source: fedd/federation/local_segment.py @ 1553d27

#!/usr/local/bin/python

import sys, os
import re

import tempfile
import subprocess
import logging 
import time
import signal

import util

class local_segment:
    """
    Base class for starting a segments on a local testbed accessed directly
    through commands rather than ssh connections.  Code repository for
    executing commands with timeouts and other utility functions.
    """
    class cmd_timeout(RuntimeError): pass

    def __init__(self, log=None, keyfile=None, debug=False):
        """
        Parameters are a logger to use for updates, an unused key file, and a
        flag indicating that commands should not actually be carried out.
        """
        self.log = log or logging.getLogger(\
                'fedd.access.proxy_emulab_segment')
        self.certfile = keyfile
        self.debug = debug
        self.cmd_timeout = local_segment.cmd_timeout

    def copy_file(self, src, dest, size=1024):
        """
        Exceedingly simple file copy.
        """
        if not self.debug:
            util.copy_file(src, dest, size)
        else:
            self.log.debug("Copy %s to %s" % (src, dest))

    def cmd_with_timeout(self, cmd, wname=None, timeout=None):
        """
        Run a command.  If debug is set, the action
        is only logged.  Commands are run without stdin, to avoid stray
        SIGTTINs. If timeout is given and the command runs longer, a
        cmd_timeout exception is thrown.
        """

        try:
            dnull = open("/dev/null", "w")
        except EnvironmentError:
            self.log.debug("[cmd_with_timeout]: failed to open /dev/null " + \
                    "for redirect")
            dnull = Null

        self.log.debug("[cmd_with_timeout]: %s" % cmd)
        if not self.debug:
            if dnull:
                sub = subprocess.Popen(cmd, shell=True, stdout=dnull,
                        stderr=dnull, close_fds=True)
            else:
                sub = subprocess.Popen(cmd, shell=True, close_fds=True)
            if timeout:
                i = 0
                rv = sub.poll()
                while i < timeout:
                    if rv is not None: break
                    else:
                        time.sleep(1)
                        rv = sub.poll()
                        i += 1
                else:
                    self.log.debug("Process exceeded runtime: %s" % cmd)
                    os.kill(sub.pid, signal.SIGKILL)
                    raise self.cmd_timeout();
                return rv == 0
            else:
                return sub.wait() == 0
        else:
            if timeout == 0:
                self.log.debug("debug timeout raised on %s " % cmd)
                raise self.cmd_timeout()
            else:
                return True