Make Solid Cache the default for new Rails apps

The defaults for the cache are pulled in from the [template](https://github.com/rails/solid_cache/blob/87fd0e9611237b5608b5e0f4197aec74fe333ca4/lib/generators/solid_cache/install/templates/config/solid_cache.yml.tt)
in Solid Cache. Currently 1 week max age and 256MB max size.

Right now this sets up Solid Cache to be used in development and
production - maybe we'd want to stick with a memory cache in development?

When using Sqlite, we'll use a separate database for the cache, with
the migrations for that db going into `db/cache/migrate`. We then need
to adjust the db change task to move the migrations if required.

For all databases we'll use a separate connection pool for the database
even if it points to the primary database. This stops cache queries
from being affected by primary database transactions.

As a result the `config/database.yml` templates have been converted to
the three-tier format. We could keep the two-tier format when not using
Solid Cache, but the templates would start to get messy.

Gemfile

@@ -40,6 +40,8 @@ gem "cgi", ">= 0.3.6", require: false
 
 gem "prism"
 
+gem "solid_cache", ">= 1.0.0"
+
 group :lint do
   gem "syntax_tree", "6.1.1", require: false
 end

Gemfile.lock

@@ -544,6 +544,10 @@ GEM
       rake
       serverengine (~> 2.0.5)
       thor
+    solid_cache (1.0.0)
+      activejob (>= 7.2)
+      activerecord (>= 7.2)
+      railties (>= 7.2)
     sorted_set (1.0.3)
       rbtree
       set (~> 1.0)
@@ -689,6 +693,7 @@ DEPENDENCIES
   selenium-webdriver (>= 4.20.0)
   sidekiq
   sneakers
+  solid_cache (>= 1.0.0)
   sprockets-rails (>= 2.0.0)
   sqlite3 (>= 2.0)
   stackprof

railties/lib/rails/generators/app_base.rb

@@ -114,6 +114,9 @@ def self.add_shared_options_for(name)
         class_option :skip_kamal,          type: :boolean, default: false,
                                            desc: "Skip Kamal setup"
 
+        class_option :skip_solid_cache,    type: :boolean, default: false,
+                                           desc: "Skip Solid Cache setup"
+
         class_option :dev,                 type: :boolean, default: nil,
                                            desc: "Set up the #{name} with Gemfile pointing to your Rails checkout"
 
@@ -158,6 +161,7 @@ def gemfile_entries # :doc:
           css_gemfile_entry,
           jbuilder_gemfile_entry,
           cable_gemfile_entry,
+          solid_cache_gemfile_entry,
         ].flatten.compact.select(&@gem_filter)
       end
 
@@ -392,6 +396,10 @@ def skip_asset_pipeline? # :doc:
         options[:skip_asset_pipeline]
       end
 
+      def skip_solid_cache?
+        options[:skip_solid_cache]
+      end
+
       def skip_sprockets?
         skip_asset_pipeline? || options[:asset_pipeline] != "sprockets"
       end
@@ -640,6 +648,13 @@ def cable_gemfile_entry
         GemfileEntry.new("redis", ">= 4.0.1", comment, {}, true)
       end
 
+      def solid_cache_gemfile_entry
+        return if options[:skip_solid_cache]
+
+        comment = "Use Solid Cache for caching (http://github.com/rails/solid_cache)"
+        GemfileEntry.new("solid_cache", ">= 1.0.0", comment, {}, false)
+      end
+
       def bundle_command(command, env = {})
         say_status :run, "bundle #{command}"
 

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -316,6 +316,7 @@ class AppGenerator < AppBase
             :skip_hotwire,
             :skip_javascript,
             :skip_jbuilder,
+            :skip_solid_cache,
             :skip_system_test,
           ],
           api: [
@@ -474,6 +475,16 @@ def create_devcontainer_files
         build(:devcontainer)
       end
 
+      def install_solid_cache
+        unless skip_solid_cache?
+          if options[:database] == "sqlite3"
+            rails_command "DATABASE=cache solid_cache:install", inline: false, capture: options[:quiet]
+          else
+            rails_command "solid_cache:install", inline: false, capture: options[:quiet]
+          end
+        end
+      end
+
       def delete_app_assets_if_api_option
         if options[:api]
           remove_dir "app/assets"

railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml.tt

@@ -22,15 +22,25 @@ default: &default
 <% end -%>
 
 development:
-  <<: *default
-  database: <%= app_name %>_development
+  primary:<% unless options[:skip_solid_cache] %> &development_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_development
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *development_primary
+<% end -%>
 
