Enable priority sampling by default

docs/GettingStarted.md

@@ -1356,15 +1356,7 @@ The sampler can set the priority to the following values:
  - `Datadog::Ext::Priority::AUTO_REJECT`: the sampler automatically decided to reject the trace.
  - `Datadog::Ext::Priority::AUTO_KEEP`: the sampler automatically decided to keep the trace.
 
-For now, priority sampling is disabled by default. Enabling it ensures that your sampled distributed traces will be complete. To enable the priority sampling:
-
-```ruby
-Datadog.configure do |c|
-  c.tracer priority_sampling: true
-end
-```
-
-Once enabled, the sampler will automatically assign a priority of 0 or 1 to traces, depending on their service and volume.
+Priority sampling is enabled by default. Enabling it ensures that your sampled distributed traces will be complete. Once enabled, the sampler will automatically assign a priority of 0 or 1 to traces, depending on their service and volume.
 
 You can also set this priority manually to either drop a non-interesting trace or to keep an important one. For that, set the `context#sampling_priority` to:
 

lib/ddtrace/tracer.rb

@@ -126,17 +126,23 @@ def configure(options = {})
 
       # Those are rare "power-user" options.
       sampler = options.fetch(:sampler, nil)
-      priority_sampling = options[:priority_sampling]
+      priority_sampling = options.fetch(:priority_sampling, nil)
       max_spans_before_partial_flush = options.fetch(:max_spans_before_partial_flush, nil)
       min_spans_before_partial_flush = options.fetch(:min_spans_before_partial_flush, nil)
       partial_flush_timeout = options.fetch(:partial_flush_timeout, nil)
 
       @enabled = enabled unless enabled.nil?
       @sampler = sampler unless sampler.nil?
 
-      if priority_sampling
+      # Re-build the sampler and writer if priority sampling is enabled,
+      # but neither are configured. Verify the sampler isn't already a
+      # priority sampler too, so we don't wrap one with another.
+      if priority_sampling != false && [email protected]_a?(PrioritySampler)
         @sampler = PrioritySampler.new(base_sampler: @sampler)
         @writer = Writer.new(priority_sampler: @sampler)
+      elsif priority_sampling == false
+        @sampler = sampler || Datadog::AllSampler.new if @sampler.is_a?(PrioritySampler)
+        @writer = Writer.new
       end
 
       @writer.transport.hostname = hostname unless hostname.nil?

spec/ddtrace/configuration/pin_setup_spec.rb

@@ -24,7 +24,7 @@
         }
       end
 
-      let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+      let(:tracer) { get_test_tracer }
 
       it do
         expect(target.datadog_pin.service).to eq('my-service')

spec/ddtrace/context_spec.rb

@@ -5,7 +5,7 @@
 RSpec.describe Datadog::Context do
   subject(:context) { described_class.new(options) }
   let(:options) { {} }
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   describe '#current_root_span' do
     subject(:current_root_span) { context.current_root_span }

spec/ddtrace/contrib/active_model_serializers/patcher_spec.rb

@@ -10,7 +10,7 @@
 RSpec.describe 'ActiveModelSerializers patcher' do
   include_context 'AMS serializer'
 
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   def all_spans
     tracer.writer.spans(:keep)

spec/ddtrace/contrib/active_record/multi_db_spec.rb

@@ -6,7 +6,7 @@
 require 'sqlite3'
 
 RSpec.describe 'ActiveRecord multi-database implementation' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:configuration_options) { { tracer: tracer, service_name: default_db_service_name } }
   let(:default_db_service_name) { 'default-db' }
 

spec/ddtrace/contrib/active_record/performance_spec.rb

@@ -5,7 +5,7 @@
 require 'sqlite3'
 
 RSpec.describe 'ActiveRecord tracing performance' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:options) { { tracer: tracer } }
   let(:spans) { tracer.writer.spans }
 

spec/ddtrace/contrib/active_record/tracer_spec.rb

@@ -4,7 +4,7 @@
 require_relative 'app'
 
 RSpec.describe 'ActiveRecord instrumentation' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:configuration_options) { { tracer: tracer } }
 
   before(:each) do

spec/ddtrace/contrib/active_support/notifications/subscription_spec.rb

@@ -7,7 +7,7 @@
 RSpec.describe Datadog::Contrib::ActiveSupport::Notifications::Subscription do
   describe 'instance' do
     subject(:subscription) { described_class.new(tracer, span_name, options, &block) }
-    let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+    let(:tracer) { get_test_tracer }
     let(:span_name) { double('span_name') }
     let(:options) { {} }
     let(:payload) { {} }

spec/ddtrace/contrib/aws/instrumentation_spec.rb

@@ -6,7 +6,7 @@
 require 'ddtrace/ext/http'
 
 RSpec.describe 'AWS instrumentation' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   let(:client) { ::Aws::S3::Client.new(stub_responses: responses) }
   let(:responses) { true }

spec/ddtrace/contrib/concurrent_ruby/integration_spec.rb

@@ -12,7 +12,7 @@
     remove_patch!(:concurrent_ruby)
   end
 
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:configuration_options) { { tracer: tracer } }
 
   subject(:deferred_execution) do

spec/ddtrace/contrib/dalli/instrumentation_spec.rb

@@ -9,7 +9,7 @@
   let(:test_port) { ENV.fetch('TEST_MEMCACHED_PORT', '11211') }
 
   let(:client) { ::Dalli::Client.new("#{test_host}:#{test_port}") }
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:pin) { ::Dalli.datadog_pin }
 
   def all_spans

spec/ddtrace/contrib/delayed_job/plugin_spec.rb

@@ -24,7 +24,7 @@ def job_data
     end)
   end
 
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   before do
     Datadog.configure { |c| c.use :delayed_job, tracer: tracer }

spec/ddtrace/contrib/elasticsearch/patcher_spec.rb

@@ -9,7 +9,7 @@
 
   let(:client) { Elasticsearch::Client.new(url: server) }
   let(:pin) { Datadog::Pin.get_from(client) }
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   before do
     Datadog.configure do |c|

spec/ddtrace/contrib/elasticsearch/transport_spec.rb

@@ -22,7 +22,7 @@
   let(:server) { "http://#{host}:#{port}" }
 
   let(:client) { Elasticsearch::Client.new(url: server) }
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   let(:spans) { tracer.writer.spans }
   let(:span) { spans.first }

spec/ddtrace/contrib/excon/instrumentation_spec.rb

@@ -5,7 +5,7 @@
 require 'ddtrace/contrib/excon/middleware'
 
 RSpec.describe Datadog::Contrib::Excon::Middleware do
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   let(:connection_options) { { mock: true } }
   let(:middleware_options) { {} }

spec/ddtrace/contrib/faraday/middleware_spec.rb

@@ -5,7 +5,7 @@
 require 'ddtrace/ext/distributed'
 
 RSpec.describe 'Faraday middleware' do
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   let(:client) do
     ::Faraday.new('http://example.com') do |builder|

spec/ddtrace/contrib/graphql/tracer_spec.rb

@@ -14,7 +14,7 @@
     end
   end
 
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   def pop_spans
     tracer.writer.spans(:keep)

spec/ddtrace/contrib/http/patcher_spec.rb

@@ -3,7 +3,7 @@
 require 'net/http'
 
 RSpec.describe 'net/http patcher' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:host) { 'example.com' }
 
   before do

spec/ddtrace/contrib/mongodb/client_spec.rb

@@ -4,7 +4,7 @@
 require 'mongo'
 
 RSpec.describe 'Mongo::Client instrumentation' do
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   let(:client) { Mongo::Client.new(*client_options) }
   let(:client_options) { [["#{host}:#{port}"], { database: database }] }

spec/ddtrace/contrib/mysql2/patcher_spec.rb

@@ -4,7 +4,7 @@
 require 'mysql2'
 
 RSpec.describe 'Mysql2::Client patcher' do
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   let(:client) do
     Mysql2::Client.new(

spec/ddtrace/contrib/racecar/patcher_spec.rb

@@ -5,7 +5,7 @@
 require 'active_support'
 require 'ddtrace'
 RSpec.describe 'Racecar patcher' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   def all_spans
     tracer.writer.spans(:keep)

spec/ddtrace/contrib/rack/distributed_spec.rb

@@ -8,7 +8,7 @@
 RSpec.describe 'Rack integration distributed tracing' do
   include Rack::Test::Methods
 
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:rack_options) { { tracer: tracer } }
 
   let(:spans) { tracer.writer.spans }

spec/ddtrace/contrib/rack/integration_spec.rb

@@ -9,7 +9,7 @@
 RSpec.describe 'Rack integration tests' do
   include Rack::Test::Methods
 
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:rack_options) { { tracer: tracer } }
 
   let(:spans) { tracer.writer.spans }

spec/ddtrace/contrib/rack/middleware_spec.rb

@@ -8,7 +8,7 @@
   subject(:middleware) { described_class.new(app) }
   let(:app) { instance_double(Rack::Builder) }
 
