如何在使用ActiveRecord和多个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中实现多线程方法，以便我可以非常快速地创建/更新多条记录。

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

这是我的程序的概要。

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.

这给我一个错误

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

我尝试过：
-更改database.yaml并在那里增加池大小和超时。
-通过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。
我显然在这里没有这个概念。我该如何进行呢？

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

为防止多线程中的连接泄漏，您必须手动管理连接。您可以尝试：

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

的一个问题ActiveRecord :: Base.connection_pool.with_connection 是即使内部代码不需要它也总是准备连接。

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.

我们可以改进通过使用 ActiveRecord :: Base.connection_pool.release_connection ：

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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