如何在使用活动记录和多线程时管理打开和关闭数据库连接 [英] How to manage opening and closing database connections while working with activerecords and multiple threads

问题描述

我正在尝试在 rails 中实现一个多线程方法，以便我可以非常快速地创建/更新多个记录.

I am trying to implement a multithreaded method in rails such that I can create/update multiple records very quickly.

这是我的程序大纲.

ActiveRecord::Base.transaction do
  (1..10).each do |i|
    arr[i] = Thread.new {
       <some logic on obj>
       ...
       ...
       obj.save! 
    }
  end
  arr.each {|t| t.join}
end

这在我的日志中给了我警告.

This gives me warnings on my log.

DEPRECATION WARNING: Database connections will not be closed automatically, 
please close your database connection at the end of the thread by calling `close`
on your connection.

它给了我一个错误

could not obtain a database connection within 5 seconds (waited 5.059358 seconds). 
The max pool size is currently 5; consider increasing it.

我试过:- 更改 database.yaml 并增加池大小和超时.- 按以下方式修改现有代码.

I tried: - changing database.yaml and increasing the poolsize and timeout there. - modified the existing code in the following way.

   ActiveRecord::Base.connection_pool.clear_stale_cached_connections!
   begin
     ActiveRecord::Base.transaction do
        (1..10).each do |i|
          arr[i] = Thread.new {
             <some logic on obj>
             ...
             ...
             obj.save!
             ActiveRecord::Base.connection.close 
          }
        end
        arr.each {|t| t.join}
     end
   ensure
     ActiveRecord::Base.connection.close if ActiveRecord::Base.connection
     ActiveRecord::Base.clear_active_connections!
   end

我仍然收到相同的警告和错误.我显然在这里错过了这个概念.我该如何处理?

I am still getting the same warning and error. I am obviously missing the concept here. How do I proceed with this?

推荐答案

为了防止多线程中的连接泄漏，您必须手动管理连接.你可以试试:

To prevent connection leak in multi threads, you have to manage the connection manually. You can try:

Thread.new do
  ActiveRecord::Base.connection_pool.with_connection do
    # Do whatever
  end
end

ActiveRecord::Base.connection_pool.with_connection 的一个问题是它总是准备一个连接，即使里面的代码不需要它.

One problem of ActiveRecord::Base.connection_pool.with_connection is that it always prepare a connection even if the code inside does not need it.

我们可以通过使用ActiveRecord::Base.connection_pool.release_connection来改进它:

We can improve it a little bit by using ActiveRecord::Base.connection_pool.release_connection:

Thread.new do
  begin
    # Do whatever
  ensure
    ActiveRecord::Base.connection_pool.release_connection
  end
end

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