我正在尝试使用
python守护进程内部的paramiko执行ssh命令.
我正在为守护进程使用以下实现:
https://pypi.python.org/pypi/python-daemon/
当程序启动时,当paramiko尝试连接时,pycrypto会使用Bad文件描述符引发IOError.
如果我删除守护程序代码(只是取消注释最后一行并注释上面两个),则按预期建立ssh连接.
短测试程序的代码如下所示:
#!/usr/bin/env python2
from daemon import runner
import paramiko
class App():
def __init__(self):
self.stdin_path = '/dev/null'
self.stdout_path = '/dev/tty'
self.stderr_path = '/dev/tty'
self.pidfile_path = '/tmp/testdaemon.pid'
self.pidfile_timeout = 5
def run(self):
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.load_system_host_keys()
ssh.connect("hostname", username="username")
ssh.close()
app = App()
daemon_runner = runner.DaemonRunner(app)
daemon_runner.do_action()
#app.run()
跟踪看起来像这样:
Traceback (most recent call last):
File "./daemon-test.py", line 31, in <module>
daemon_runner.do_action()
File "/usr/lib/python2.7/site-packages/daemon/runner.py", line 189, in do_action
func(self)
File "/usr/lib/python2.7/site-packages/daemon/runner.py", line 134, in _start
self.app.run()
File "./daemon-test.py", line 22, in run
ssh.connect("hostname", username="username")
File "/usr/lib/python2.7/site-packages/paramiko/client.py", line 311, in connect
t.start_client()
File "/usr/lib/python2.7/site-packages/paramiko/transport.py", line 460, in start_client
Random.atfork()
File "/usr/lib/python2.7/site-packages/Crypto/Random/__init__.py", line 37, in atfork
_UserFriendlyRNG.reinit()
File "/usr/lib/python2.7/site-packages/Crypto/Random/_UserFriendlyRNG.py", line 224, in reinit
_get_singleton().reinit()
File "/usr/lib/python2.7/site-packages/Crypto/Random/_UserFriendlyRNG.py", line 171, in reinit
return _UserFriendlyRNG.reinit(self)
File "/usr/lib/python2.7/site-packages/Crypto/Random/_UserFriendlyRNG.py", line 99, in reinit
self._ec.reinit()
File "/usr/lib/python2.7/site-packages/Crypto/Random/_UserFriendlyRNG.py", line 62, in reinit
block = self._osrng.read(32*32)
File "/usr/lib/python2.7/site-packages/Crypto/Random/OSRNG/rng_base.py", line 76, in read
data = self._read(N)
File "/usr/lib/python2.7/site-packages/Crypto/Random/OSRNG/posix.py", line 65, in _read
d = self.__file.read(N - len(data))
IOError: [Errno 9] Bad file descriptor
我猜这与守护进程产生时的流重定向有关.我试图将它们全部设置为/ dev / tty甚至是普通文件,但没有任何效果.
当我用strace运行程序时,我可以看到某些东西试图关闭一个文件两次,那是我收到错误的时候.但我无法找出描述符实际指向哪个文件(strace显示的内存位置似乎没有在任何地方设置).
最佳答案 这是我实际遇到的一个已知问题(这是导致我这个问题的原因).基本上,它与UNIX守护进程的定义以及paramiko实现其随机数生成器(RNG)的方式有关.
如果您参考PEP 3143 – Standard daemon process library,成为正确守护程序的第一步是“关闭所有打开的文件描述符”.不幸的是,这会将文件描述符关闭到/ dev / urandom,这是在加密模块的RNG中使用的,后者又由paramiko使用.
目前有一些解决方法,但作者表示他目前没有时间去处理这个错误(虽然第一个链接中的最后一篇文章是作者,截至本文撰写时为8天).
> Daemonizing after importing paramiko breaks the random number
generator
> EAGAIN on file when using RNG after daemon fork
总之,如果在进程成为守护进程后导入paramiko,那么它应该按照需要工作,因为在守护进程关闭所有文件描述符之后将打开文件描述符.
用户@xraj也有一个hackish但聪明的解决方法,用于在守护进程时查找并保留文件描述符到/ dev / urandom(上面的第一个链接):
import os
from resource import getrlimit, RLIMIT_NOFILE
def files_preserve_by_path(*paths):
wanted=[]
for path in paths:
fd = os.open(path, os.O_RDONLY)
try:
wanted.append(os.fstat(fd)[1:3])
finally:
os.close(fd)
def fd_wanted(fd):
try:
return os.fstat(fd)[1:3] in wanted
except OSError:
return False
fd_max = getrlimit(RLIMIT_NOFILE)[1]
return [ fd for fd in xrange(fd_max) if fd_wanted(fd) ]
daemon_context.files_preserve = files_preserve_by_path('/dev/urandom')