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:configuration_options) { { tracer: tracer } }
 
   before(:each) do

spec/ddtrace/contrib/rack/request_queuing_spec.rb

@@ -8,7 +8,7 @@
 RSpec.describe 'Rack integration request queuing' do
   include Rack::Test::Methods
 
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:rack_options) { { tracer: tracer } }
 
   let(:spans) { tracer.writer.spans }

spec/ddtrace/contrib/rack/resource_name_spec.rb

@@ -8,7 +8,7 @@
 RSpec.describe 'Rack integration with other middleware' do
   include Rack::Test::Methods
 
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:rack_options) do
     {
       application: app,

spec/ddtrace/contrib/rails/action_controller_spec.rb

@@ -1,7 +1,7 @@
 require 'ddtrace/contrib/rails/rails_helper'
 
 RSpec.describe 'ActionController tracing' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:rails_options) { { tracer: tracer } }
 
   before(:each) do

spec/ddtrace/contrib/rails/middleware_spec.rb

@@ -15,7 +15,7 @@ def index
     end)
   end
 
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   def all_spans
     tracer.writer.spans(:keep)

spec/ddtrace/contrib/rails/railtie_spec.rb

@@ -7,7 +7,7 @@
   before(:each) { skip 'Test not compatible with Rails < 4.0' if Rails.version < '4.0' }
   include_context 'Rails test application'
 
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   let(:routes) { { '/' => 'test#index' } }
   let(:controllers) { [controller] }

spec/ddtrace/contrib/rake/instrumentation_spec.rb

@@ -7,7 +7,7 @@
 require 'ddtrace/contrib/rake/patcher'
 
 RSpec.describe Datadog::Contrib::Rake::Instrumentation do
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:configuration_options) { { tracer: tracer, enabled: true } }
   let(:spans) { tracer.writer.spans }
   let(:span) { spans.first }

spec/ddtrace/contrib/redis/miniapp_spec.rb

@@ -6,7 +6,7 @@
 require 'ddtrace'
 
 RSpec.describe 'Redis mini app test' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   def all_spans
     tracer.writer.spans(:keep)

spec/ddtrace/contrib/redis/redis_spec.rb

@@ -6,7 +6,7 @@
 require 'ddtrace'
 
 RSpec.describe 'Redis test' do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
 
   def all_spans
     tracer.writer.spans(:keep)

spec/ddtrace/contrib/resque/instrumentation_spec.rb

@@ -6,7 +6,7 @@
 RSpec.describe 'Resque instrumentation' do
   include_context 'Resque job'
 
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:pin) { ::Resque.datadog_pin }
   let(:spans) { tracer.writer.spans }
   let(:span) { spans.first }

spec/ddtrace/contrib/rest_client/request_patch_spec.rb

@@ -5,7 +5,7 @@
 require 'restclient/request'
 
 RSpec.describe Datadog::Contrib::RestClient::RequestPatch do
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:rest_client_options) { {} }
 
   before do

spec/ddtrace/contrib/sequel/configuration_spec.rb

@@ -6,7 +6,7 @@
 require 'ddtrace/contrib/sequel/patcher'
 
 RSpec.describe 'Sequel configuration' do
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:spans) { tracer.writer.spans }
   let(:span) { spans.first }
 

spec/ddtrace/contrib/sequel/instrumentation_spec.rb

@@ -6,7 +6,7 @@
 require 'ddtrace/contrib/sequel/integration'
 
 RSpec.describe 'Sequel instrumentation' do
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:configuration_options) { { tracer: tracer } }
   let(:sequel) do
     Sequel.sqlite(':memory:').tap do |s|

spec/ddtrace/contrib/shoryuken/tracer_spec.rb

@@ -3,7 +3,7 @@
 require 'shoryuken'
 
 RSpec.describe Datadog::Contrib::Shoryuken::Tracer do
-  let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:options) { { tracer: tracer } }
   let(:spans) { tracer.writer.spans }
   let(:span) { spans.first }

spec/ddtrace/contrib/sinatra/activerecord_spec.rb

@@ -11,7 +11,7 @@
 RSpec.describe 'Sinatra instrumentation with ActiveRecord' do
   include Rack::Test::Methods
 
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:options) { { tracer: tracer } }
 
   let(:span) { spans.first }

spec/ddtrace/contrib/sinatra/multi_app_spec.rb

@@ -9,7 +9,7 @@
 RSpec.describe 'Sinatra instrumentation for multi-apps' do
   include Rack::Test::Methods
 
-  let(:tracer) { Datadog::Tracer.new(writer: FauxWriter.new) }
+  let(:tracer) { get_test_tracer }
   let(:options) { { tracer: tracer } }
 
   let(:span) { spans.first }