Postgres：准备好的声明已经存在

Question

我在我的Rails API应用程序中使用Devise进行身份验证。 有时我在日志中看到以下错误：

ActiveRecord :: StatementInvalid：PGError：错误：准备好的语句“a3926”已经存在：UPDATE“users”SET“current_sign_in_at”= $ 1，“last_sign_in_at”= $ 2，“sign_in_count”= $ 3，“updated_at”= $ 4 WHERE“users”。 “id”= 12345

错误来自Devise：

  def update_tracked_fields!(request)
    old_current, new_current = self.current_sign_in_at, Time.now.utc
    self.last_sign_in_at     = old_current || new_current
    self.current_sign_in_at  = new_current

    old_current, new_current = self.current_sign_in_ip, request.remote_ip
    self.last_sign_in_ip     = old_current || new_current
    self.current_sign_in_ip  = new_current

    self.sign_in_count ||= 0
    self.sign_in_count += 1

    # error happens below
    save(validate: false) or raise "Devise trackable could not save #{inspect}." \
      "Please make sure a model using trackable can be saved at sign in."
  end

据我所知，当数据库连接的使用方式出现问题时，通常会发生此错误。 有什么我应该找的吗？

Answer 1

如果您正在使用一个提供进程的服务器（如独角兽），则需要为每个分叉进程创建一个连接。

如果是独角兽，请添加：

#config/unicorn.rb
before_fork do |server, worker|

  Signal.trap 'TERM' do
   puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
   Process.kill 'QUIT', Process.pid
 end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.connection.disconnect!
end

after_fork do |server, worker|

  Signal.trap 'TERM' do
    puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to sent QUIT'
  end

 defined?(ActiveRecord::Base) and
   ActiveRecord::Base.establish_connection(
     Rails.application.config.database_configuration[Rails.env]
   )

end