Synnefo » snf-ganeti

#

#

# Copyright (C) 2006, 2007 Google Inc.

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful, but

# WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Module dealing with command line parsing"""

import sys

import textwrap

import os.path

import copy

import time

import logging

from cStringIO import StringIO

from ganeti import utils

from ganeti import errors

from ganeti import constants

from ganeti import opcodes

from ganeti import luxi

from ganeti import ssconf

from ganeti import rpc

from optparse import (OptionParser, TitledHelpFormatter,

                      Option, OptionValueError)

__all__ = [

  # Command line options

  "CONFIRM_OPT",

  "DEBUG_OPT",

  "DEBUG_SIMERR_OPT",

  "DISK_TEMPLATE_OPT",

  "FIELDS_OPT",

  "FILESTORE_DIR_OPT",

  "FILESTORE_DRIVER_OPT",

  "FORCE_OPT",

  "NOHDR_OPT",

  "NONICS_OPT",

  "NWSYNC_OPT",

  "SEP_OPT",

  "SUBMIT_OPT",

  "SYNC_OPT",

  "TAG_SRC_OPT",

  "USEUNITS_OPT",

  "VERBOSE_OPT",

  # Generic functions for CLI programs

  "GenericMain",

  "GetClient",

  "GetOnlineNodes",

  "JobExecutor",

  "JobSubmittedException",

  "ParseTimespec",

  "SubmitOpCode",

  "SubmitOrSend",

  "UsesRPC",

  # Formatting functions

  "ToStderr", "ToStdout",

  "FormatError",

  "GenerateTable",

  "AskUser",

  "FormatTimestamp",

  # Tags functions

  "ListTags",

  "AddTags",

  "RemoveTags",

  # command line options support infrastructure

  "ARGS_MANY_INSTANCES",

  "ARGS_MANY_NODES",

  "ARGS_NONE",

  "ARGS_ONE_INSTANCE",

  "ARGS_ONE_NODE",

  "ArgChoice",

  "ArgCommand",

  "ArgFile",

  "ArgHost",

  "ArgInstance",

  "ArgJobId",

  "ArgNode",

  "ArgSuggest",

  "ArgUnknown",

  "OPT_COMPL_INST_ADD_NODES",

  "OPT_COMPL_MANY_NODES",

  "OPT_COMPL_ONE_IALLOCATOR",

  "OPT_COMPL_ONE_INSTANCE",

  "OPT_COMPL_ONE_NODE",

  "OPT_COMPL_ONE_OS",

  "cli_option",

  "SplitNodeOption",

  ]

NO_PREFIX = "no_"

UN_PREFIX = "-"

class _Argument:

  def __init__(self, min=0, max=None):

    self.min = min

    self.max = max

  def __repr__(self):

    return ("<%s min=%s max=%s>" %

            (self.__class__.__name__, self.min, self.max))

class ArgSuggest(_Argument):

  """Suggesting argument.

  Value can be any of the ones passed to the constructor.

  """

  def __init__(self, min=0, max=None, choices=None):

    _Argument.__init__(self, min=min, max=max)

    self.choices = choices

  def __repr__(self):

    return ("<%s min=%s max=%s choices=%r>" %

            (self.__class__.__name__, self.min, self.max, self.choices))

class ArgChoice(ArgSuggest):

  """Choice argument.

  Value can be any of the ones passed to the constructor. Like L{ArgSuggest},

  but value must be one of the choices.

  """

class ArgUnknown(_Argument):

  """Unknown argument to program (e.g. determined at runtime).

  """

class ArgInstance(_Argument):

  """Instances argument.

  """

class ArgNode(_Argument):

  """Node argument.

  """

class ArgJobId(_Argument):

  """Job ID argument.

  """

class ArgFile(_Argument):

  """File path argument.

  """

class ArgCommand(_Argument):

  """Command argument.

  """

class ArgHost(_Argument):

  """Host argument.

  """

ARGS_NONE = []

ARGS_MANY_INSTANCES = [ArgInstance()]

ARGS_MANY_NODES = [ArgNode()]

ARGS_ONE_INSTANCE = [ArgInstance(min=1, max=1)]

ARGS_ONE_NODE = [ArgNode(min=1, max=1)]

def _ExtractTagsObject(opts, args):

  """Extract the tag type object.

  Note that this function will modify its args parameter.

  """

  if not hasattr(opts, "tag_type"):

    raise errors.ProgrammerError("tag_type not passed to _ExtractTagsObject")

  kind = opts.tag_type

  if kind == constants.TAG_CLUSTER:

    retval = kind, kind

  elif kind == constants.TAG_NODE or kind == constants.TAG_INSTANCE:

    if not args:

      raise errors.OpPrereqError("no arguments passed to the command")

    name = args.pop(0)

    retval = kind, name

  else:

    raise errors.ProgrammerError("Unhandled tag type '%s'" % kind)

  return retval

def _ExtendTags(opts, args):

  """Extend the args if a source file has been given.

  This function will extend the tags with the contents of the file

  passed in the 'tags_source' attribute of the opts parameter. A file

  named '-' will be replaced by stdin.

  """

  fname = opts.tags_source

  if fname is None:

    return

  if fname == "-":

    new_fh = sys.stdin

  else:

    new_fh = open(fname, "r")

  new_data = []

  try:

    # we don't use the nice 'new_data = [line.strip() for line in fh]'

    # because of python bug 1633941

    while True:

      line = new_fh.readline()

      if not line:

        break

      new_data.append(line.strip())

  finally:

    new_fh.close()

  args.extend(new_data)

def ListTags(opts, args):

  """List the tags on a given object.

  This is a generic implementation that knows how to deal with all

  three cases of tag objects (cluster, node, instance). The opts

  argument is expected to contain a tag_type field denoting what

  object type we work on.

  """

  kind, name = _ExtractTagsObject(opts, args)

  op = opcodes.OpGetTags(kind=kind, name=name)

  result = SubmitOpCode(op)

  result = list(result)

  result.sort()

  for tag in result:

    ToStdout(tag)

def AddTags(opts, args):

  """Add tags on a given object.

  This is a generic implementation that knows how to deal with all

  three cases of tag objects (cluster, node, instance). The opts

  argument is expected to contain a tag_type field denoting what

  object type we work on.

  """

  kind, name = _ExtractTagsObject(opts, args)

  _ExtendTags(opts, args)

  if not args:

    raise errors.OpPrereqError("No tags to be added")

  op = opcodes.OpAddTags(kind=kind, name=name, tags=args)

  SubmitOpCode(op)

def RemoveTags(opts, args):

  """Remove tags from a given object.

  This is a generic implementation that knows how to deal with all

  three cases of tag objects (cluster, node, instance). The opts

  argument is expected to contain a tag_type field denoting what

  object type we work on.

  """

  kind, name = _ExtractTagsObject(opts, args)

  _ExtendTags(opts, args)

  if not args:

    raise errors.OpPrereqError("No tags to be removed")

  op = opcodes.OpDelTags(kind=kind, name=name, tags=args)

  SubmitOpCode(op)

def check_unit(option, opt, value):

  """OptParsers custom converter for units.

  """

  try:

    return utils.ParseUnit(value)

  except errors.UnitParseError, err:

    raise OptionValueError("option %s: %s" % (opt, err))

def _SplitKeyVal(opt, data):

  """Convert a KeyVal string into a dict.

  This function will convert a key=val[,...] string into a dict. Empty

  values will be converted specially: keys which have the prefix 'no_'

  will have the value=False and the prefix stripped, the others will

  have value=True.

  @type opt: string

  @param opt: a string holding the option name for which we process the

      data, used in building error messages

  @type data: string

  @param data: a string of the format key=val,key=val,...

  @rtype: dict

  @return: {key=val, key=val}

  @raises errors.ParameterError: if there are duplicate keys

  """

  kv_dict = {}

  if data:

    for elem in data.split(","):

      if "=" in elem:

        key, val = elem.split("=", 1)

      else:

        if elem.startswith(NO_PREFIX):

          key, val = elem[len(NO_PREFIX):], False

        elif elem.startswith(UN_PREFIX):

          key, val = elem[len(UN_PREFIX):], None

        else:

          key, val = elem, True

      if key in kv_dict:

        raise errors.ParameterError("Duplicate key '%s' in option %s" %

                                    (key, opt))

      kv_dict[key] = val

  return kv_dict

def check_ident_key_val(option, opt, value):

  """Custom parser for ident:key=val,key=val options.

  This will store the parsed values as a tuple (ident, {key: val}). As such,

  multiple uses of this option via action=append is possible.

  """

  if ":" not in value:

    ident, rest = value, ''

  else:

    ident, rest = value.split(":", 1)

  if ident.startswith(NO_PREFIX):

    if rest:

      msg = "Cannot pass options when removing parameter groups: %s" % value

      raise errors.ParameterError(msg)

    retval = (ident[len(NO_PREFIX):], False)

  elif ident.startswith(UN_PREFIX):

    if rest:

      msg = "Cannot pass options when removing parameter groups: %s" % value

      raise errors.ParameterError(msg)

    retval = (ident[len(UN_PREFIX):], None)

  else:

    kv_dict = _SplitKeyVal(opt, rest)

    retval = (ident, kv_dict)

  return retval

def check_key_val(option, opt, value):

  """Custom parser class for key=val,key=val options.

  This will store the parsed values as a dict {key: val}.

  """

  return _SplitKeyVal(opt, value)

# completion_suggestion is normally a list. Using numeric values not evaluating

# to False for dynamic completion.

(OPT_COMPL_MANY_NODES,

 OPT_COMPL_ONE_NODE,

 OPT_COMPL_ONE_INSTANCE,

 OPT_COMPL_ONE_OS,

 OPT_COMPL_ONE_IALLOCATOR,

 OPT_COMPL_INST_ADD_NODES) = range(100, 106)

OPT_COMPL_ALL = frozenset([

  OPT_COMPL_MANY_NODES,

  OPT_COMPL_ONE_NODE,

  OPT_COMPL_ONE_INSTANCE,

  OPT_COMPL_ONE_OS,

  OPT_COMPL_ONE_IALLOCATOR,

  OPT_COMPL_INST_ADD_NODES,

  ])

class CliOption(Option):

  """Custom option class for optparse.

  """

  ATTRS = Option.ATTRS + [

    "completion_suggest",

    ]

  TYPES = Option.TYPES + (

    "identkeyval",

    "keyval",

    "unit",

    )

  TYPE_CHECKER = Option.TYPE_CHECKER.copy()

  TYPE_CHECKER["identkeyval"] = check_ident_key_val

  TYPE_CHECKER["keyval"] = check_key_val

  TYPE_CHECKER["unit"] = check_unit

# optparse.py sets make_option, so we do it for our own option class, too

cli_option = CliOption

DEBUG_OPT = cli_option("-d", "--debug", default=False,

                       action="store_true",

                       help="Turn debugging on")

NOHDR_OPT = cli_option("--no-headers", default=False,

                       action="store_true", dest="no_headers",

                       help="Don't display column headers")

SEP_OPT = cli_option("--separator", default=None,

                     action="store", dest="separator",

                     help=("Separator between output fields"

                           " (defaults to one space)"))

USEUNITS_OPT = cli_option("--units", default=None,

                          dest="units", choices=('h', 'm', 'g', 't'),

                          help="Specify units for output (one of hmgt)")

FIELDS_OPT = cli_option("-o", "--output", dest="output", action="store",

                        type="string", metavar="FIELDS",

                        help="Comma separated list of output fields")

FORCE_OPT = cli_option("-f", "--force", dest="force", action="store_true",

                       default=False, help="Force the operation")

CONFIRM_OPT = cli_option("--yes", dest="confirm", action="store_true",

                         default=False, help="Do not require confirmation")

TAG_SRC_OPT = cli_option("--from", dest="tags_source",

                         default=None, help="File with tag names")

SUBMIT_OPT = cli_option("--submit", dest="submit_only",

                        default=False, action="store_true",

                        help=("Submit the job and return the job ID, but"

                              " don't wait for the job to finish"))

SYNC_OPT = cli_option("--sync", dest="do_locking",

                      default=False, action="store_true",

                      help=("Grab locks while doing the queries"

                            " in order to ensure more consistent results"))

_DRY_RUN_OPT = cli_option("--dry-run", default=False,

                          action="store_true",

                          help=("Do not execute the operation, just run the"

                                " check steps and verify it it could be"

                                " executed"))

VERBOSE_OPT = cli_option("-v", "--verbose", default=False,

                         action="store_true",

                         help="Increase the verbosity of the operation")

DEBUG_SIMERR_OPT = cli_option("--debug-simulate-errors", default=False,

                              action="store_true", dest="simulate_errors",

                              help="Debugging option that makes the operation"

                              " treat most runtime checks as failed")

NWSYNC_OPT = cli_option("--no-wait-for-sync", dest="wait_for_sync",

                        default=True, action="store_false",

                        help="Don't wait for sync (DANGEROUS!)")

