[sinatra] change the name with service_name instead of default_service (

#260)

docs/GettingStarted.md

@@ -142,7 +142,7 @@ either ``sinatra`` or ``sinatra/base``:
     require 'ddtrace/contrib/sinatra/tracer'
 
     Datadog.configure do |c|
-      c.use :sinatra, default_service: 'my-app'
+      c.use :sinatra, service_name: 'my-app'
     end
 
     get '/' do
@@ -157,7 +157,7 @@ Available settings are:
 
 * ``enabled``: define if the ``tracer`` is enabled or not. If set to ``false``, the code is still instrumented
   but no spans are sent to the local trace agent.
-* ``default_service``: set the service name used when tracing application requests. Defaults to ``sinatra``
+* ``service_name``: set the service name used when tracing application requests. Defaults to ``sinatra``
 * ``tracer``: set the tracer to use. Usually you don't need to change that value
   unless you're already using a different initialized tracer somewhere else
 * ``debug``: set to ``true`` to enable debug logging.

lib/ddtrace/contrib/sinatra/tracer.rb

@@ -27,7 +27,7 @@ module Tracer
           get_option(:tracer).enabled = value
         end
 
-        option :default_service, default: 'sinatra', depends_on: [:tracer] do |value|
+        option :service_name, default: 'sinatra', depends_on: [:tracer] do |value|
           get_option(:tracer).set_service_info(value, 'sinatra', Ext::AppTypes::WEB)
           value
         end
@@ -90,7 +90,7 @@ def render(engine, data, *)
             tracer = Datadog.configuration[:sinatra][:tracer]
 
             span = tracer.trace('sinatra.request',
-                                service: Datadog.configuration[:sinatra][:default_service],
+                                service: Datadog.configuration[:sinatra][:service_name],
                                 span_type: Datadog::Ext::HTTP::TYPE)
             span.set_tag(Datadog::Ext::HTTP::URL, request.path)
             span.set_tag(Datadog::Ext::HTTP::METHOD, request.request_method)

test/contrib/sinatra/tracer_test.rb

@@ -1,5 +1,6 @@
 require 'contrib/sinatra/tracer_test_base'
 
+# rubocop:disable Metrics/ClassLength
 class TracerTest < TracerTestBase
   class TracerTestApp < Sinatra::Application
     get '/request' do
@@ -45,6 +46,22 @@ def setup
     super
   end
 
+  def test_service_name
+    previous_name = Datadog.configuration[:sinatra][:service_name]
+    Datadog.configuration.use(:sinatra, service_name: 'my-sinatra-app')
+
+    get '/request'
+    assert_equal(200, last_response.status)
+
+    spans = @writer.spans()
+    assert_equal(1, spans.length)
+
+    span = spans[0]
+    assert_equal('my-sinatra-app', span.service)
+  ensure
+    Datadog.configuration.use(:sinatra, service_name: previous_name)
+  end
+
   def test_request
     get '/request#foo?a=1'
     assert_equal(200, last_response.status)