如何修复因打开而导致的死锁 [英] How to fix a deadlock caused by open

问题描述

我有一个死锁，但是我的程序中没有使用任何线程.另外，该错误仅每1000至1500个函数调用发生一次，因此很难查明和纠正.

I have is a deadlock, but I am not using any threads in my program. Plus, the error only happens about once every 1000 to 1500 function calls, making it very difficult to pinpoint and correct.

出现问题时，这里是完整的错误消息:

Here is the complete error message when the issue occurs:

/usr/lib/ruby/2.3.0/timeout.rb:95:in `join': No live threads left. Deadlock? (fatal)
    from /usr/lib/ruby/2.3.0/timeout.rb:95:in `ensure in block in timeout'
    from /usr/lib/ruby/2.3.0/timeout.rb:95:in `block in timeout'
    from /usr/lib/ruby/2.3.0/timeout.rb:101:in `timeout'
    from /usr/lib/ruby/2.3.0/net/http.rb:878:in `connect'
    from /usr/lib/ruby/2.3.0/net/http.rb:863:in `do_start'
    from /usr/lib/ruby/2.3.0/net/http.rb:852:in `start'
    from /usr/lib/ruby/2.3.0/open-uri.rb:319:in `open_http'
    from /usr/lib/ruby/2.3.0/open-uri.rb:737:in `buffer_open'
    from /usr/lib/ruby/2.3.0/open-uri.rb:212:in `block in open_loop'
    from /usr/lib/ruby/2.3.0/open-uri.rb:210:in `catch'
    from /usr/lib/ruby/2.3.0/open-uri.rb:210:in `open_loop'
    from /usr/lib/ruby/2.3.0/open-uri.rb:151:in `open_uri'
    from /usr/lib/ruby/2.3.0/open-uri.rb:717:in `open'
    from /usr/lib/ruby/2.3.0/open-uri.rb:35:in `open'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/sources/utils.rb:85:in `get_pic'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/mangafox/MF_download.rb:87:in `page_link'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/mangafox/MF_download.rb:116:in `chapter_link'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/mangafox/MF_download.rb:142:in `chapter'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/mangafox/MF_update.rb:57:in `block in MF_manga_missing_chapters'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/mangafox/MF_update.rb:45:in `reverse_each'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/mangafox/MF_update.rb:45:in `MF_manga_missing_chapters'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/mangafox/MF_update.rb:80:in `MF_update'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/sources/update.rb:5:in `update_manga'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/sources/update.rb:15:in `block in update_all'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/sources/update.rb:14:in `each'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/sources/update.rb:14:in `update_all'
    from /home/mat/travail_perso/RUBY/MangaScrapp_github/sources/update.rb:22:in `update'
    from ./MangaScrap.rb:28:in `<main>'

完整程序的链接为 https://github.com/Hellfire01/MangaScrap

该问题发生在使用open的三种不同方法上.这是这次崩溃的那一个:

The issue happens to the three different methods that use open. Here is the one that crashed this time:

# conect to link and download picture
def get_pic(link)
  safe_link = link.gsub(/[\[\]]/) { '%%%s' % $&.ord.to_s(16) }
  tries ||= 20
  begin
    page = open(safe_link, "User-Agent" => "Ruby/#{RUBY_VERSION}")
  rescue URI::InvalidURIError => error
    puts "Warning : bad url"
    puts link
    puts "message is : " + error.message
    return nil
  rescue => error
    if tries > 0
    tries -= 1
    sleep(0.2)
    retry
    else
      puts 'could not get picture ' + safe_link + ' after ' + $nb_tries.to_s + ' tries'
      puts "message is : " + error.message
      return nil
    end
  end
  sleep(0.2)
  return page
end

这是文件的链接: https://github .com/Hellfire01/MangaScrap/blob/master/sources/utils.rb

我想知道:

• 如何解决此错误?
• 如果无法解决此错误，我可以使用OpenUri的替代方法吗?

推荐答案

您不会在这里捕获所有异常.在rescue之后未指定任何内容时，表示您正在捕获的StandardError不在Exceptions层次结构的根本位置.

You're not catching all exceptions here. When nothing is specified after rescue, it means that you're catching StandardError which is not at the root of Exceptions' hierarchy.

如果您想确保捕获到所有异常并重试打开URL(或您想要的任何行为)，那么您要执行的操作是:

If you want to make sure you're catching all exceptions and retry opening a URL (or whatever behavior you'd like), what you want to do is:

rescue Exception => error

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