ruby - 在多个线程中运行时出现 "Name or service not known (SocketError)"错误

Question

我制作了一个并行解析文本文件和下载数据的程序。在9个或更少的线程中运行下载方法时，程序没有错误。但是当在 10 个或更多线程中运行该方法时，程序会抛出“`initialize': getaddrinfo: Name or service not known (SocketError)”错误。我尝试了一些算法并行运行，但出现了同样的问题。我将发生“名称或服务未知”错误时传递给“打开”方法(open-uri)的 url 放入浏览器，并确认该 url 有效并收到正确的数据。这是部分代码。

jobs = []
aps = []
....
#jobs are pushed into jobs[]
....
max_thread = 15
loop do
  ary_threads = []
  max_thread.times do |i|
    break if jobs.size == 0
    job =  jobs.pop
    ary_threads << Thread.start {
      begin
        request(job[0],job[1]).each do |ap| #in "request" method, open(url)are called
            aps.push(ap)
        end
      end
    }
 end
 ary_threads.each { |th| th.join }
 break if jobs.size == 0
end

错误是

/usr/lib/ruby/1.9.1/net/http.rb:762:in `initialize': getaddrinfo: Name or service not known (SocketError)
from /usr/lib/ruby/1.9.1/net/http.rb:762:in `open'
from /usr/lib/ruby/1.9.1/net/http.rb:762:in `block in connect'
from /usr/lib/ruby/1.9.1/timeout.rb:54:in `timeout'
from /usr/lib/ruby/1.9.1/timeout.rb:99:in `timeout'
from /usr/lib/ruby/1.9.1/net/http.rb:762:in `connect'
from /usr/lib/ruby/1.9.1/net/http.rb:755:in `do_start'
from /usr/lib/ruby/1.9.1/net/http.rb:744:in `start'
from /usr/lib/ruby/1.9.1/open-uri.rb:306:in `open_http'
from /usr/lib/ruby/1.9.1/open-uri.rb:775:in `buffer_open'
from /usr/lib/ruby/1.9.1/open-uri.rb:203:in `block in open_loop'
from /usr/lib/ruby/1.9.1/open-uri.rb:201:in `catch'
from /usr/lib/ruby/1.9.1/open-uri.rb:201:in `open_loop'
from /usr/lib/ruby/1.9.1/open-uri.rb:146:in `open_uri'
from /var/lib/gems/1.9.1/gems/open-uri-cached-0.0.5/lib/open-uri/cached.rb:10:in `open_uri'
from /usr/lib/ruby/1.9.1/open-uri.rb:677:in `open'
from /usr/lib/ruby/1.9.1/open-uri.rb:33:in `open'
from Test1.rb:42:in `request'
from Test1.rb:77:in `block (3 levels) in <main>'

为什么会这样？有没有人遇到过类似的问题？请帮助我!

第一个问题后 3 小时，我找到了临时解决方案。如果我将“打开”方法夹在“开始~救援~重试~结束”的“请求”方法中，则第二次调用“打开”时不会发生错误。这是代码。

begin
    response = open(url)
rescue Exception
    puts url
    puts "retrying"
    retry
end

捕获异常并显示 url 和“重试”后，将永远不会显示 url 和“重试”，程序将正常运行:)但我仍然找不到导致此问题的原因。

Answer 1

我认为这可能是因为线程之间存在竞争条件。尝试以原子方式执行操作。放置互斥锁。

    @mutex = Mutex.new

    @mutex.syncronize do
      ...

      ary_threads << Thread.start {
       begin
        request(job[0],job[1]).each do |ap| #in "request" method, open(url)are called
          aps.push(ap)
        end
        end
      }

      ...
    end