文件在进程恶魔化时重新打开

Question

我在Sidekiq中找到了下一段与进程妖魔化相关的代码：

  files_to_reopen = []
  ObjectSpace.each_object(File) do |file|
    files_to_reopen << file unless file.closed?
  end

  ::Process.daemon(true, true)

  files_to_reopen.each do |file|
    begin
      file.reopen file.path, "a+"
      file.sync = true
    rescue ::Exception
    end
  end

  [$stdout, $stderr].each do |io|
    File.open(options[:logfile], 'ab') do |f|
      io.reopen(f)
    end
    io.sync = true
  end
  $stdin.reopen('/dev/null')

https://github.com/mperham/sidekiq/blob/master/lib/sidekiq/cli.rb#L191-L212

我不明白为什么我们在双叉上继承了文件描述符，为什么还要重新打开文件？是否存在某些特定案例可以做到这一点？ "Advanced Programming in the UNIX Environment" 书的作者，第 "Daemon Processes" 章，说仅关于关闭 不需要 文件描述符：

Unneeded file descriptors should be closed. This prevents the daemon from holding open any descriptors that it may have inherited from its parent (which could be a shell or some other process). We can use our open_max function (Figure 2.17) or the getrlimit function (Section 7.11) to determine the highest descriptor and close all descriptors up to that value.

Answer 1

我相信大部分代码都受到了 Unicorn 的启发。 Unicorn 的作者 Eric Wong 是 Ruby 世界的 Linux 先生，通常知道正确执行守护进程的所有技巧。

当然，从大局来看，不要守护进程。您应该使用合适的进程主管启动 Sidekiq：systemd、upstart、runit、foreman 等。

文件在进程恶魔化时重新打开

Files reopen on process demonization

ruby

sidekiq