使用 RSpec 测试并行事务 [英] Testing parallel transactions using RSpec

问题描述

有没有办法使用 RSpec 测试并行事务?说我有一个银行账户余额需要在减少或增加之前锁定在交易中.但是，目前，虽然我关闭了 RSpec transactional_fixtures 选项，但我无法在两个单独的线程中启动 2 个并行事务.出于某种原因，两者都挂了.给定帐户是一个模型然后这个规范将挂起:

Is there any way to test parallel transaction using RSpec? Saying I have a bank account balance that need to be locked inside a transaction before it is decreased or increased. However, currently, although I have turned off RSpec transactional_fixtures option, I cannot launch 2 parallel transaction in two separated threads. For some reason, both are hung. Given Account is a model Then this spec will hang:

it "should ensure operations are performed correctly" do
  @account = Account.create(:balance => 0)
  threads = []
  (0..1).each do |index|
    threads << Thread.new do
      Account.transaction do
        account = Account.find(@account.id, :lock => true)
        account.balance += 100
        sleep 0.5
        account.save!
      end
    end
  end
  threads.each{|t|t.join}
  @account.reload.balance.should == 200
end

有什么办法可以不挂掉，同时还能展示交易能力?

Is there any way to make it not hang while still be able to demonstrate the ability of transaction?

推荐答案

您需要在线程中使用不同的数据库连接.首先断开主线程，然后在每个线程中重新连接，最后在主线程中重新连接，如下所示:

You need to use different connections to the database in your threads. First, disconnect the main thread, then reconnect in each thread, and finally reconnect in the main, like so:

ActiveRecord::Base.connection.disconnect!
(0..1).each do |index|
  threads << Thread.new do
    ActiveRecord::Base.establish_connection
    # ...
  end
end
ActiveRecord::Base.establish_connection

以这种方式进行测试还存在其他问题:您无法保证并发发生的点.ruby GIL 也无济于事.你应该使用 fork 而不是线程，或者使用 fork_break gem:https://github.com/remen/fork_break

There are other problems in testing that way: You have no guarantee of the point where concurrency happens. The ruby GIL will also not help. You should use forks instead of threads, or use the fork_break gem: https://github.com/remen/fork_break

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