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-rw-r--r--railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt20
1 files changed, 20 insertions, 0 deletions
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
index 08befd9196..94f7dd0c79 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
@@ -98,4 +98,24 @@ Rails.application.configure do
# Do not dump schema after migrations.
config.active_record.dump_schema_after_migration = false
<%- end -%>
+
+ # Inserts middleware to perform automatic connection switching.
+ # The `database_selector` hash is used to pass options to the DatabaseSelector
+ # middleware. The `delay` is used to determine how long to wait after a write
+ # to send a subsequent read to the primary.
+ #
+ # The `database_resolver` class is used by the middleware to determine which
+ # database is appropriate to use based on the time delay.
+ #
+ # The `database_operations` class is used by the middleware to set timestamps
+ # for the last write to the primary. The resolver uses the operations class
+ # timestamps to determine how long to wait before reading from the replica.
+ #
+ # By default Rails will store a last write timestamp in the session. The
+ # DatabaseSelector middleware is designed as such you can define your own
+ # strategy for connection switching and pass that into the middleware through
+ # these configuration options.
+ # config.active_record.database_selector = { delay: 2.seconds }
+ # config.active_record.database_resolver = ActiveRecord::Middleware::DatabaseSelector::Resolver
+ # config.active_record.database_operations = ActiveRecord::Middleware::DatabaseSelector::Resolver::Session
end