Re: [PATCH] KVM Test: add -w parameter in nc command in kvm_utils.py

[Michael Goldish <mgoldish@redhat.com>]

On 10/20/2010 12:18 PM, Feng Yang wrote:
> 
> ----- "Michael Goldish" <mgoldish@redhat.com> wrote:
> 
>> From: "Michael Goldish" <mgoldish@redhat.com>
>> To: "Feng Yang" <fyang@redhat.com>
>> Cc: autotest@test.kernel.org, kvm@vger.kernel.org
>> Sent: Wednesday, October 20, 2010 5:11:32 PM GMT +08:00 Beijing / Chongqing / Hong Kong / Urumqi
>> Subject: Re: [PATCH] KVM Test: add -w parameter in nc command in kvm_utils.py
>>
>> On 10/20/2010 08:55 AM, Feng Yang wrote:
>>> If a connection and stdin are idle for more than timeout seconds,
>>> then the connection is silently closed. withou this paramter,
>>> nc will listen forever for a connection. This may cause our test
>>> hang. redmine issue:
>>> http://redmine.englab.nay.redhat.com/issues/show/6947
>>> Add -w parameter should fix this issue.
>>>
>>> Signed-off-by: Feng Yang <fyang@redhat.com>
>>> ---
>>>  client/tests/kvm/kvm_utils.py |    2 +-
>>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/client/tests/kvm/kvm_utils.py
>> b/client/tests/kvm/kvm_utils.py
>>> index a51c857..526d38d 100644
>>> --- a/client/tests/kvm/kvm_utils.py
>>> +++ b/client/tests/kvm/kvm_utils.py
>>> @@ -733,7 +733,7 @@ def remote_login(client, host, port, username,
>> password, prompt, linesep="\n",
>>>      elif client == "telnet":
>>>          cmd = "telnet -l %s %s %s" % (username, host, port)
>>>      elif client == "nc":
>>> -        cmd = "nc %s %s" % (host, port)
>>> +        cmd = "nc %s %s -w %s" % (host, port, timeout)
>>>      else:
>>>          logging.error("Unknown remote shell client: %s" % client)
>>>          return
>>
>> I don't understand how remote_login() can stall here.
>> kvm_utils._remote_login() doesn't rely on nc's self-termination.  If
>> no
>> shell prompt is available after 10 seconds, nc is forcefully
>> terminated
>> and _remote_login() fails.  If it somehow stalls this might indicate
>> a
>> bug somewhere.
> It is really rarely reproduce. Only meet this issue when guest panic or core dump.
> nc stall. Do not know why it is not terminated after 10s.
> 
> I think -w parameter is helpful in this situation.
> If it does not cause other issue,  we'd better add -w in nc command.
> 
> Thanks for your command. What do you think?
> 
> Feng Yang

Adding -w 10 may cause trouble.  If a good functional session is idle
for more than 10 seconds during a test, it will be closed.  For example,
if you run a command that takes more than 10 seconds to complete, and
produces no output while it runs, the session will be closed.

Also, I doubt it'll solve the problem you've experienced.  As it is, the
code should (and usually does) properly handle the case of nc not
terminating.

If you manage to reproduce this again please save the log so I can have
a look at it.