Source code for Bcfg2.Utils

""" Miscellaneous useful utility functions, classes, etc., that are
used by both client and server.  Stuff that doesn't fit anywhere
else. """

import shlex
import fcntl
import logging
import threading
import subprocess
from Bcfg2.Compat import any  # pylint: disable=W0622

[docs]class ClassName(object): """ This very simple descriptor class exists only to get the name of the owner class. This is used because, for historical reasons, we expect every server plugin and every client tool to have a ``name`` attribute that is in almost all cases the same as the ``__class__.__name__`` attribute of the plugin object. This makes that more dynamic so that each plugin and tool isn't repeating its own name.""" def __get__(self, inst, owner): return owner.__name__
[docs]class PackedDigitRange(object): # pylint: disable=E0012,R0924 """ Representation of a set of integer ranges. A range is described by a comma-delimited string of integers and ranges, e.g.:: 1,10-12,15-20 Ranges are inclusive on both bounds, and may include 0. Negative numbers are not supported.""" def __init__(self, *ranges): """ May be instantiated in one of two ways:: PackedDigitRange(<comma-delimited list of ranges>) Or:: PackedDigitRange(<int_or_range>[, <int_or_range>[, ...]]) E.g., both of the following are valid:: PackedDigitRange("1-5,7, 10-12") PackedDigitRange("1-5", 7, "10-12") """ self.ranges = [] self.ints = [] self.str = ",".join(str(r) for r in ranges) if len(ranges) == 1 and "," in ranges[0]: ranges = ranges[0].split(",") for item in ranges: item = str(item).strip() if item.endswith("-"): self.ranges.append((int(item[:-1]), None)) elif '-' in str(item): self.ranges.append(tuple(int(x) for x in item.split('-'))) else: self.ints.append(int(item))
[docs] def includes(self, other): """ Return True if ``other`` is included in this range. Functionally equivalent to ``other in range``, which should be used instead. """ return other in self
def __contains__(self, other): other = int(other) if other in self.ints: return True return any((end is None and other >= start) or (end is not None and other >= start and other <= end) for start, end in self.ranges) def __repr__(self): return "%s:%s" % (self.__class__.__name__, str(self)) def __str__(self): return "[%s]" % self.str
[docs]def locked(fd): """ Acquire a lock on a file. :param fd: The file descriptor to lock :type fd: int :returns: bool - True if the file is already locked, False otherwise """ try: fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB) except IOError: return True return False
[docs]class ExecutorResult(object): """ Returned as the result of a call to :func:``. The result can be accessed via the instance variables, documented below, as a boolean (which is equivalent to :attr:`Bcfg2.Utils.ExecutorResult.success`), or as a tuple, which, for backwards compatibility, is equivalent to ``(result.retval, result.stdout.splitlines())``.""" def __init__(self, stdout, stderr, retval): #: The output of the command if isinstance(stdout, str): self.stdout = stdout else: self.stdout = stdout.decode('utf-8') #: The error produced by the command if isinstance(stdout, str): self.stderr = stderr else: self.stderr = stderr.decode('utf-8') #: The return value of the command. self.retval = retval #: Whether or not the command was successful. If the #: ExecutorResult is used as a boolean, ``success`` is #: returned. self.success = retval == 0 #: A friendly error message self.error = None if self.retval: if self.stderr: self.error = "%s (rv: %s)" % (self.stderr, self.retval) elif self.stdout: self.error = "%s (rv: %s)" % (self.stdout, self.retval) else: self.error = "No output or error; return value %s" % \ self.retval def __repr__(self): if self.error: return "Errored command result: %s" % self.error elif self.stdout: return "Successful command result: %s" % self.stdout else: return "Successful command result: No output" def __getitem__(self, idx): """ This provides compatibility with the old Executor, which returned a tuple of (return value, stdout split by lines). """ return (self.retval, self.stdout.splitlines())[idx] def __len__(self): """ This provides compatibility with the old Executor, which returned a tuple of (return value, stdout split by lines). """ return 2 def __delitem__(self, _): raise TypeError("'%s' object doesn't support item deletion" % self.__class__.__name__) def __setitem__(self, idx, val): raise TypeError("'%s' object does not support item assignment" % self.__class__.__name__) def __nonzero__(self): return self.__bool__() def __bool__(self): return self.success
[docs]class Executor(object): """ A convenient way to run external commands with :class:`subprocess.Popen` """ def __init__(self, timeout=None): """ :param timeout: Set a default timeout for all commands run by this Executor object :type timeout: float """ self.logger = logging.getLogger(self.__class__.__name__) self.timeout = timeout def _timeout(self, proc): """ A function suitable for passing to :class:`threading.Timer` that kills the given process. :param proc: The process to kill upon timeout. :type proc: subprocess.Popen :returns: None """ if proc.poll() is None: try: proc.kill() self.logger.warning("Process exceeeded timeout, killing") except OSError: pass
[docs] def run(self, command, inputdata=None, shell=False, timeout=None): """ Run a command, given as a list, optionally giving it the specified input data. :param command: The command to run, as a list (preferred) or as a string. See :class:`subprocess.Popen` for details. :type command: list or string :param inputdata: Data to pass to the command on stdin :type inputdata: string :param shell: Run the given command in a shell (not recommended) :type shell: bool :param timeout: Kill the command if it runs longer than this many seconds. Set to 0 or -1 to explicitly override a default timeout. :type timeout: float :returns: :class:`Bcfg2.Utils.ExecutorResult` """ if isinstance(command, str): cmdstr = command if not shell: command = shlex.split(cmdstr) else: cmdstr = " ".join(command) self.logger.debug("Running: %s" % cmdstr) try: proc = subprocess.Popen(command, shell=shell, bufsize=16384, close_fds=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE) except OSError: return ExecutorResult('', 'No such command: %s' % cmdstr, 127) if timeout is None: timeout = self.timeout if timeout is not None: timer = threading.Timer(float(timeout), self._timeout, [proc]) timer.start() try: if inputdata: for line in inputdata.splitlines(): self.logger.debug('> %s' % line) (stdout, stderr) = proc.communicate(input=inputdata) # py3k fixes if not isinstance(stdout, str): stdout = stdout.decode('utf-8') # pylint: disable=E1103 if not isinstance(stderr, str): stderr = stderr.decode('utf-8') # pylint: disable=E1103 for line in stdout.splitlines(): # pylint: disable=E1103 self.logger.debug('< %s' % line) for line in stderr.splitlines(): # pylint: disable=E1103 return ExecutorResult(stdout, stderr, proc.wait()) finally: if timeout is not None: timer.cancel()