我遇到了我认为一定是并发问题。我正在使用乘客、rails 2.3.5、mongoid 1.9.2 和 mongo ruby​​ 驱动程序 1.0.9。我正在使用 jQuery 来请求从 MongoDB 中提取然后在浏览器中呈现的数据。一切都很好，直到我开始同时提出两个这样的请求。在模型中，这些是请求执行的方法:

Class Visit
  include Mongoid::Document
  ...
  def self.cancellations_and_visits_by_therapist_graph(clinic_id) 
    visits = collection.group("function(x){ return { resource_id : x.resource_id } }",
            {:clinic_id => clinic_id, :visit_date => { "$gte" => Time.now - 6.months, "$lte" => Time.now}}, 
            {:visits => 0, :cancel_no_shows => 0},
            'function(obj, count) {
              if (obj.visit_status == "NO SHOW" || obj.visits_status == "CANCELLED") {
                count.cancel_no_shows += 1;
              } else {
                count.visits += 1;
              }

            }')

    visits = visits.group_by {|g| g['resource_id']}

    Resource.any_in(:mysql_id => visits.keys).order_by([:last_name, :asc]).order_by([:first_name, :asc]).inject({ 'visits' => [], 'cancel_no_shows' => [], 'xlabels' => []}) do |formatted_visits, resource|
      formatted_visits['visits'] << visits[resource.mysql_id.to_f].first['visits']
      formatted_visits['cancel_no_shows'] << visits[resource.mysql_id.to_f].first['cancel_no_shows']
      formatted_visits['xlabels'] << resource.last_name + ", " + resource.first_name
      formatted_visits
    end
  end



  def self.total_visits_for_graph(practice_id)
    visits = collection.group("function(x) { return { clinic_id : x.clinic_id } }", 
                          {:practice_id => practice_id, :visit_status => 'COMPLETE', :visit_date => { "$gte" => Time.now - 6.months, "$lte" => Time.now}},
                          {:visits => 0}, "function(obj, count) { count.visits += 1; }")

    visits = visits.group_by {|g| g['clinic_id']}
    Clinic.any_in(:mysql_id => visits.keys).order_by([:name, :asc]).inject({ 'data' => [], 'xlabels' => []}) do |formatted_visits, clinic|
      formatted_visits['data'] << visits[clinic.mysql_id.to_f].first['visits']
      formatted_visits['xlabels'] << clinic.name
      formatted_visits
    end
  end
end

描述问题的最佳方式是 Mongo 的结果被传递给了错误的对象。我看了一个例子:

这是在我调用 CLinic.any_in 时返回的(它是其中一个组的结果):

{"group"=>{"$keyf"=>"function(x){ return { resource_id : x.resource_id } }", "cond"=>{:clinic_id=>101, :visit_date=>{"$gte"=>Tue Apr 20 15:34:37 +0800 2010, "$lte"=>Wed Oct 20 15:34:37 +0800 2010}}, "ns"=>"visits", "initial"=>{:visits=>0, :cancel_no_shows=>0}, "$reduce"=>"function(obj, count) {\n              if (obj.visit_status == \"NO SHOW\" || obj.visits_status == \"CANCELLED\") {\n                count.cancel_no_shows += 1;\n              } else {\n                count.visits += 1;\n              }\n\n            }"}}

这个(一个诊所对象)是由 collection.group 调用返回的:

{"_id"=>BSON::ObjectId('4cb7d72b3bc5457800ce2e6f'), "name"=>"Corona", "practice_id"=>39, "mysql_id"=>101}

与所有好的并发问题一样，结果是随机的，有时它运行良好，有时它会崩溃。我是 mongo 和 mongoid 的新手，所以我实际上不确定这是 mongoid 还是 mongo 驱动程序的问题，但我认为它与 Mongoid 有关。我包括了我用来在 Rails 中加载 Mongoid 的初始化程序。非常感谢任何想法，甚至只是额外的调试想法。

连接

mongoid_conf = YAML::load_file(Rails.root.join('config/mongoid.yml'))[Rails.env]

Mongoid.configure do |config|
  config.master = Mongo::Connection.new(mongoid_conf['host'], 27017, :pool_size => 5, :timeout => 5).db(mongoid_conf['database'])
end

最佳答案

我找到了解决这个问题的方法。实际上，它既不是 Mongo 司机也不是 Mongoid，而是乘客。当Passenger跨越rails进程时，它会 fork 当前实例，以便文件描述符(包括TCP描述符在应用程序实例之间共享)。这意味着 mongo 正在由同一个套接字写入和读取，这就是导致并发问题的原因。解决方案是让 mongo 在 fork 时重新连接。这是我找到的解决方案:

# Handle the creation of new processes by Phusion Passenger
if defined?(PhusionPassenger)
  PhusionPassenger.on_event(:starting_worker_process) do |forked|
    if forked
      # We're in smart spawning mode.

      # Reset the connection to MongoDB
      Mongoid.config.master.connection.close
      load File.join(RAILS_ROOT, 'config/initializers/mongoid_init.rb')
    else
      # We're in conservative spawning mode. We don't need to do anything.    
    end
  end
end

引用 http://groups.google.com/group/mongodb-user/browse_thread/thread/f31e2d23de38136a用于原始答案发布和讨论。

关于ruby-on-rails - Ruby Mongo 或 Mongoid 并发问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/3976407/