Added: Compatibility with Rails 5.2 built-in Redis store.

Appraisals

@@ -286,6 +286,12 @@ elsif Gem::Version.new('2.2.0') <= Gem::Version.new(RUBY_VERSION) \
     end
 
     appraise 'rails5-postgres-redis' do
+      gem 'rails', '~> 5.2.1'
+      gem 'pg', '< 1.0', platform: :ruby
+      gem 'redis'
+    end
+
+    appraise 'rails5-postgres-redis-activesupport' do
       gem 'rails', '~> 5.2.1'
       gem 'pg', '< 1.0', platform: :ruby
       gem 'redis-rails'
@@ -425,6 +431,12 @@ elsif Gem::Version.new('2.3.0') <= Gem::Version.new(RUBY_VERSION) \
     end
 
     appraise 'rails5-postgres-redis' do
+      gem 'rails', '~> 5.2.1'
+      gem 'pg', '< 1.0', platform: :ruby
+      gem 'redis'
+    end
+
+    appraise 'rails5-postgres-redis-activesupport' do
       gem 'rails', '~> 5.2.1'
       gem 'pg', '< 1.0', platform: :ruby
       gem 'redis-rails'

Rakefile

@@ -343,6 +343,7 @@ task :ci do
       sh 'bundle exec appraisal rails5-mysql2 rake test:rails'
       sh 'bundle exec appraisal rails5-postgres rake test:rails'
       sh 'bundle exec appraisal rails5-postgres-redis rake test:railsredis'
+      sh 'bundle exec appraisal rails5-postgres-redis-activesupport rake test:railsredis'
       sh 'bundle exec appraisal rails5-postgres-sidekiq rake test:railssidekiq'
       sh 'bundle exec appraisal rails5-postgres-sidekiq rake test:railsactivejob'
       sh 'bundle exec appraisal rails5-postgres rake test:railsdisableenv'
@@ -409,6 +410,7 @@ task :ci do
       sh 'bundle exec appraisal rails5-mysql2 rake test:rails'
       sh 'bundle exec appraisal rails5-postgres rake test:rails'
       sh 'bundle exec appraisal rails5-postgres-redis rake test:railsredis'
+      sh 'bundle exec appraisal rails5-postgres-redis-activesupport rake test:railsredis'
       sh 'bundle exec appraisal rails5-postgres-sidekiq rake test:railssidekiq'
       sh 'bundle exec appraisal rails5-postgres-sidekiq rake test:railsactivejob'
       sh 'bundle exec appraisal rails5-postgres rake test:railsdisableenv'

lib/ddtrace/contrib/active_support/cache/patcher.rb

@@ -1,6 +1,5 @@
 require 'ddtrace/contrib/patcher'
 require 'ddtrace/contrib/active_support/cache/instrumentation'
-# require 'ddtrace/contrib/active_support/cache/redis'
 
 module Datadog
   module Contrib

lib/ddtrace/contrib/active_support/cache/redis.rb

@@ -15,8 +15,13 @@ module Patcher
             # be redefined, and some of them not. The latest version of redis-activesupport
             # redefines write but leaves untouched read and delete:
             # https://github.com/redis-store/redis-activesupport/blob/master/lib/active_support/cache/redis_store.rb
+            #
+            # For Rails >= 5.2 w/o redis-activesupport...
+            # ActiveSupport includes a Redis cache store internally, and does not require these overrides.
+            # https://github.com/rails/rails/blob/master/activesupport/lib/active_support/cache/redis_cache_store.rb
             def patch_redis?(meth)
-              defined?(::ActiveSupport::Cache::RedisStore) \
+              !Gem.loaded_specs['redis-activesupport'].nil? \
+                && defined?(::ActiveSupport::Cache::RedisStore) \
                 && ::ActiveSupport::Cache::RedisStore.instance_methods(false).include?(meth)
             end
 

test/contrib/rails/apps/application.rb

@@ -11,7 +11,11 @@ class TestApplication < Rails::Application
     # common settings between all Rails versions
     def initialize(*args)
       super(*args)
-      redis_cache = [:redis_store, { url: ENV['REDIS_URL'] }]
+      redis_cache = if Gem.loaded_specs['redis-activesupport']
+                      [:redis_store, { url: ENV['REDIS_URL'] }]
+                    else
+                      [:redis_cache_store, { url: ENV['REDIS_URL'] }]
+                    end
       file_cache = [:file_store, '/tmp/ddtrace-rb/cache/']
 
       config.secret_key_base = 'f624861242e4ccf20eacb6bb48a886da'

test/contrib/rails/redis_cache_test.rb

@@ -18,16 +18,23 @@ class RedisCacheTracingTest < ActionController::TestCase
     @tracer = get_test_tracer
     Datadog.configuration[:rails][:tracer] = @tracer
     Datadog.configuration.use(:redis)
-
-    # get the Redis pin accessing private methods (only Rails 3.x)
-    driver = Rails.cache.instance_variable_get(:@data)
     Datadog.configure(client_from_driver(driver), tracer: @tracer)
   end
 
   teardown do
     Datadog.configuration[:rails][:tracer] = @original_tracer
   end
 
+  def driver
+    # For internal Redis store (Rails 5.2+), use the #redis method.
+    # For redis-activesupport, get the Redis pin accessing private methods (only Rails 3.x)
+    Rails.cache.respond_to?(:redis) ? Rails.cache.redis : Rails.cache.instance_variable_get(:@data)
+  end
+
+  def cache_store_name
+    Gem.loaded_specs['redis-activesupport'] ? 'redis_store' : 'redis_cache_store'
+  end
+
   test 'cache.read() and cache.fetch() are properly traced' do
     # read and fetch should behave exactly the same, and we shall
     # never see a read() having a fetch() as parent.
@@ -44,7 +51,7 @@ class RedisCacheTracingTest < ActionController::TestCase
       assert_equal(cache.span_type, 'cache')
       assert_equal(cache.resource, 'GET')
       assert_equal(cache.service, "#{app_name}-cache")
-      assert_equal(cache.get_tag('rails.cache.backend').to_s, 'redis_store')
+      assert_equal(cache.get_tag('rails.cache.backend').to_s, cache_store_name)
       assert_equal(cache.get_tag('rails.cache.key'), 'custom-key')
 
       assert_equal(redis.name, 'redis.command')
@@ -110,7 +117,7 @@ class RedisCacheTracingTest < ActionController::TestCase
     assert_equal(cache.span_type, 'cache')
     assert_equal(cache.resource, 'SET')
     assert_equal(cache.service, "#{app_name}-cache")
-    assert_equal(cache.get_tag('rails.cache.backend').to_s, 'redis_store')
+    assert_equal(cache.get_tag('rails.cache.backend').to_s, cache_store_name)
     assert_equal(cache.get_tag('rails.cache.key'), 'custom-key')
 
     assert_equal(redis.name, 'redis.command')
@@ -134,7 +141,7 @@ class RedisCacheTracingTest < ActionController::TestCase
     assert_equal(cache.span_type, 'cache')
     assert_equal(cache.resource, 'DELETE')
     assert_equal(cache.service, "#{app_name}-cache")
-    assert_equal(cache.get_tag('rails.cache.backend').to_s, 'redis_store')
+    assert_equal(cache.get_tag('rails.cache.backend').to_s, cache_store_name)
     assert_equal(cache.get_tag('rails.cache.key'), 'custom-key')
 
     assert_equal(del.name, 'redis.command')