找不到cherrypy /dev/urandom（或等效项）——错误

Question

我正在运行一个带有 Python 2.5.1 的cherrypy 3.2.0 服务器，它每隔几天就会在来自 UI 的任何指令上出现以下错误，直到它被杀死并重新启动：-

[29/Mar/2012:06:37:57] HTTP Traceback (most recent call last):
File "/usr/lib/python2.5/site-packages/CherryPy-3.2.0-py2.5.egg/cherrypy/_cprequest.py", line 636, in respond
File "/usr/lib/python2.5/site-packages/CherryPy-3.2.0-py2.5.egg/cherrypy/_cprequest.py", line 97, in run
File "/usr/lib/python2.5/site-packages/CherryPy-3.2.0-py2.5.egg/cherrypy/_cprequest.py", line 57, in __call__
File "/usr/lib/python2.5/site-packages/CherryPy-3.2.0-py2.5.egg/cherrypy/lib/sessions.py", line 757, in init
File "/usr/lib/python2.5/site-packages/CherryPy-3.2.0-py2.5.egg/cherrypy/lib/sessions.py", line 162, in __init__
File "/usr/lib/python2.5/site-packages/CherryPy-3.2.0-py2.5.egg/cherrypy/lib/sessions.py", line 190, in _regenerate
File "/usr/lib/python2.5/site-packages/CherryPy-3.2.0-py2.5.egg/cherrypy/lib/sessions.py", line 204, in generate_id
File "/usr/lib/python2.5/site-packages/CherryPy-3.2.0-py2.5.egg/cherrypy/_cpcompat.py", line 264, in random20
File "/usr/lib/python2.5/os.py", line 733, in urandom
NotImplementedError: /dev/urandom (or equivalent) not found

_cpcompat.py 有以下代码表明random.random 有一个后备，以防cherrypy 无法读取/dev/urandom，但似乎没有后备。

try:
    os.urandom(20)
    import binascii
    def random20():
        return binascii.hexlify(os.urandom(20)).decode('ascii')

except (AttributeError, NotImplementedError):
    import random
    # os.urandom not available until Python 2.4. Fall back to random.random.
    def random20(): 
        return sha('%s' % random.random()).hexdigest()

以下是来自os.py的代码sn-p，与上下文相关：-

if not _exists("urandom"):

    def urandom(n):
        """urandom(n) -> str

        Return a string of n random bytes suitable for cryptographic use.

        """
        try:
            _urandomfd = open("/dev/urandom", O_RDONLY)
        except (OSError, IOError):
            raise NotImplementedError("/dev/urandom (or equivalent) not found")
        bytes = ""
        while len(bytes) < n:
            bytes += read(_urandomfd, n - len(bytes))
        close(_urandomfd)
        return bytes

同时当cherrypy无法读取/dev/urandom时，以下代码sn-p工作正常：-

python -c "import os;fd = open('/dev/urandom', 'r');print fd.read(5);fd.close()"

我有两个问题：-

1. 为什么当我能够从 /dev/urandom 读取随机位时，cherrypy throwing not implemented 错误
2. 为什么os.py 提高NotImplementedError 时_cpcompact.py 不执行except 部分。

Answer 1

这也不是一个答案，但是，根据我的经验，这个 NotImplementedError 是错误的，但是当“太多文件”打开时出现错误在多处理后开始出现 进程开始抛出未捕获的异常，在子线程中永远悬空或子进程。

我会开始进一步调试堆栈，看看是否有进程抛出的隐藏或静默异常

这是我开始看到此错误时的堆栈跟踪示例

Exception in thread Plotter:
Traceback (most recent call last):
  File "threading.pyc", line 532, in __bootstrap_inner
  File "plotters/edge.pyc", line 459, in run
  AttributeError: 'error' object has no attribute 'error'

OSError: [Errno 24] Too many open files
  File "multiprocessing/connection.pyc", line 150, in Client
  File "multiprocessing/connection.pyc", line 370, in deliver_challenge
    None
  File "os.pyc", line 756, in urandom
NotImplementedError: /dev/urandom (or equivalent) not found

我的 AttributeError 最终产生了... /urandom not found imlp 错误

Answer 2

这不是答案，但也许您可以将一些调试代码放入os.py（我无法想象它会影响使用import os 的任何其他程序，但值得记住它的自定义）

if not _exists("urandom"):
    def urandom(n):
        """urandom(n) -> str

        Return a string of n random bytes suitable for cryptographic use.

        """
        try:
            _urandomfd = open("/dev/urandom", O_RDONLY)
        # debug changes
        except (OSError, IOError) as Err:
            import syslog
            syslog.syslog(repr(Err))
        # /debug
            raise NotImplementedError("/dev/urandom (or equivalent) not found")
        bytes = ""
        while len(bytes) < n:
            bytes += read(_urandomfd, n - len(bytes))
        close(_urandomfd)
        return bytes

希望这能准确地告诉您错误是什么。 （您当然可以用写入文件等替换 syslog）

Answer 3

如果您的系统尚未创建 /dev/random 和 /dev/urandom，可以使用以下命令创建它们：

mknod -m 644 /dev/random c 1 8

mknod -m 644 /dev/urandom c 1 9

chown root:root /dev/random /dev/urandom