Fix adapter examples and simplify setup

adapters/faraday/example/Gemfile

@@ -5,3 +5,4 @@ source 'https://rubygems.org'
 gem 'faraday'
 gem 'opentelemetry-api', path: '../../../api'
 gem 'opentelemetry-sdk', path: '../../../sdk'
+gem 'opentelemetry-adapters-faraday', path: '../../../adapters/faraday'

adapters/faraday/example/faraday.rb

@@ -1,19 +1,11 @@
 require 'rubygems'
 require 'bundler/setup'
 
-require 'faraday'
-require 'opentelemetry/sdk'
-require_relative '../lib/opentelemetry/adapters/faraday'
+Bundler.require
 
-# 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::SDK.configure do |c|
+  c.use 'OpenTelemetry::Adapters::Faraday'
+end
 
 # Demonstrate disabling span reporting:
 #
@@ -25,7 +17,5 @@
 # end
 # OpenTelemetry::Adapters::Faraday.install(tracer_middleware: NoOp)
 
-OpenTelemetry::Adapters::Faraday.install
-
 conn = Faraday.new('http://example.com')
 conn.get '/'

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

@@ -16,7 +16,7 @@ class Adapter < OpenTelemetry::Instrumentation::Adapter
         end
 
         present do
-          Gem.loaded_specs.include?('faraday')
+          defined?(::Faraday)
         end
 
         private

adapters/faraday/test/test_helper.rb

@@ -12,11 +12,9 @@
 require 'webmock/minitest'
 
 # global opentelemetry-sdk setup:
-sdk = OpenTelemetry::SDK
-exporter = sdk::Trace::Export::InMemorySpanExporter.new
-span_processor = sdk::Trace::Export::SimpleSpanProcessor.new(exporter)
-OpenTelemetry.tracer_factory = sdk::Trace::TracerFactory.new.tap do |factory|
-  factory.add_span_processor(span_processor)
-end
+EXPORTER = OpenTelemetry::SDK::Trace::Export::InMemorySpanExporter.new
+span_processor = OpenTelemetry::SDK::Trace::Export::SimpleSpanProcessor.new(EXPORTER)
 
-EXPORTER = exporter
+OpenTelemetry::SDK.configure do |c|
+  c.add_span_processor span_processor
+end

adapters/sinatra/example/Gemfile

@@ -5,3 +5,4 @@ source 'https://rubygems.org'
 gem 'sinatra'
 gem 'opentelemetry-api', path: '../../../api'
 gem 'opentelemetry-sdk', path: '../../../sdk'
+gem 'opentelemetry-adapters-sinatra', path: '../../../adapters/sinatra'

adapters/sinatra/example/server.rb

@@ -2,21 +2,11 @@
 require 'rubygems'
 require 'bundler/setup'
 
-require 'sinatra/base'
-require 'opentelemetry/sdk'
-require_relative '../lib/opentelemetry/adapters/sinatra'
+Bundler.require
 
-# 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::Sinatra.install
+OpenTelemetry::SDK.configure do |c|
+  c.use 'OpenTelemetry::Adapters::Sinatra'
+end
 
 class App < Sinatra::Base
   set :bind, '0.0.0.0'

adapters/sinatra/lib/opentelemetry/adapters/sinatra/adapter.rb

@@ -15,7 +15,7 @@ class Adapter < OpenTelemetry::Instrumentation::Adapter
         end
 
         present do
-          Gem.loaded_specs.include?("sinatra")
+          defined?(::Sinatra)
         end
       end
     end

adapters/sinatra/test/test_helper.rb

@@ -12,11 +12,9 @@
 require 'rack/test'
 
 # global opentelemetry-sdk setup:
-sdk = OpenTelemetry::SDK
-exporter = sdk::Trace::Export::InMemorySpanExporter.new
-span_processor = sdk::Trace::Export::SimpleSpanProcessor.new(exporter)
-OpenTelemetry.tracer_factory = sdk::Trace::TracerFactory.new.tap do |factory|
-  factory.add_span_processor(span_processor)
-end
+EXPORTER = OpenTelemetry::SDK::Trace::Export::InMemorySpanExporter.new
+span_processor = OpenTelemetry::SDK::Trace::Export::SimpleSpanProcessor.new(EXPORTER)
 
-EXPORTER = exporter
+OpenTelemetry::SDK.configure do |c|
+  c.add_span_processor span_processor
+end

api/lib/opentelemetry/instrumentation/adapter.rb

@@ -27,7 +27,7 @@ module Instrumentation
     #
     #         # determine if the target library is present
     #         present do
-    #           Gem.loaded_specs.key?('sinatra')
+    #           defined?(::Sinatra)
     #         end
     #
     #         # if the target library is present, is it compatible?