 # Warning: The database defined as "test" will be erased and
 # re-generated from your development database when you run "rake".
 # Do not set this db to the same as development or production.
 test:
-  <<: *default
-  database: <%= app_name %>_test
+  primary:<% unless options[:skip_solid_cache] %> &test_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_test
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *test_primary
+<% end -%>
 
 # As with config/credentials.yml, you never want to store sensitive information,
 # like your database password, in your source code. If your source code is
@@ -53,7 +63,12 @@ test:
 # for a full overview on how database connection configuration can be specified.
 #
 production:
-  <<: *default
-  database: <%= app_name %>_production
-  username: <%= app_name %>
-  password: <%%= ENV["<%= app_name.upcase %>_DATABASE_PASSWORD"] %>
+  primary:<% unless options[:skip_solid_cache] %> &production_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_production
+    username: <%= app_name %>
+    password: <%%= ENV["<%= app_name.upcase %>_DATABASE_PASSWORD"] %>
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *production_primary
+<% end -%>

railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml.tt

@@ -27,42 +27,52 @@ default: &default
 <% end %>
 
 development:
-  <<: *default
-  database: <%= app_name %>_development
+  primary:<% unless options[:skip_solid_cache] %> &development_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_development
 
-  # The specified database role being used to connect to PostgreSQL.
-  # To create additional roles in PostgreSQL see `$ createuser --help`.
-  # When left blank, PostgreSQL will use the default role. This is
-  # the same name as the operating system user running Rails.
-  #username: <%= app_name %>
+    # The specified database role being used to connect to PostgreSQL.
+    # To create additional roles in PostgreSQL see `$ createuser --help`.
+    # When left blank, PostgreSQL will use the default role. This is
+    # the same name as the operating system user running Rails.
+    #username: <%= app_name %>
 
-  # The password associated with the PostgreSQL role (username).
-  #password:
+    # The password associated with the PostgreSQL role (username).
+    #password:
 
-  # Connect on a TCP socket. Omitted by default since the client uses a
-  # domain socket that doesn't need configuration. Windows does not have
-  # domain sockets, so uncomment these lines.
-  #host: localhost
+    # Connect on a TCP socket. Omitted by default since the client uses a
+    # domain socket that doesn't need configuration. Windows does not have
+    # domain sockets, so uncomment these lines.
+    #host: localhost
 
-  # The TCP port the server listens on. Defaults to 5432.
-  # If your server runs on a different port number, change accordingly.
-  #port: 5432
+    # The TCP port the server listens on. Defaults to 5432.
+    # If your server runs on a different port number, change accordingly.
+    #port: 5432
 
-  # Schema search path. The server defaults to $user,public
-  #schema_search_path: myapp,sharedapp,public
+    # Schema search path. The server defaults to $user,public
+    #schema_search_path: myapp,sharedapp,public
 
-  # Minimum log levels, in increasing order:
-  #   debug5, debug4, debug3, debug2, debug1,
-  #   log, notice, warning, error, fatal, and panic
-  # Defaults to warning.
-  #min_messages: notice
+    # Minimum log levels, in increasing order:
+    #   debug5, debug4, debug3, debug2, debug1,
+    #   log, notice, warning, error, fatal, and panic
+    # Defaults to warning.
+    #min_messages: notice
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *development_primary
+<% end -%>
 
 # Warning: The database defined as "test" will be erased and
 # re-generated from your development database when you run "rake".
 # Do not set this db to the same as development or production.
 test:
-  <<: *default
-  database: <%= app_name %>_test
+  primary: <% unless options[:skip_solid_cache] %> &test_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_test
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *test_primary
+<% end -%>
 
 # As with config/credentials.yml, you never want to store sensitive information,
 # like your database password, in your source code. If your source code is
@@ -85,7 +95,12 @@ test:
 # for a full overview on how database connection configuration can be specified.
 #
 production:
-  <<: *default
-  database: <%= app_name %>_production
-  username: <%= app_name %>
-  password: <%%= ENV["<%= app_name.upcase %>_DATABASE_PASSWORD"] %>
+  primary:<% unless options[:skip_solid_cache] %> &production_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_production
+    username: <%= app_name %>
+    password: <%%= ENV["<%= app_name.upcase %>_DATABASE_PASSWORD"] %>
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *production_primary
+<% end -%>

railties/lib/rails/generators/rails/app/templates/config/databases/sqlite3.yml.tt

