Question

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/更新多个记录。

这是我的计划的大纲。

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

这会在我的日志上发出警告。

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.

我试过了： - 更改database.yaml并增加poolize和timeout。 - 以下列方式修改现有代码。

   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？

Answer 1

要防止多线程中的连接泄漏，您必须手动管理连接。你可以尝试：

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连接，即使内部的代码不需要它。

我们可以使用ActiveRecord::Base.connection_pool.release_connection：

稍微改善一下

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

Answer 2

如果要在N个线程中运行，请确保池中有N个连接

#  ActiveRecord::Base.connection_config
#  # => {pool: 5, timeout: 5000, database: "db/development.sqlite3", adapter: "sqlite3"}

否则您将能够从the pool获取连接。

如何在使用activerecords和多个线程时管理打开和关闭数据库连接

2 个答案: