[close rails#33907] Error when using "recyclable" cache keys with a store that does not support it

If you are using the "in cache versioning" also known as "recyclable cache keys" the cache store must be aware of this scheme, otherwise you will generate cache entries that never invalidate.

This PR adds a check to the initialization process to ensure that if recyclable cache keys are being used via 

```
config.active_record.cache_versioning = true
```

Then the cache store needs to show that it supports this versioning scheme. Cache stores can let Rails know that they support this scheme by adding a method `supports_in_cache_versioning?` and returning true.

Author: schneems

activerecord/lib/active_record/railtie.rb

@@ -88,6 +88,29 @@ class Railtie < Rails::Railtie # :nodoc:
       end
     end
 
+    initializer "Check for cache versioning support" do
+      config.after_initialize do |app|
+        ActiveSupport.on_load(:active_record) do
+          if app.config.active_record.cache_versioning && Rails.cache
+            unless Rails.cache.try(:supports_in_cache_versioning?)
+              raise <<-end_error
+
+You're using a cache store `#{Rails.cache.class}` that does not support
+"recyclable" cache keys, also known as "in cache versioning". To
+fix this issue either disable "recyclable" cache keys by setting:
+
+    config.active_record.cache_versioning = false
+
+Or switching to a cache store that supports this functionality:
+https://guides.rubyonrails.org/caching_with_rails.html#cache-stores
+
+end_error
+            end
+          end
+        end
+      end
+    end
+
     initializer "active_record.check_schema_cache_dump" do
       if config.active_record.delete(:use_schema_cache_dump)
         config.after_initialize do |app|

activesupport/lib/active_support/cache/file_store.rb

@@ -26,6 +26,13 @@ def initialize(cache_path, options = nil)
         @cache_path = cache_path.to_s
       end
 
+      # Advertise that this cache store can be used
+      # with "recyclable cache keys" otherwise known
+      # as cache versioning.
+      def supports_in_cache_versioning?
+        true
+      end
+
       # Deletes all items from the cache. In this case it deletes all the entries in the specified
       # file store directory except for .keep or .gitkeep. Be careful which directory is specified in your
       # config file when using +FileStore+ because everything in that directory will be deleted.

activesupport/lib/active_support/cache/mem_cache_store.rb

@@ -47,6 +47,13 @@ def write_entry(key, entry, options)
           end
       end
 
+      # Advertise that this cache store can be used
+      # with "recyclable cache keys" otherwise known
+      # as cache versioning.
+      def supports_in_cache_versioning?
+        true
+      end
+
       prepend Strategy::LocalCache
       prepend LocalCacheWithRaw
 

activesupport/lib/active_support/cache/memory_store.rb

@@ -30,6 +30,13 @@ def initialize(options = nil)
         @pruning = false
       end
 
+      # Advertise that this cache store can be used
+      # with "recyclable cache keys" otherwise known
+      # as cache versioning.
+      def supports_in_cache_versioning?
+        true
+      end
+
       # Delete all data stored in a given cache store.
       def clear(options = nil)
         synchronize do

activesupport/lib/active_support/cache/null_store.rb

@@ -12,6 +12,13 @@ module Cache
     class NullStore < Store
       prepend Strategy::LocalCache
 
+      # Advertise that this cache store can be used
+      # with "recyclable cache keys" otherwise known
+      # as cache versioning.
+      def supports_in_cache_versioning?
+        true
+      end
+
       def clear(options = nil)
       end
 

activesupport/lib/active_support/cache/redis_cache_store.rb

@@ -66,6 +66,13 @@ class RedisCacheStore < Store
       SCAN_BATCH_SIZE = 1000
       private_constant :SCAN_BATCH_SIZE
 
+      # Advertise that this cache store can be used
+      # with "recyclable cache keys" otherwise known
+      # as cache versioning.
+      def supports_in_cache_versioning?
+        true
+      end
+
       # Support raw values in the local cache strategy.
       module LocalCacheWithRaw # :nodoc:
         private

railties/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Raise an error when "recyclable cache keys" are being used by a cache store
+    that does not explicitly support it.
+
+    *Richard Schneeman*
+
 *   Support environment specific credentials file.
 
     For `production` environment look first for `config/credentials/production.yml.enc` file that can be decrypted by

railties/test/application/configuration_test.rb

@@ -124,6 +124,18 @@ class MyLogger < ::Logger
       assert_equal "MyLogger", Rails.application.config.logger.class.name
     end
 
+    test "raises an error if cache does not support recyclable cache keys" do
+      build_app(initializers: true)
+      add_to_env_config "production", "config.cache_store = Class.new {}.new"
+      add_to_env_config "production", "config.active_record.cache_versioning = true"
+
+      error = assert_raise(RuntimeError) do
+        app "production"
+      end
+
+      assert_match(/You're using a cache store/, error.message)
+    end
+
     test "a renders exception on pending migration" do
       add_to_config <<-RUBY
         config.active_record.migration_error    = :page_load