From e4c197c7698e204d0c74a2ece20adf831c2f9a8d Mon Sep 17 00:00:00 2001
From: Matthew Draper <matthew@trebex.net>
Date: Tue, 11 Apr 2017 08:10:24 +0930
Subject: Add comprehensive locking around DB transactions
Transactional-fixture using tests with racing threads and inter-thread
synchronisation inside transaction blocks will now deadlock... but
without this, they would just crash.
In 5.0, the threads didn't share a connection at all, so it would've
worked... but with the main thread inside the fixture transaction, they
wouldn't've been able to see each other.
So: as far as I can tell, the set of operations this "breaks" never had
a compelling use case. Meanwhile, it provides an increased level of
coherency to the operational feel of transactional fixtures.
If this does cause anyone problems, they're probably best off disabling
transactional fixtures on the affected tests, and managing transactions
themselves.
---
.../connection_adapters/abstract/transaction.rb | 88 ++++++++++++----------
.../connection_adapters/abstract_adapter.rb | 2 +-
.../connection_adapters/postgresql_adapter.rb | 32 +++++---
3 files changed, 70 insertions(+), 52 deletions(-)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
index 6bb072dd73..19b7821494 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
@@ -149,57 +149,67 @@ module ActiveRecord
end
def begin_transaction(options = {})
- run_commit_callbacks = !current_transaction.joinable?
- transaction =
- if @stack.empty?
- RealTransaction.new(@connection, options, run_commit_callbacks: run_commit_callbacks)
- else
- SavepointTransaction.new(@connection, "active_record_#{@stack.size}", options,
- run_commit_callbacks: run_commit_callbacks)
- end
+ @connection.lock.synchronize do
+ run_commit_callbacks = !current_transaction.joinable?
+ transaction =
+ if @stack.empty?
+ RealTransaction.new(@connection, options, run_commit_callbacks: run_commit_callbacks)
+ else
+ SavepointTransaction.new(@connection, "active_record_#{@stack.size}", options,
+ run_commit_callbacks: run_commit_callbacks)
+ end
- @stack.push(transaction)
- transaction
+ @stack.push(transaction)
+ transaction
+ end
end
def commit_transaction
- transaction = @stack.last
+ @connection.lock.synchronize do
+ transaction = @stack.last
- begin
- transaction.before_commit_records
- ensure
- @stack.pop
- end
+ begin
+ transaction.before_commit_records
+ ensure
+ @stack.pop
+ end
- transaction.commit
- transaction.commit_records
+ transaction.commit
+ transaction.commit_records
+ end
end
def rollback_transaction(transaction = nil)
- transaction ||= @stack.pop
- transaction.rollback
- transaction.rollback_records
+ @connection.lock.synchronize do
+ transaction ||= @stack.pop
+ transaction.rollback
+ transaction.rollback_records
+ end
end
def within_new_transaction(options = {})
- transaction = begin_transaction options
- yield
- rescue Exception => error
- if transaction
- rollback_transaction
- after_failure_actions(transaction, error)
- end
- raise
- ensure
- unless error
- if Thread.current.status == "aborting"
- rollback_transaction if transaction
- else
- begin
- commit_transaction
- rescue Exception
- rollback_transaction(transaction) unless transaction.state.completed?
- raise
+ @connection.lock.synchronize do
+ begin
+ transaction = begin_transaction options
+ yield
+ rescue Exception => error
+ if transaction
+ rollback_transaction
+ after_failure_actions(transaction, error)
+ end
+ raise
+ ensure
+ unless error
+ if Thread.current.status == "aborting"
+ rollback_transaction if transaction
+ else
+ begin
+ commit_transaction
+ rescue Exception
+ rollback_transaction(transaction) unless transaction.state.completed?
+ raise
+ end
+ end
end
end
end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 96083e6519..85d6fbe8b3 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -74,7 +74,7 @@ module ActiveRecord
SIMPLE_INT = /\A\d+\z/
attr_accessor :visitor, :pool
- attr_reader :schema_cache, :owner, :logger, :prepared_statements
+ attr_reader :schema_cache, :owner, :logger, :prepared_statements, :lock
alias :in_use? :owner
def self.type_cast_config_to_integer(config)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 0ad114165e..7ae9bd9a5f 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -239,7 +239,9 @@ module ActiveRecord
# Is this connection alive and ready for queries?
def active?
- @connection.query "SELECT 1"
+ @lock.synchronize do
+ @connection.query "SELECT 1"
+ end
true
rescue PG::Error
false
@@ -247,26 +249,32 @@ module ActiveRecord
# Close then reopen the connection.
def reconnect!
- super
- @connection.reset
- configure_connection
+ @lock.synchronize do
+ super
+ @connection.reset
+ configure_connection
+ end
end
def reset!
- clear_cache!
- reset_transaction
- unless @connection.transaction_status == ::PG::PQTRANS_IDLE
- @connection.query "ROLLBACK"
+ @lock.synchronize do
+ clear_cache!
+ reset_transaction
+ unless @connection.transaction_status == ::PG::PQTRANS_IDLE
+ @connection.query "ROLLBACK"
+ end
+ @connection.query "DISCARD ALL"
+ configure_connection
end
- @connection.query "DISCARD ALL"
- configure_connection
end
# Disconnects from the database if already connected. Otherwise, this
# method does nothing.
def disconnect!
- super
- @connection.close rescue nil
+ @lock.synchronize do
+ super
+ @connection.close rescue nil
+ end
end
def native_database_types #:nodoc:
--
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