#encoding=utf-8

'''

在python里调用子进程要防止子进程长时间运行,

如果处理一个web请求的时候需要调用子进程取结果,

一般可以超过一定时间后直接kill掉子进程

Popen一般会很快，不会阻塞太久，

但子进程的stdout.read方法是同步且不可以设置超时的

这样用gevent spawn一个协程开子进程read的话，

read会卡住整个协程，让所有的协程无法运行

而且用gevent.Timeout去设置超时也不管用

这就需要用到gevent.socket.wait_read了，

该方法可以等待一个文件描述符可读，

且等待可以设置超时参数，或用gevent.Timeout,

greenlet.get(timeout)来设置超时

refs:

https://bitbucket.org/denis/gevent/src/tip/examples/geventsendfile.py

'''

from subprocess import Popen, PIPE

from gevent.socket import wait_read

from sys import exc_info

try:

from errno import EBADF

except ImportError:

EBADF = 9

def runwithtimeout(cmd, timeout):

process = Popen(cmd,shell=True, stdout=PIPE, stderr=PIPE,

close_fds=True)

stdout, stderr = None, None

try:

stdout = read(process.stdout, timeout)

stderr = read(process.stderr, timeout)

except Exception, ex:

print 'popen timeout:', cmd

finally:

process.kill()

return stdout, stderr

def read(fromfile, timeout):

while True:

try:

wait_read(fromfile.fileno(), timeout)

return fromfile.read()

except:

ex = exc_info()[1]

if ex.args[0] == EBADF:

return ''

raise

if __name__ == '__main__':

from gevent import spawn

from traceback import format_exception

cmd = 'curl -I --connect-timeout %s -m %s %s ' \

% (5, 5, '202.99.160.68')

task = spawn(runwithtimeout, cmd, 10)

try:

print ''.join(task.get())

except:

type, value, tb = exc_info()

print ''.join(format_exception(type,value, tb))