DISK_TEMPLATE_OPT = cli_option("-t", "--disk-template", dest="disk_template",

                               help="Custom disk setup (diskless, file,"

                               " plain or drbd)",

                               default=None, metavar="TEMPL",

                               choices=list(constants.DISK_TEMPLATES))

NONICS_OPT = cli_option("--no-nics", default=False, action="store_true",

                        help="Do not create any network cards for"

                        " the instance")

FILESTORE_DIR_OPT = cli_option("--file-storage-dir", dest="file_storage_dir",

                               help="Relative path under default cluster-wide"

                               " file storage dir to store file-based disks",

                               default=None, metavar="<DIR>")

FILESTORE_DRIVER_OPT = cli_option("--file-driver", dest="file_driver",

                                  help="Driver to use for image files",

                                  default="loop", metavar="<DRIVER>",

                                  choices=list(constants.FILE_DRIVER))

def _ParseArgs(argv, commands, aliases):

  """Parser for the command line arguments.

  This function parses the arguments and returns the function which

  must be executed together with its (modified) arguments.

  @param argv: the command line

  @param commands: dictionary with special contents, see the design

      doc for cmdline handling

  @param aliases: dictionary with command aliases {'alias': 'target, ...}

  """

  if len(argv) == 0:

    binary = "<command>"

  else:

    binary = argv[0].split("/")[-1]

  if len(argv) > 1 and argv[1] == "--version":

    ToStdout("%s (ganeti) %s", binary, constants.RELEASE_VERSION)

    # Quit right away. That way we don't have to care about this special

    # argument. optparse.py does it the same.

    sys.exit(0)

  if len(argv) < 2 or not (argv[1] in commands or

                           argv[1] in aliases):

    # let's do a nice thing

    sortedcmds = commands.keys()

    sortedcmds.sort()

    ToStdout("Usage: %s {command} [options...] [argument...]", binary)

    ToStdout("%s <command> --help to see details, or man %s", binary, binary)

    ToStdout("")

    # compute the max line length for cmd + usage

    mlen = max([len(" %s" % cmd) for cmd in commands])

    mlen = min(60, mlen) # should not get here...

    # and format a nice command list

    ToStdout("Commands:")

    for cmd in sortedcmds:

      cmdstr = " %s" % (cmd,)

      help_text = commands[cmd][4]

      help_lines = textwrap.wrap(help_text, 79 - 3 - mlen)

      ToStdout("%-*s - %s", mlen, cmdstr, help_lines.pop(0))

      for line in help_lines:

        ToStdout("%-*s   %s", mlen, "", line)

    ToStdout("")

    return None, None, None

  # get command, unalias it, and look it up in commands

  cmd = argv.pop(1)

  if cmd in aliases:

    if cmd in commands:

      raise errors.ProgrammerError("Alias '%s' overrides an existing"

                                   " command" % cmd)

    if aliases[cmd] not in commands:

      raise errors.ProgrammerError("Alias '%s' maps to non-existing"

                                   " command '%s'" % (cmd, aliases[cmd]))

    cmd = aliases[cmd]

  func, args_def, parser_opts, usage, description = commands[cmd]

  parser = OptionParser(option_list=parser_opts + [_DRY_RUN_OPT],

                        description=description,

                        formatter=TitledHelpFormatter(),

                        usage="%%prog %s %s" % (cmd, usage))

  parser.disable_interspersed_args()

  options, args = parser.parse_args()

  if not _CheckArguments(cmd, args_def, args):

    return None, None, None

  return func, options, args

def _CheckArguments(cmd, args_def, args):

  """Verifies the arguments using the argument definition.

