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

[Royce Lv]

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'
> +
> +        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()