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rails--rails/activerecord/lib/active_record.rb
eileencodes 1ee4a8812f
Move advisory lock to it's own connection
This PR moves advisory lock to it's own connection instead of
`ActiveRecord::Base` to fix #37748. As a note the issue is present on
both mysql and postgres. We don't see it on sqlite3 because sqlite3
doesn't support advisory locks.

The underlying problem only appears if:

1) the app is using multiple databases, and therefore establishing a new
connetion in the abstract models
2) the app has a migration that loads a model (ex `Post.update_all`)
which causes that new connection to get established.

This is because when Rails runs migrations the default connections are
established, the lock is taken out on the `ActiveRecord::Base`
connection. When the migration that calls a model is loaded, a new
connection will be established and the lock will automatically be
released.

When Rails goes to release the lock in the ensure block it will find
that the connection has been closed. Even if the connection wasn't
closed the lock would no longer exist on that connection.

We originally considered checking if the connection was active, but
ultimately that would hide that the advisory locks weren't working
correctly because there'd be no lock to release.

We also considered making the lock more granular - that it only blocked
on each migration individually instead of all the migrations for that
connection. This might be the right move going forward, but right now
multi-db migrations that load models are very broken in Rails 6.0 and
master.

John and I don't love this fix, it requires a bit too much knowledge of
internals and how Rails picks up connections. However, it does fix the
issue, makes the lock more global, and makes the lock more resilient to
changing connections.

Co-authored-by: John Crepezzi <john.crepezzi@gmail.com>
2020-01-23 14:36:32 -05:00

187 lines
5.1 KiB
Ruby

# frozen_string_literal: true
#--
# Copyright (c) 2004-2020 David Heinemeier Hansson
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#++
require "active_support"
require "active_support/rails"
require "active_model"
require "arel"
require "yaml"
require "active_record/version"
require "active_model/attribute_set"
require "active_record/errors"
module ActiveRecord
extend ActiveSupport::Autoload
autoload :AdvisoryLockBase
autoload :Base
autoload :Callbacks
autoload :Core
autoload :ConnectionHandling
autoload :CounterCache
autoload :DynamicMatchers
autoload :Enum
autoload :InternalMetadata
autoload :Explain
autoload :Inheritance
autoload :Integration
autoload :Migration
autoload :Migrator, "active_record/migration"
autoload :ModelSchema
autoload :NestedAttributes
autoload :NoTouching
autoload :TouchLater
autoload :Persistence
autoload :QueryCache
autoload :Querying
autoload :ReadonlyAttributes
autoload :RecordInvalid, "active_record/validations"
autoload :Reflection
autoload :RuntimeRegistry
autoload :Sanitization
autoload :Schema
autoload :SchemaDumper
autoload :SchemaMigration
autoload :Scoping
autoload :Serialization
autoload :StatementCache
autoload :Store
autoload :Suppressor
autoload :Timestamp
autoload :Transactions
autoload :Translation
autoload :Validations
autoload :SecureToken
autoload :DatabaseSelector, "active_record/middleware/database_selector"
eager_autoload do
autoload :ConnectionAdapters
autoload :Aggregations
autoload :Associations
autoload :AttributeAssignment
autoload :AttributeMethods
autoload :AutosaveAssociation
autoload :LegacyYamlAdapter
autoload :Relation
autoload :AssociationRelation
autoload :NullRelation
autoload_under "relation" do
autoload :QueryMethods
autoload :FinderMethods
autoload :Calculations
autoload :PredicateBuilder
autoload :SpawnMethods
autoload :Batches
autoload :Delegation
end
autoload :Result
autoload :TableMetadata
autoload :Type
end
module Coders
autoload :YAMLColumn, "active_record/coders/yaml_column"
autoload :JSON, "active_record/coders/json"
end
module AttributeMethods
extend ActiveSupport::Autoload
eager_autoload do
autoload :BeforeTypeCast
autoload :Dirty
autoload :PrimaryKey
autoload :Query
autoload :Read
autoload :TimeZoneConversion
autoload :Write
autoload :Serialization
end
end
module Locking
extend ActiveSupport::Autoload
eager_autoload do
autoload :Optimistic
autoload :Pessimistic
end
end
module Scoping
extend ActiveSupport::Autoload
eager_autoload do
autoload :Named
autoload :Default
end
end
module Middleware
extend ActiveSupport::Autoload
autoload :DatabaseSelector, "active_record/middleware/database_selector"
end
module Tasks
extend ActiveSupport::Autoload
autoload :DatabaseTasks
autoload :SQLiteDatabaseTasks, "active_record/tasks/sqlite_database_tasks"
autoload :MySQLDatabaseTasks, "active_record/tasks/mysql_database_tasks"
autoload :PostgreSQLDatabaseTasks,
"active_record/tasks/postgresql_database_tasks"
end
autoload :TestDatabases, "active_record/test_databases"
autoload :TestFixtures, "active_record/fixtures"
def self.eager_load!
super
ActiveRecord::Locking.eager_load!
ActiveRecord::Scoping.eager_load!
ActiveRecord::Associations.eager_load!
ActiveRecord::AttributeMethods.eager_load!
ActiveRecord::ConnectionAdapters.eager_load!
end
end
ActiveSupport.on_load(:active_record) do
Arel::Table.engine = self
end
ActiveSupport.on_load(:i18n) do
I18n.load_path << File.expand_path("active_record/locale/en.yml", __dir__)
end
YAML.load_tags["!ruby/object:ActiveRecord::AttributeSet"] = "ActiveModel::AttributeSet"
YAML.load_tags["!ruby/object:ActiveRecord::Attribute::FromDatabase"] = "ActiveModel::Attribute::FromDatabase"
YAML.load_tags["!ruby/object:ActiveRecord::LazyAttributeHash"] = "ActiveModel::LazyAttributeHash"