  Algorithm:

    1. Abort with error if values specified by user but none expected.

    1. For each argument in definition

      1. Keep running count of minimum number of values (min_count)

      1. Keep running count of maximum number of values (max_count)

      1. If it has an unlimited number of values

        1. Abort with error if it's not the last argument in the definition

    1. If last argument has limited number of values

      1. Abort with error if number of values doesn't match or is too large

    1. Abort with error if user didn't pass enough values (min_count)

  """

  if args and not args_def:

    ToStderr("Error: Command %s expects no arguments", cmd)

    return False

  min_count = None

  max_count = None

  check_max = None

  last_idx = len(args_def) - 1

  for idx, arg in enumerate(args_def):

    if min_count is None:

      min_count = arg.min

    elif arg.min is not None:

      min_count += arg.min

    if max_count is None:

      max_count = arg.max

    elif arg.max is not None:

      max_count += arg.max

    if idx == last_idx:

      check_max = (arg.max is not None)

    elif arg.max is None:

      raise errors.ProgrammerError("Only the last argument can have max=None")

  if check_max:

    # Command with exact number of arguments

    if (min_count is not None and max_count is not None and

        min_count == max_count and len(args) != min_count):

      ToStderr("Error: Command %s expects %d argument(s)", cmd, min_count)

      return False

    # Command with limited number of arguments

    if max_count is not None and len(args) > max_count:

      ToStderr("Error: Command %s expects only %d argument(s)",

               cmd, max_count)

      return False

  # Command with some required arguments

  if min_count is not None and len(args) < min_count:

    ToStderr("Error: Command %s expects at least %d argument(s)",

             cmd, min_count)

    return False

  return True

def SplitNodeOption(value):

  """Splits the value of a --node option.

  """

  if value and ':' in value:

    return value.split(':', 1)

  else:

    return (value, None)

def UsesRPC(fn):

  def wrapper(*args, **kwargs):

    rpc.Init()

    try:

      return fn(*args, **kwargs)

    finally:

      rpc.Shutdown()

  return wrapper

def AskUser(text, choices=None):

  """Ask the user a question.

  @param text: the question to ask

  @param choices: list with elements tuples (input_char, return_value,

      description); if not given, it will default to: [('y', True,

      'Perform the operation'), ('n', False, 'Do no do the operation')];

      note that the '?' char is reserved for help

  @return: one of the return values from the choices list; if input is

      not possible (i.e. not running with a tty, we return the last

      entry from the list

  """

  if choices is None:

    choices = [('y', True, 'Perform the operation'),

               ('n', False, 'Do not perform the operation')]

  if not choices or not isinstance(choices, list):

    raise errors.ProgrammerError("Invalid choices argument to AskUser")

  for entry in choices:

    if not isinstance(entry, tuple) or len(entry) < 3 or entry[0] == '?':

      raise errors.ProgrammerError("Invalid choices element to AskUser")

  answer = choices[-1][1]

  new_text = []

  for line in text.splitlines():

    new_text.append(textwrap.fill(line, 70, replace_whitespace=False))

  text = "\n".join(new_text)

  try:

    f = file("/dev/tty", "a+")

  except IOError:

    return answer

  try:

    chars = [entry[0] for entry in choices]

    chars[-1] = "[%s]" % chars[-1]

    chars.append('?')

    maps = dict([(entry[0], entry[1]) for entry in choices])

    while True:

      f.write(text)

      f.write('\n')

      f.write("/".join(chars))

      f.write(": ")

      line = f.readline(2).strip().lower()

      if line in maps:

        answer = maps[line]

        break

      elif line == '?':

        for entry in choices:

          f.write(" %s - %s\n" % (entry[0], entry[2]))

        f.write("\n")

        continue

  finally:

    f.close()

  return answer

class JobSubmittedException(Exception):

  """Job was submitted, client should exit.

  This exception has one argument, the ID of the job that was

  submitted. The handler should print this ID.

  This is not an error, just a structured way to exit from clients.

  """

def SendJob(ops, cl=None):

  """Function to submit an opcode without waiting for the results.

  @type ops: list

  @param ops: list of opcodes

  @type cl: luxi.Client

  @param cl: the luxi client to use for communicating with the master;

             if None, a new client will be created

  """

  if cl is None:

    cl = GetClient()

  job_id = cl.SubmitJob(ops)

  return job_id

def PollJob(job_id, cl=None, feedback_fn=None):

  """Function to poll for the result of a job.

