Use database mutex locking

.travis.yml

@@ -10,10 +10,6 @@ before_script:
   - mysql -e 'create database acts_as_list;'
   - psql -c 'create database acts_as_list;' -U postgres
 rvm:
-  - 1.9.3
-  - 2.0.0
-  - 2.1.10
-  - 2.2.6
   - 2.3.6
   - 2.4.3
   - 2.5.0
@@ -22,37 +18,7 @@ env:
   - DB=mysql
   - DB=postgresql
 gemfile:
-  - gemfiles/rails_3_2.gemfile
-  - gemfiles/rails_4_1.gemfile
   - gemfiles/rails_4_2.gemfile
   - gemfiles/rails_5_0.gemfile
   - gemfiles/rails_5_1.gemfile
   - gemfiles/rails_5_2.gemfile
-matrix:
-  exclude:
-    - rvm: 1.9.3
-      gemfile: gemfiles/rails_5_0.gemfile
-    - rvm: 1.9.3
-      gemfile: gemfiles/rails_5_1.gemfile
-    - rvm: 1.9.3
-      gemfile: gemfiles/rails_5_2.gemfile
-    - rvm: 2.0.0
-      gemfile: gemfiles/rails_5_0.gemfile
-    - rvm: 2.0.0
-      gemfile: gemfiles/rails_5_1.gemfile
-    - rvm: 2.0.0
-      gemfile: gemfiles/rails_5_2.gemfile
-    - rvm: 2.1.10
-      gemfile: gemfiles/rails_5_0.gemfile
-    - rvm: 2.1.10
-      gemfile: gemfiles/rails_5_1.gemfile
-    - rvm: 2.1.10
-      gemfile: gemfiles/rails_5_2.gemfile
-    - rvm: 2.4.3
-      gemfile: gemfiles/rails_3_2.gemfile
-    - rvm: 2.4.3
-      gemfile: gemfiles/rails_4_1.gemfile
-    - rvm: 2.5.0
-      gemfile: gemfiles/rails_3_2.gemfile
-    - rvm: 2.5.0
-      gemfile: gemfiles/rails_4_1.gemfile

Appraisals

@@ -1,23 +1,3 @@
-appraise "rails-3-2" do
-  group :mysql do
-    gem "mysql2", "~> 0.3.21", platforms: [:ruby]
-  end
-  gem "activerecord", "~> 3.2.22.2"
-  group :test do
-    gem "after_commit_exception_notification"
-  end
-end
-
-appraise "rails-4-1" do
-  group :mysql do
-    gem "mysql2", "~> 0.3.21", platforms: [:ruby]
-  end
-  gem "activerecord", "~> 4.1.16"
-  group :test do
-    gem "after_commit_exception_notification"
-  end
-end
-
 appraise "rails-4-2" do
   group :mysql do
     gem "mysql2", "~> 0.4.10", platforms: [:ruby]

Gemfile

@@ -1,7 +1,5 @@
 source "http://rubygems.org"
 
-gem "rack", "~> 1", platforms: [:ruby_19, :ruby_20, :ruby_21]
-
 gemspec
 
 gem "rake"

acts_as_list.gemspec

@@ -14,7 +14,7 @@ Gem::Specification.new do |s|
   s.description           = 'This "acts_as" extension provides the capabilities for sorting and reordering a number of objects in a list. The class that has this specified needs to have a "position" column defined as an integer on the mapped database table.'
   s.license               = "MIT"
   s.rubyforge_project     = "acts_as_list"
-  s.required_ruby_version = ">= 1.9.2"
+  s.required_ruby_version = ">= 2.3.0"
 
   # Load Paths...
   s.files                 = `git ls-files`.split("\n")
@@ -24,6 +24,7 @@ Gem::Specification.new do |s|
 
 
   # Dependencies (installed via "bundle install")
-  s.add_dependency "activerecord", ">= 3.0"
+  s.add_dependency "activerecord", ">= 4.2"
+  s.add_dependency "with_advisory_lock", "~> 4.0"
   s.add_development_dependency "bundler", ">= 1.0.0"
 end

gemfiles/rails_4_2.gemfile

@@ -2,7 +2,6 @@
 
 source "http://rubygems.org"
 
-gem "rack", "~> 1", platforms: [:ruby_19, :ruby_20, :ruby_21]
 gem "rake"
 gem "appraisal"
 gem "activerecord", "~> 4.2.10"

gemfiles/rails_5_0.gemfile

@@ -2,7 +2,6 @@
 
 source "http://rubygems.org"
 
-gem "rack", "~> 1", platforms: [:ruby_19, :ruby_20, :ruby_21]
 gem "rake"
 gem "appraisal"
 gem "activerecord", "~> 5.0.6"

gemfiles/rails_5_1.gemfile

@@ -2,7 +2,6 @@
 
 source "http://rubygems.org"
 
