From a8860c5644ca7a3fe24396990b98eb0e312e39ea Mon Sep 17 00:00:00 2001
From: David Elner <david@davidelner.com>
Date: Mon, 6 May 2019 11:28:43 -0400
Subject: [PATCH] Changed: reload_cache_store in Rails instead of
 ActiveSupport.

---
 lib/ddtrace/contrib/active_support/patcher.rb | 22 -------------------
 lib/ddtrace/contrib/rails/framework.rb        | 22 +++++++++++++++++++
 lib/ddtrace/contrib/redis/patcher.rb          |  6 ++++-
 3 files changed, 27 insertions(+), 23 deletions(-)

diff --git a/lib/ddtrace/contrib/active_support/patcher.rb b/lib/ddtrace/contrib/active_support/patcher.rb
index 27864b99bdf..10ba6d34fcb 100644
--- a/lib/ddtrace/contrib/active_support/patcher.rb
+++ b/lib/ddtrace/contrib/active_support/patcher.rb
@@ -33,7 +33,6 @@ def patch_cache_store
             patch_cache_store_fetch
             patch_cache_store_write
             patch_cache_store_delete
-            reload_cache_store
           end
         end
 
@@ -163,27 +162,6 @@ def delete(*args, &block)
             end
           end
         end
-
-        def self.reload_cache_store
-          redis = Datadog.registry[:redis]
-          return unless redis && redis.patcher.patched?
-
-          return unless defined?(::ActiveSupport::Cache::RedisStore) &&
-                        defined?(::Rails) &&
-                        ::Rails.respond_to?(:cache) &&
-                        ::Rails.cache.is_a?(::ActiveSupport::Cache::RedisStore)
-
-          Tracer.log.debug('Reloading redis cache store')
-
-          # backward compatibility: Rails 3.x doesn't have `cache=` method
-          cache_store = ::Rails.configuration.cache_store
-          cache_instance = ::ActiveSupport::Cache.lookup_store(cache_store)
-          if ::Rails::VERSION::MAJOR.to_i == 3
-            silence_warnings { Object.const_set 'RAILS_CACHE', cache_instance }
-          elsif ::Rails::VERSION::MAJOR.to_i > 3
-            ::Rails.cache = cache_instance
-          end
-        end
       end
     end
   end
diff --git a/lib/ddtrace/contrib/rails/framework.rb b/lib/ddtrace/contrib/rails/framework.rb
index 586ee14d0fa..8eebb241eb6 100644
--- a/lib/ddtrace/contrib/rails/framework.rb
+++ b/lib/ddtrace/contrib/rails/framework.rb
@@ -63,6 +63,28 @@ def self.activate_active_support!(config)
             service_name: config[:cache_service],
             tracer: config[:tracer]
           )
+
+          reload_cache_store
+        end
+
+        def self.reload_cache_store
+          return unless Datadog.registry[:redis] &&
+                        Datadog.registry[:redis].patcher.patched?
+
+          return unless defined?(::ActiveSupport::Cache::RedisStore) &&
+                        ::Rails.respond_to?(:cache) &&
+                        ::Rails.cache.is_a?(::ActiveSupport::Cache::RedisStore)
+
+          Tracer.log.debug('Reloading redis cache store')
+
+          # backward compatibility: Rails 3.x doesn't have `cache=` method
+          cache_store = ::Rails.configuration.cache_store
+          cache_instance = ::ActiveSupport::Cache.lookup_store(cache_store)
+          if ::Rails::VERSION::MAJOR.to_i == 3
+            silence_warnings { Object.const_set 'RAILS_CACHE', cache_instance }
+          elsif ::Rails::VERSION::MAJOR.to_i > 3
+            ::Rails.cache = cache_instance
+          end
         end
 
         def self.activate_active_record!(config)
diff --git a/lib/ddtrace/contrib/redis/patcher.rb b/lib/ddtrace/contrib/redis/patcher.rb
index 78248567222..d4035ea2fde 100644
--- a/lib/ddtrace/contrib/redis/patcher.rb
+++ b/lib/ddtrace/contrib/redis/patcher.rb
@@ -25,7 +25,11 @@ def patch
               require 'ddtrace/contrib/redis/quantize'
 
               patch_redis_client
-              RailsCachePatcher.reload_cache_store if Datadog.registry[:rails].patcher.patched?
+
+              # Reload the Rails cache, if defined, so instrumentation is available.
+              if Datadog.registry[:rails] && Datadog.registry[:rails].patcher.patched?
+                Contrib::Rails::Framework.reload_cache_store
+              end
             rescue StandardError => e
               Datadog::Tracer.log.error("Unable to apply Redis integration: #{e}")
             end