  @type job_id: job identified

  @param job_id: the job to poll for results

  @type cl: luxi.Client

  @param cl: the luxi client to use for communicating with the master;

             if None, a new client will be created

  """

  if cl is None:

    cl = GetClient()

  prev_job_info = None

  prev_logmsg_serial = None

  while True:

    result = cl.WaitForJobChange(job_id, ["status"], prev_job_info,

                                 prev_logmsg_serial)

    if not result:

      # job not found, go away!

      raise errors.JobLost("Job with id %s lost" % job_id)

    # Split result, a tuple of (field values, log entries)

    (job_info, log_entries) = result

    (status, ) = job_info

    if log_entries:

      for log_entry in log_entries:

        (serial, timestamp, _, message) = log_entry

        if callable(feedback_fn):

          feedback_fn(log_entry[1:])

        else:

          encoded = utils.SafeEncode(message)

          ToStdout("%s %s", time.ctime(utils.MergeTime(timestamp)), encoded)

        prev_logmsg_serial = max(prev_logmsg_serial, serial)

    # TODO: Handle canceled and archived jobs

    elif status in (constants.JOB_STATUS_SUCCESS,

                    constants.JOB_STATUS_ERROR,

                    constants.JOB_STATUS_CANCELING,

                    constants.JOB_STATUS_CANCELED):

      break

    prev_job_info = job_info

  jobs = cl.QueryJobs([job_id], ["status", "opstatus", "opresult"])

  if not jobs:

    raise errors.JobLost("Job with id %s lost" % job_id)

  status, opstatus, result = jobs[0]

  if status == constants.JOB_STATUS_SUCCESS:

    return result

  elif status in (constants.JOB_STATUS_CANCELING,

                  constants.JOB_STATUS_CANCELED):

    raise errors.OpExecError("Job was canceled")

  else:

    has_ok = False

    for idx, (status, msg) in enumerate(zip(opstatus, result)):

      if status == constants.OP_STATUS_SUCCESS:

        has_ok = True

      elif status == constants.OP_STATUS_ERROR:

        errors.MaybeRaise(msg)

        if has_ok:

          raise errors.OpExecError("partial failure (opcode %d): %s" %

                                   (idx, msg))

        else:

          raise errors.OpExecError(str(msg))

    # default failure mode

    raise errors.OpExecError(result)

def SubmitOpCode(op, cl=None, feedback_fn=None):

  """Legacy function to submit an opcode.

  This is just a simple wrapper over the construction of the processor

  instance. It should be extended to better handle feedback and

  interaction functions.

  """

  if cl is None:

    cl = GetClient()

  job_id = SendJob([op], cl)

  op_results = PollJob(job_id, cl=cl, feedback_fn=feedback_fn)

  return op_results[0]

def SubmitOrSend(op, opts, cl=None, feedback_fn=None):

  """Wrapper around SubmitOpCode or SendJob.

  This function will decide, based on the 'opts' parameter, whether to

  submit and wait for the result of the opcode (and return it), or

  whether to just send the job and print its identifier. It is used in

  order to simplify the implementation of the '--submit' option.

  It will also add the dry-run parameter from the options passed, if true.

  """

  if opts and opts.dry_run:

    op.dry_run = opts.dry_run

  if opts and opts.submit_only:

    job_id = SendJob([op], cl=cl)

    raise JobSubmittedException(job_id)

  else:

    return SubmitOpCode(op, cl=cl, feedback_fn=feedback_fn)

def GetClient():

  # TODO: Cache object?

  try:

    client = luxi.Client()

  except luxi.NoMasterError:

    master, myself = ssconf.GetMasterAndMyself()

    if master != myself:

      raise errors.OpPrereqError("This is not the master node, please connect"

                                 " to node '%s' and rerun the command" %

                                 master)

    else:

      raise

  return client

def FormatError(err):

  """Return a formatted error message for a given error.

  This function takes an exception instance and returns a tuple

  consisting of two values: first, the recommended exit code, and

  second, a string describing the error message (not

  newline-terminated).

  """

  retcode = 1

  obuf = StringIO()

  msg = str(err)

  if isinstance(err, errors.ConfigurationError):

    txt = "Corrupt configuration file: %s" % msg

    logging.error(txt)

    obuf.write(txt + "\n")

    obuf.write("Aborting.")

