[Kimchi-devel] [PATCH V1] add a synchronous function with timeout to execute command

[Sheldon]

On 01/10/2014 04:16 PM, Royce Lv wrote:
> On 2014年01月10日 09:00, shaohef at linux.vnet.ibm.com wrote:
>> From: ShaoHe Feng <shaohef at linux.vnet.ibm.com>
>>
>> We need a common function to execute shell command.
>> We also need timeout when execute shell command.
>>
>> A threading.Timer is used to send signal.SIGKILL to kill the command
>> when timeout.
>>
>> Signed-off-by: Royce Lv <lvroyce at linux.vnet.ibm.com>
>> Signed-off-by: ShaoHe Feng <shaohef at linux.vnet.ibm.com>
>> ---
>>   src/kimchi/utils.py | 39 +++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 39 insertions(+)
>>
>> diff --git a/src/kimchi/utils.py b/src/kimchi/utils.py
>> index af245c6..94097ad 100644
>> --- a/src/kimchi/utils.py
>> +++ b/src/kimchi/utils.py
>> @@ -23,6 +23,7 @@
>>
>>   import cherrypy
>>   import os
>> +import subprocess
>>   import urllib2
>>
>>
>> @@ -30,6 +31,7 @@ from cherrypy.lib.reprconf import Parser
>>
>>
>>   from kimchi import config
>> +from threading import Timer
>>
>>
>>   kimchi_log = cherrypy.log.error_log
>> @@ -96,3 +98,40 @@ def check_url_path(path):
>>           return False
>>
>>       return True
>> +
>> +
>> +def run_command(cmd, timeout=None):
>> +    def kill_proc(proc, timeout_flag):
>> +        timeout_flag[0] = True
>> +        proc.kill()
>> +
>> +    proc = None
>> +    timer = None
>> +    timeout_flag = [False]
>> +
>> +    try:
>> +        proc = subprocess.Popen(cmd, stdout=subprocess.PIPE,
>> +                                stderr=subprocess.PIPE)
>> +        if timeout is not None:
>> +            timer = Timer(timeout, kill_proc, [proc, timeout_flag])
>> +            timer.start()
> I like the idea of using timer, I think the only thing we need to take 
> care is check timeout happens and report a specific error.
> Or when we kill the proc and it is blocked, the proc.communicate() 
> error will not be 'timeout happens'

when we kill the proc, the proc.returncode will be -9 and 
timeout_flag[0] is True.

so we can log the timeout

if proc.returncode == -9 and timeout_flag[0] is True:
      kimchi_log.error("process is killed by signal.SIGKILL for timeout 
%s seconds", timeout)

or raise a TimeoutError:
we can define a new Exception TimeoutError.
if proc.returncode == -9 and timeout_flag[0] is True:
      raise TimeoutError("process is killed by signal.SIGKILL for 
timeout %s seconds" % timeout)

>> +
>> +        out, error = proc.communicate()
>> +        kimchi_log.debug("Run command '%s'", " ".join(cmd))
>> +
>> +        if out or error:
>> +            kimchi_log.debug("out:\n %s\nerror:\n %s", out, error)
>> +
>> +        return out, error, proc.returncode, timeout_flag[0]
>> +    except Exception as e:
>> +        msg = "Failed to run command: %s." % " ".join(cmd)
>> +        msg = msg if proc is None else msg + "\n  error code: %s."
>> +        kimchi_log.error("%s\n  %s", msg, e)
>> +
>> +        if proc:
>> +            return out, error, proc.returncode, timeout_flag[0]
>> +        else:
>> +            return None, None, None, timeout_flag[0]
>> +    finally:
>> +        if timer and not timeout_flag[0]:
>> +            timer.cancel()
>
>
>


-- 
Thanks and best regards!

Sheldon Feng(冯少合)<shaohef at linux.vnet.ibm.com>
IBM Linux Technology Center

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