@@ -10,16 +10,29 @@ default: &default
   timeout: 5000
 
 development:
-  <<: *default
-  database: storage/development.sqlite3
+  primary:
+    <<: *default
+    database: storage/development.sqlite3
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *default
+    database: storage/development_cache.sqlite3
+    migrations_paths: "db/cache/migrate"
+<%- end -%>
 
 # Warning: The database defined as "test" will be erased and
 # re-generated from your development database when you run "rake".
 # Do not set this db to the same as development or production.
 test:
-  <<: *default
-  database: storage/test.sqlite3
-
+  primary:
+    <<: *default
+    database: storage/test.sqlite3
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *default
+    database: storage/test_cache.sqlite3
+    migrations_paths: "db/cache/migrate"
+<%- end -%>
 
 <%- if options.skip_kamal? -%>
 # SQLite3 write its data on the local filesystem, as such it requires
@@ -29,12 +42,26 @@ test:
 # Similarly, if you deploy your application as a Docker container, you must
 # ensure the database is located in a persisted volume.
 production:
-  <<: *default
-  # database: path/to/persistent/storage/production.sqlite3
+  primary:
+    <<: *default
+    # database: path/to/persistent/storage/production.sqlite3
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *default
+    # database: path/to/persistent/storage/production_cache.sqlite3
+    # migrations_paths: "db/cache/migrate"
+<%- end -%>
 <%- else -%>
 # Store production database in the storage/ directory, which by default
 # is mounted as a persistent Docker volume in config/deploy.yml.
 production:
-  <<: *default
-  database: storage/production.sqlite3
-<%- end -%>
+  primary:
+    <<: *default
+    database: storage/production.sqlite3
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *default
+    database: storage/production_cache.sqlite3
+    migrations_paths: "db/cache/migrate"
+<%- end -%>
+<%- end -%>

railties/lib/rails/generators/rails/app/templates/config/databases/trilogy.yml.tt

@@ -22,15 +22,25 @@ default: &default
 <% end -%>
 
 development:
-  <<: *default
-  database: <%= app_name %>_development
+  primary:<% unless options[:skip_solid_cache] %> &development_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_development
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *development_primary
+<% end -%>
 
 # Warning: The database defined as "test" will be erased and
 # re-generated from your development database when you run "rake".
 # Do not set this db to the same as development or production.
 test:
-  <<: *default
-  database: <%= app_name %>_test
+  primary:<% unless options[:skip_solid_cache] %> &test_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_test
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *test_primary
+<% end -%>
 
 # As with config/credentials.yml, you never want to store sensitive information,
 # like your database password, in your source code. If your source code is
@@ -53,7 +63,12 @@ test:
 # for a full overview on how database connection configuration can be specified.
 #
 production:
-  <<: *default
-  database: <%= app_name %>_production
-  username: <%= app_name %>
-  password: <%%= ENV["<%= app_name.upcase %>_DATABASE_PASSWORD"] %>
+  primary:<% unless options[:skip_solid_cache] %> &production_primary<% end %>
+    <<: *default
+    database: <%= app_name %>_production
+    username: <%= app_name %>
+    password: <%%= ENV["<%= app_name.upcase %>_DATABASE_PASSWORD"] %>
+<% unless options[:skip_solid_cache] -%>
+  cache:
+    <<: *production_primary
+<% end -%>

railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt

@@ -30,7 +30,11 @@ Rails.application.configure do
   end
 
   # Change this to :null_store to avoid any caching
+  <%- if options[:skip_solid_cache] -%>
   config.cache_store = :memory_store
+  <%- else -%>
+  config.cache_store = :solid_cache_store
+  <% end %>
   <%- unless skip_active_storage? -%>
 
   # Store uploaded files on the local file system (see config/storage.yml for options).

railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt

@@ -73,8 +73,13 @@ Rails.application.configure do
   # want to log everything, set the level to "debug".
   config.log_level = ENV.fetch("RAILS_LOG_LEVEL", "info")
 
+  <%- if options[:skip_solid_cache] -%>
   # Use a different cache store in production.
   # config.cache_store = :mem_cache_store
+  <%- else -%>
+  # Cache with Solid Cache
+  config.cache_store = :solid_cache_store
+  <% end %>
 
   <%- unless options[:skip_active_job] -%>
   # Use a real queuing backend for Active Job (and separate queues per environment).