    retcode = 2

  elif isinstance(err, errors.HooksAbort):

    obuf.write("Failure: hooks execution failed:\n")

    for node, script, out in err.args[0]:

      if out:

        obuf.write("  node: %s, script: %s, output: %s\n" %

                   (node, script, out))

      else:

        obuf.write("  node: %s, script: %s (no output)\n" %

                   (node, script))

  elif isinstance(err, errors.HooksFailure):

    obuf.write("Failure: hooks general failure: %s" % msg)

  elif isinstance(err, errors.ResolverError):

    this_host = utils.HostInfo.SysName()

    if err.args[0] == this_host:

      msg = "Failure: can't resolve my own hostname ('%s')"

    else:

      msg = "Failure: can't resolve hostname '%s'"

    obuf.write(msg % err.args[0])

  elif isinstance(err, errors.OpPrereqError):

    obuf.write("Failure: prerequisites not met for this"

               " operation:\n%s" % msg)

  elif isinstance(err, errors.OpExecError):

    obuf.write("Failure: command execution error:\n%s" % msg)

  elif isinstance(err, errors.TagError):

    obuf.write("Failure: invalid tag(s) given:\n%s" % msg)

  elif isinstance(err, errors.JobQueueDrainError):

    obuf.write("Failure: the job queue is marked for drain and doesn't"

               " accept new requests\n")

  elif isinstance(err, errors.JobQueueFull):

    obuf.write("Failure: the job queue is full and doesn't accept new"

               " job submissions until old jobs are archived\n")

  elif isinstance(err, errors.TypeEnforcementError):

    obuf.write("Parameter Error: %s" % msg)

  elif isinstance(err, errors.ParameterError):

    obuf.write("Failure: unknown/wrong parameter name '%s'" % msg)

  elif isinstance(err, errors.GenericError):

    obuf.write("Unhandled Ganeti error: %s" % msg)

  elif isinstance(err, luxi.NoMasterError):

    obuf.write("Cannot communicate with the master daemon.\nIs it running"

               " and listening for connections?")

  elif isinstance(err, luxi.TimeoutError):

    obuf.write("Timeout while talking to the master daemon. Error:\n"

               "%s" % msg)

  elif isinstance(err, luxi.ProtocolError):

    obuf.write("Unhandled protocol error while talking to the master daemon:\n"

               "%s" % msg)

  elif isinstance(err, JobSubmittedException):

    obuf.write("JobID: %s\n" % err.args[0])

    retcode = 0

  else:

    obuf.write("Unhandled exception: %s" % msg)

  return retcode, obuf.getvalue().rstrip('\n')

def GenericMain(commands, override=None, aliases=None):

  """Generic main function for all the gnt-* commands.

  Arguments:

    - commands: a dictionary with a special structure, see the design doc

                for command line handling.

    - override: if not None, we expect a dictionary with keys that will

                override command line options; this can be used to pass

                options from the scripts to generic functions

    - aliases: dictionary with command aliases {'alias': 'target, ...}

  """

  # save the program name and the entire command line for later logging

  if sys.argv:

    binary = os.path.basename(sys.argv[0]) or sys.argv[0]

    if len(sys.argv) >= 2:

      binary += " " + sys.argv[1]

      old_cmdline = " ".join(sys.argv[2:])

    else:

      old_cmdline = ""

  else:

    binary = "<unknown program>"

    old_cmdline = ""

  if aliases is None:

    aliases = {}

  try:

    func, options, args = _ParseArgs(sys.argv, commands, aliases)

  except errors.ParameterError, err:

    result, err_msg = FormatError(err)

    ToStderr(err_msg)

    return 1

  if func is None: # parse error

    return 1

  if override is not None:

    for key, val in override.iteritems():

      setattr(options, key, val)

  utils.SetupLogging(constants.LOG_COMMANDS, debug=options.debug,

                     stderr_logging=True, program=binary)

  if old_cmdline:

    logging.info("run with arguments '%s'", old_cmdline)

  else:

    logging.info("run with no arguments")

  try:

    result = func(options, args)

  except (errors.GenericError, luxi.ProtocolError,

          JobSubmittedException), err:

    result, err_msg = FormatError(err)

    logging.exception("Error during command processing")

    ToStderr(err_msg)

  return result

def GenerateTable(headers, fields, separator, data,

                  numfields=None, unitfields=None,

                  units=None):

  """Prints a table with headers and different fields.

  @type headers: dict

  @param headers: dictionary mapping field names to headers for

      the table

  @type fields: list

  @param fields: the field names corresponding to each row in

      the data field

  @param separator: the separator to be used; if this is None,

      the default 'smart' algorithm is used which computes optimal

      field width, otherwise just the separator is used between