-gem "rack", "~> 1", platforms: [:ruby_19, :ruby_20, :ruby_21]
 gem "rake"
 gem "appraisal"
 gem "activerecord", "~> 5.1.4"

gemfiles/rails_5_2.gemfile

@@ -2,10 +2,9 @@
 
 source "http://rubygems.org"
 
-gem "rack", "~> 1", platforms: [:ruby_19, :ruby_20, :ruby_21]
 gem "rake"
 gem "appraisal"
-gem "activerecord", "~> 5.2.0.rc1"
+gem "activerecord", "~> 5.2.1"
 
 group :development do
   gem "github_changelog_generator", "1.9.0"

lib/acts_as_list.rb

@@ -10,3 +10,4 @@
 require "acts_as_list/active_record/acts/no_update"
 require "acts_as_list/active_record/acts/sequential_updates_method_definer"
 require "acts_as_list/active_record/acts/active_record"
+require "acts_as_list/active_record/acts/advisory_lock"

lib/acts_as_list/active_record/acts/advisory_lock.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require 'with_advisory_lock'
+
+module ActiveRecord
+  module Acts #:nodoc:
+    module List #:nodoc:
+      module AdvisoryLock  #:nodoc:
+        def self.included(base)
+          base.prepend(InstanceMethods)
+        end
+
+        def self.acts_as_list_methods
+          ActiveRecord::Acts::List::InstanceMethods.public_instance_methods
+        end
+
+        def self.acts_as_list_lockable_methods
+          acts_as_list_methods.grep(/^(insert_|move_|remove_|set_|(dec|inc)rement_)/)
+        end
+
+        module InstanceMethods
+          AdvisoryLock.acts_as_list_lockable_methods.each do |m|
+            define_method(m) do |*args|
+              with_table_lock do
+                super(*args)
+              end
+            end
+          end
+
+          def advisory_lock_name
+            format('lock-%s', acts_as_list_class.to_s.downcase)
+          end
+
+          def with_table_lock
+            acts_as_list_class.with_advisory_lock(advisory_lock_name) do
+              yield
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/acts_as_list/active_record/acts/list.rb

@@ -37,6 +37,7 @@ def acts_as_list(options = {})
 
           include ActiveRecord::Acts::List::InstanceMethods
           include ActiveRecord::Acts::List::NoUpdate
+          include ActiveRecord::Acts::List::AdvisoryLock if configuration[:advisory_lock]
         end
 
         # This +acts_as+ extension provides the capabilities for sorting and reordering a number of objects in a list.

test/helper.rb

@@ -13,7 +13,7 @@
 end
 require "active_record"
 require "minitest/autorun"
-require "mocha/mini_test"
+require "mocha/minitest"
 require "#{File.dirname(__FILE__)}/../init"
 
 if defined?(ActiveRecord::VERSION) &&

test/test_list.rb

@@ -63,6 +63,26 @@ class ListMixin < Mixin
   acts_as_list column: "pos", scope: :parent
 end
 
+class SlowListMixin < Mixin
+  acts_as_list column: "pos", scope: :parent
+
+  before_create :slow_operation
+
+  def slow_operation
+    sleep 0.1
+  end
+end
+
+class SlowListMixinWithAdvisoryLock < Mixin
+  acts_as_list column: "pos", scope: :parent, advisory_lock: true
+
+  before_create :slow_operation
+
+  def slow_operation
+    sleep 0.1
+  end
+end
+
 class ListMixinSub1 < ListMixin
 end
 
@@ -256,6 +276,47 @@ def test_insert_race_condition
   end
 end
 
+class ListAdvisoryLockTest < ActsAsListTestCase
+  def setup
+    setup_db
+  end
+
+  def test_errors_without_lock
+    range = 1..10
+    threads = range.map do
+      Thread.new do
+        begin
+          SlowListMixin.create!(parent_id: 5)
+        rescue
+          # Retry ActiveRecord::ConnectionTimeoutError, etc
+          retry
+        end
+      end
+    end
+    threads.each(&:join)
+
+    assert(range.to_a != SlowListMixin.order(:pos).pluck(:pos))
+  end
+
+
+  def test_no_errors_with_lock
+    range = 1..10
+    threads = range.map do
+      Thread.new do
+        begin
+          SlowListMixinWithAdvisoryLock.create!(parent_id: 5)
+        rescue
+          # Retry ActiveRecord::ConnectionTimeoutError, etc
+          retry
+        end
+      end
+    end
+    threads.each(&:join)
+
+    assert_equal(range.to_a, SlowListMixinWithAdvisoryLock.order(:pos).pluck(:pos))
+  end
+end
+
 class ListWithCallbackTest < ActsAsListTestCase
 
   include Shared::List