[feature] purge unattached active storage blob

Addresses: #1083

DEMO:


https://user-images.githubusercontent.com/50227291/219999900-c683255b-018c-4208-8b33-70b541494815.mov

Co-authored-by: Pralish Kayastha <50227291+Pralish@users.noreply.github.com>

config/schedule.rb

@@ -41,4 +41,5 @@
 
 every 1.day do
   rake "maintenance:clear_discarded_api_actions"
+  rake "active_storage:purge_unattached"
 end

lib/tasks/active_storage.rake

@@ -0,0 +1,13 @@
+# https://github.com/rails/rails/blob/main/guides/source/active_storage_overview.md#purging-unattached-uploads
+namespace :active_storage do
+  desc "Purges unattached Active Storage blobs."
+
+  task purge_unattached: :environment do
+    Subdomain.all_with_public_schema.each do |subdomain|
+      Apartment::Tenant.switch subdomain.name do
+        p "** Purging unattached Active Storage blobs for #{subdomain.name}** @ #{Time.now}"
+        ActiveStorage::Blob.unattached.where('active_storage_blobs.created_at <= ?', 1.day.ago).find_each(&:purge_later)
+      end
+    end
+  end
+end

test/tasks/purge_unattached_task_test.rb

@@ -0,0 +1,48 @@
+require 'test_helper'
+require 'rake'
+
+class PurgeUnattachedTaskTest < ActiveSupport::TestCase
+  include Rake::DSL
+
+  def setup
+    Rake.application.rake_require('tasks/active_storage')
+    Rake::Task.define_task(:environment)
+    Sidekiq::Testing.fake!
+  end
+
+  test "purges only unattached Active Storage blobs that are older than 1 day" do
+    attached_blob = create_attached_blob
+    unattached_blob = create_unattached_blob
+
+    # Wait for the unattached blob to be older than 1 day
+    travel 2.days
+
+    another_unattached_blob = create_unattached_blob
+
+    perform_enqueued_jobs do
+      Rake::Task['active_storage:purge_unattached'].invoke
+      Sidekiq::Worker.drain_all
+    end
+
+    # purges unattached blob older than 1 day
+    assert_not ActiveStorage::Blob.exists?(unattached_blob.id)
+
+    # does not purge attached blob
+    assert ActiveStorage::Blob.exists?(attached_blob.id)
+
+    # does not purge unattached blob newer than 1 day
+    assert ActiveStorage::Blob.exists?(another_unattached_blob.id)
+  end
+
+  private
+
+  def create_attached_blob
+    user = users(:public)
+    user.avatar.attach(io: File.open(Rails.root.join('test', 'fixtures', 'files', 'fixture_image.png')), filename: 'fixture_image.png', content_type: 'image/png')
+    user.avatar.blob
+  end
+
+  def create_unattached_blob
+    ActiveStorage::Blob.create_after_upload!(io: StringIO.new('unattached blob data'), filename: 'unattached.txt', content_type: 'text/plain')
+  end
+end