1 files changed, 46 insertions, 0 deletions
diff --git a/activestorage/lib/active_storage/service/mirror_service.rb b/activestorage/lib/active_storage/service/mirror_service.rb
new file mode 100644
index 0000000000..7c407f2730
--- /dev/null
+++ b/activestorage/lib/active_storage/service/mirror_service.rb
@@ -0,0 +1,46 @@
+require "active_support/core_ext/module/delegation"
+
+# Wraps a set of mirror services and provides a single `ActiveStorage::Service` object that will all
+# have the files uploaded to them. A `primary` service is designated to answer calls to `download`, `exists?`,
+# and `url`.
+class ActiveStorage::Service::MirrorService < ActiveStorage::Service
+  attr_reader :primary, :mirrors
+
+  delegate :download, :exist?, :url, to: :primary
+
+  # Stitch together from named services.
+  def self.build(primary:, mirrors:, configurator:, **options) #:nodoc:
+    new \
+      primary: configurator.build(primary),
+      mirrors: mirrors.collect { |name| configurator.build name }
+  end
+
+  def initialize(primary:, mirrors:)
+    @primary, @mirrors = primary, mirrors
+  end
+
+  # Upload the `io` to the `key` specified to all services. If a `checksum` is provided, all services will
+  # ensure a match when the upload has completed or raise an `ActiveStorage::IntegrityError`.
+  def upload(key, io, checksum: nil)
+    each_service.collect do |service|
+      service.upload key, io.tap(&:rewind), checksum: checksum
+    end
+  end
+
+  # Delete the file at the `key` on all services.
+  def delete(key)
+    perform_across_services :delete, key
+  end
+
+  private
+    def each_service(&block)
+      [ primary, *mirrors ].each(&block)
+    end
+
+    def perform_across_services(method, *args)
+      # FIXME: Convert to be threaded
+      each_service.collect do |service|
+        service.public_send method, *args
+      end
+    end
+end