title: spawn of Eventlet does not work. So strange
body: <p>**** hi,all</p>
  
  <p>i am using eventlet to implement a web crawler. My code is just like this</p>
  
  <pre><code>import eventlet
  
  
  urls = [
      "http://deeplearning.stanford.edu/wiki/index.php/UFLDL%E6%95%99%E7%A8%8B",
      "http://www.google.com.hk",
      "http://www.baidu.com",
  ]
  
  
  
  def fetch(url):
      print('entering fetch')
      body=urllib2.urlopen(url).read()
      print('body')
  
  
  pool = eventlet.GreenPool(100)
  for url in urls:
      pool.spawn(fetch,url)
      time.sleep(10)
  </code></pre>
  
  <p>but it outputs nothing  and it seems that fetch does not run at all</p>
  
  <p>BTW,pool.imap does works</p>
  
  <p>what happened? </p>
  
  <p>what i want to do is that：the urls are coming streamly ,i.e. one by one. just like this</p>
  
  <pre><code>While(True):
     url=getOneUrl() #get one url streamly
     pool.spawn(fetch,url) #fetch the url
  </code></pre>
  
  <p>but it does not work,either.</p>
  
  <p>thanks in advance....</p>