>= 2.4.0'
+
+  spec.add_dependency 'opentelemetry-api', '~> 0.0'
+
+  spec.add_development_dependency 'bundler', '>= 1.17'
+  spec.add_development_dependency 'faraday', '~> 0.17.0'
+end

api/lib/opentelemetry.rb

@@ -6,6 +6,7 @@
 require 'logger'
 
 require 'opentelemetry/error'
+require 'opentelemetry/adapter'
 require 'opentelemetry/context'
 require 'opentelemetry/distributed_context'
 require 'opentelemetry/internal'

api/lib/opentelemetry/adapter.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+# Copyright 2019 OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  # The basic interface for Adapter objects
+  class Adapter
+    class << self
+      attr_reader :config
+
+      def install(config = {})
+        @config = config
+        new.install
+      end
+
+      def http_formatter
+        OpenTelemetry.tracer_factory.http_text_format
+      end
+
+      def tracer
+        OpenTelemetry.tracer_factory.tracer(config[:name], config[:version])
+      end
+    end
+  end
+end

docker-compose.yml

@@ -24,6 +24,10 @@ services:
       context: .
     working_dir: /app
 
+  ex-adapter-faraday:
+    <<: *base
+    working_dir: /app/adapters/faraday/example
+
   sdk:
     <<: *base
     working_dir: /app/sdk

sdk/lib/opentelemetry/sdk/trace/tracer_factory.rb

@@ -8,7 +8,7 @@ module OpenTelemetry
   module SDK
     module Trace
       # {TracerFactory} is the SDK implementation of {OpenTelemetry::Trace::TracerFactory}.
-      class TracerFactory
+      class TracerFactory < OpenTelemetry::Trace::TracerFactory
         Key = Struct.new(:name, :version)
         private_constant(:Key)
 

sdk/test/opentelemetry/sdk/trace/export/batch_span_processor_test.rb

@@ -221,15 +221,15 @@ def to_span_data
     end
 
     describe 'normally' do
-      let(:exporter_sleeps_for_millis) { exporter_timeout_millis - 1 }
+      let(:exporter_sleeps_for_millis) { exporter_timeout_millis - 10 }
 
       it 'exporter is not interrupted' do
         _(exporter.state).must_equal(:not_interrupted)
       end
     end
 
     describe 'when exporter runs too long' do
-      let(:exporter_sleeps_for_millis) { exporter_timeout_millis + 1 }
+      let(:exporter_sleeps_for_millis) { exporter_timeout_millis + 10 }
 
       it 'is interrupted by a timeout' do
         _(exporter.state).must_equal(:called)