Author juliadolgova
Recipients eryksun, juliadolgova, orsenthil, paul.moore, steve.dower, tim.golden, zach.ware
Date 2017-03-30.05:13:18
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May be I described the problem not clearly enough, because English is not my native language, so I try to explain once again.

In Windows there is an option "Do not use proxy server for address beginning with". I call this option <proxy bypass list>. This option is invented for Internet Explorer (IE) and is used by IE. It could be used by other applications and I think it's obvious that other applications must handle it same way as IE does. May be I'm wrong here, please dissuade me.

The problem is that IE only compares the hostname received with items in this list. And urllib also makes the reverse lookup and the forward lookup of the hostname and compares the results of those lookups with items in this list. To reproduce that you need to:
1. Run a proxy on your Windows or use any other proxy, that outputs requests coming from clients.
2. On Windows in "Browser settings" (IE settings) turn on the option "use proxy", set up the IP of your proxy, set the list "Do not use proxy server for address beginning with" to '' (without commas). ( - is the result of 'nslookup' at this time when I write this comment)
3. Make a request in IE to Then analyze the output of your proxy. You will see that the request to goes through proxy. 
4. Make a request to via urllib (run Analyze the output of your proxy. You will see that the request to bypasses proxy.

Be careful: there might be redirections when you make a request to If you see '' in proxy output and don't see '' it means that request to '' bypasses proxy.

This is the behavioral part of the problem which is attended by the performance decreasing, because the reverse lookup on some dns servers for some hostnames works slowly (up to 10 secs sometimes). May be the solution in my PR is not smart enough. But how can I make this issue go forward?
Date User Action Args
2017-03-30 05:13:19juliadolgovasetrecipients: + juliadolgova, paul.moore, orsenthil, tim.golden, zach.ware, eryksun, steve.dower
2017-03-30 05:13:19juliadolgovasetmessageid: <>
2017-03-30 05:13:19juliadolgovalinkissue29533 messages
2017-03-30 05:13:18juliadolgovacreate